Merge remote-tracking branch 'remotes/huth-gitlab/tags/pull-request-2020-10-26' into staging

* qtest fixes (e.g. memory leaks)
* Fix for Xen dummy cpu loop (which happened due to qtest accel rework)
* Introduction of the generic device fuzzer
* Run more check-acceptance tests in the gitlab-CI

# gpg: Signature made Mon 26 Oct 2020 09:34:04 GMT
# gpg:                using RSA key 27B88847EEE0250118F3EAB92ED9D774FE702DB5
# gpg:                issuer "thuth@redhat.com"
# gpg: Good signature from "Thomas Huth <th.huth@gmx.de>" [full]
# gpg:                 aka "Thomas Huth <thuth@redhat.com>" [full]
# gpg:                 aka "Thomas Huth <huth@tuxfamily.org>" [full]
# gpg:                 aka "Thomas Huth <th.huth@posteo.de>" [unknown]
# Primary key fingerprint: 27B8 8847 EEE0 2501 18F3  EAB9 2ED9 D774 FE70 2DB5

* remotes/huth-gitlab/tags/pull-request-2020-10-26: (31 commits)
  tests/acceptance: Use .ppm extention for Portable PixMap files
  tests/acceptance: Remove unused import
  test/docker/dockerfiles: Add missing packages for acceptance tests
  tests/acceptance: Enable AVOCADO_ALLOW_UNTRUSTED_CODE in the gitlab-CI
  test/acceptance: Remove the CONTINUOUS_INTEGRATION tags
  tests/acceptance/ppc_prep_40p: Fix the URL to the NetBSD-4.0 archive
  scripts/oss-fuzz: ignore the generic-fuzz target
  scripts/oss-fuzz: use hardlinks instead of copying
  fuzz: register predefined generic-fuzz configs
  fuzz: add generic-fuzz configs for oss-fuzz
  fuzz: add an "opaque" to the FuzzTarget struct
  fuzz: Add instructions for using generic-fuzz
  scripts/oss-fuzz: Add crash trace minimization script
  scripts/oss-fuzz: Add script to reorder a generic-fuzzer trace
  fuzz: add a crossover function to generic-fuzzer
  fuzz: add a DISABLE_PCI op to generic-fuzzer
  fuzz: Add support for custom crossover functions
  fuzz: Add fuzzer callbacks to DMA-read functions
  fuzz: Declare DMA Read callback function
  fuzz: Add DMA support to the generic-fuzzer
  ...

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

31 files changed, 1550 insertions, 65 deletions

diff --git a/.gitlab-ci.yml b/.gitlab-ci.yml
index 66ad7aa..5d6773e 100644
--- a/.gitlab-ci.yml
+++ b/.gitlab-ci.yml
@@ -66,6 +66,7 @@ include:
     - if [ -d ${CI_PROJECT_DIR}/avocado-cache ]; then
         du -chs ${CI_PROJECT_DIR}/avocado-cache ;
       fi
+    - export AVOCADO_ALLOW_UNTRUSTED_CODE=1
   after_script:
     - cd build
     - python3 -c 'import json; r = json.load(open("tests/results/latest/results.json")); [print(t["logfile"]) for t in r["tests"] if t["status"] not in ("PASS", "SKIP", "CANCEL")]' | xargs cat
diff --git a/accel/qtest/qtest-cpus.c b/accel/dummy-cpus.c
index 7c5399e..10429fd 100644
--- a/accel/qtest/qtest-cpus.c
+++ b/accel/dummy-cpus.c
@@ -1,5 +1,5 @@
 /*
- * QTest accelerator code
+ * Dummy cpu thread code
  *
  * Copyright IBM, Corp. 2011
  *
@@ -13,26 +13,13 @@
 
 #include "qemu/osdep.h"
 #include "qemu/rcu.h"
-#include "qapi/error.h"
-#include "qemu/module.h"
-#include "qemu/option.h"
-#include "qemu/config-file.h"
-#include "sysemu/accel.h"
-#include "sysemu/qtest.h"
 #include "sysemu/cpus.h"
-#include "sysemu/cpu-timers.h"
 #include "qemu/guest-random.h"
 #include "qemu/main-loop.h"
 #include "hw/core/cpu.h"
 
-#include "qtest-cpus.h"
-
-static void *qtest_cpu_thread_fn(void *arg)
+static void *dummy_cpu_thread_fn(void *arg)
 {
-#ifdef _WIN32
-    error_report("qtest is not supported under Windows");
-    exit(1);
-#else
     CPUState *cpu = arg;
     sigset_t waitset;
     int r;
@@ -69,10 +56,9 @@ static void *qtest_cpu_thread_fn(void *arg)
     qemu_mutex_unlock_iothread();
     rcu_unregister_thread();
     return NULL;
-#endif
 }
 
-static void qtest_start_vcpu_thread(CPUState *cpu)
+void dummy_start_vcpu_thread(CPUState *cpu)
 {
     char thread_name[VCPU_THREAD_NAME_SIZE];
 
@@ -81,11 +67,6 @@ static void qtest_start_vcpu_thread(CPUState *cpu)
     qemu_cond_init(cpu->halt_cond);
     snprintf(thread_name, VCPU_THREAD_NAME_SIZE, "CPU %d/DUMMY",
              cpu->cpu_index);
-    qemu_thread_create(cpu->thread, thread_name, qtest_cpu_thread_fn, cpu,
+    qemu_thread_create(cpu->thread, thread_name, dummy_cpu_thread_fn, cpu,
                        QEMU_THREAD_JOINABLE);
 }
-
-const CpusAccel qtest_cpus = {
-    .create_vcpu_thread = qtest_start_vcpu_thread,
-    .get_virtual_clock = qtest_get_virtual_clock,
-};
diff --git a/accel/meson.build b/accel/meson.build
index bb00d0f..b26cca2 100644
--- a/accel/meson.build
+++ b/accel/meson.build
@@ -5,3 +5,11 @@ subdir('kvm')
 subdir('tcg')
 subdir('xen')
 subdir('stubs')
+
+dummy_ss = ss.source_set()
+dummy_ss.add(files(
+  'dummy-cpus.c',
+))
+
+specific_ss.add_all(when: ['CONFIG_SOFTMMU', 'CONFIG_POSIX'], if_true: dummy_ss)
+specific_ss.add_all(when: ['CONFIG_XEN'], if_true: dummy_ss)
diff --git a/accel/qtest/meson.build b/accel/qtest/meson.build
index e477cb2..a2f3276 100644
--- a/accel/qtest/meson.build
+++ b/accel/qtest/meson.build
@@ -1,7 +1,6 @@
 qtest_ss = ss.source_set()
 qtest_ss.add(files(
   'qtest.c',
-  'qtest-cpus.c',
 ))
 
 specific_ss.add_all(when: ['CONFIG_SOFTMMU', 'CONFIG_POSIX'], if_true: qtest_ss)
diff --git a/accel/qtest/qtest-cpus.h b/accel/qtest/qtest-cpus.h
deleted file mode 100644
index 739519a..0000000
--- a/accel/qtest/qtest-cpus.h
+++ /dev/null
@@ -1,17 +0,0 @@
-/*
- * Accelerator CPUS Interface
- *
- * Copyright 2020 SUSE LLC
- *
- * This work is licensed under the terms of the GNU GPL, version 2 or later.
- * See the COPYING file in the top-level directory.
- */
-
-#ifndef QTEST_CPUS_H
-#define QTEST_CPUS_H
-
-#include "sysemu/cpus.h"
-
-extern const CpusAccel qtest_cpus;
-
-#endif /* QTEST_CPUS_H */
diff --git a/accel/qtest/qtest.c b/accel/qtest/qtest.c
index 537e8b4..b282cea 100644
--- a/accel/qtest/qtest.c
+++ b/accel/qtest/qtest.c
@@ -25,7 +25,10 @@
 #include "qemu/main-loop.h"
 #include "hw/core/cpu.h"
 
-#include "qtest-cpus.h"
+const CpusAccel qtest_cpus = {
+    .create_vcpu_thread = dummy_start_vcpu_thread,
+    .get_virtual_clock = qtest_get_virtual_clock,
+};
 
 static int qtest_init_accel(MachineState *ms)
 {
diff --git a/accel/xen/xen-all.c b/accel/xen/xen-all.c
index 60b971d..878a408 100644
--- a/accel/xen/xen-all.c
+++ b/accel/xen/xen-all.c
@@ -16,6 +16,7 @@
 #include "hw/xen/xen_pt.h"
 #include "chardev/char.h"
 #include "sysemu/accel.h"
+#include "sysemu/cpus.h"
 #include "sysemu/xen.h"
 #include "sysemu/runstate.h"
 #include "migration/misc.h"
@@ -153,6 +154,10 @@ static void xen_setup_post(MachineState *ms, AccelState *accel)
     }
 }
 
+const CpusAccel xen_cpus = {
+    .create_vcpu_thread = dummy_start_vcpu_thread,
+};
+
 static int xen_init(MachineState *ms)
 {
     MachineClass *mc = MACHINE_GET_CLASS(ms);
@@ -180,6 +185,9 @@ static int xen_init(MachineState *ms)
      * opt out of system RAM being allocated by generic code
      */
     mc->default_ram_id = NULL;
+
+    cpus_register_accel(&xen_cpus);
+
     return 0;
 }
 
diff --git a/docs/devel/fuzzing.txt b/docs/devel/fuzzing.txt
index 96d71c9..03585c1 100644
--- a/docs/devel/fuzzing.txt
+++ b/docs/devel/fuzzing.txt
@@ -125,6 +125,45 @@ provided by libfuzzer. Libfuzzer passes a byte array and length. Commonly the
 fuzzer loops over the byte-array interpreting it as a list of qtest commands,
 addresses, or values.
 
+== The Generic Fuzzer ==
+Writing a fuzz target can be a lot of effort (especially if a device driver has
+not be built-out within libqos). Many devices can be fuzzed to some degree,
+without any device-specific code, using the generic-fuzz target.
+
+The generic-fuzz target is capable of fuzzing devices over their PIO, MMIO,
+and DMA input-spaces. To apply the generic-fuzz to a device, we need to define
+two env-variables, at minimum:
+
+QEMU_FUZZ_ARGS= is the set of QEMU arguments used to configure a machine, with
+the device attached. For example, if we want to fuzz the virtio-net device
+attached to a pc-i440fx machine, we can specify:
+QEMU_FUZZ_ARGS="-M pc -nodefaults -netdev user,id=user0 \
+                -device virtio-net,netdev=user0"
+
+QEMU_FUZZ_OBJECTS= is a set of space-delimited strings used to identify the
+MemoryRegions that will be fuzzed. These strings are compared against
+MemoryRegion names and MemoryRegion owner names, to decide whether each
+MemoryRegion should be fuzzed. These strings support globbing. For the
+virtio-net example, we could use QEMU_FUZZ_OBJECTS=
+ * 'virtio-net'
+ * 'virtio*'
+ * 'virtio* pcspk' (Fuzz the virtio devices and the PC speaker...)
+ * '*' (Fuzz the whole machine)
+
+The "info mtree" and "info qom-tree" monitor commands can be especially useful
+for identifying the MemoryRegion and Object names used for matching.
+
+As a generic rule-of-thumb, the more MemoryRegions/Devices we match, the greater
+the input-space, and the smaller the probability of finding crashing inputs for
+individual devices. As such, it is usually a good idea to limit the fuzzer to
+only a few MemoryRegions.
+
+To ensure that these env variables have been configured correctly, we can use:
+
+./qemu-fuzz-i386 --fuzz-target=generic-fuzz -runs=0
+
+The output should contain a complete list of matched MemoryRegions.
+
 = Implementation Details =
 
 == The Fuzzer's Lifecycle ==
diff --git a/include/exec/memory.h b/include/exec/memory.h
index 622207b..aff6ef7 100644
--- a/include/exec/memory.h
+++ b/include/exec/memory.h
@@ -42,6 +42,21 @@ typedef struct IOMMUMemoryRegionClass IOMMUMemoryRegionClass;
 DECLARE_OBJ_CHECKERS(IOMMUMemoryRegion, IOMMUMemoryRegionClass,
                      IOMMU_MEMORY_REGION, TYPE_IOMMU_MEMORY_REGION)
 
+#ifdef CONFIG_FUZZ
+void fuzz_dma_read_cb(size_t addr,
+                      size_t len,
+                      MemoryRegion *mr,
+                      bool is_write);
+#else
+static inline void fuzz_dma_read_cb(size_t addr,
+                                    size_t len,
+                                    MemoryRegion *mr,
+                                    bool is_write)
+{
+    /* Do Nothing */
+}
+#endif
+
 extern bool global_dirty_log;
 
 typedef struct MemoryRegionOps MemoryRegionOps;
@@ -719,6 +734,11 @@ static inline FlatView *address_space_to_flatview(AddressSpace *as)
     return qatomic_rcu_read(&as->current_map);
 }
 
+typedef int (*flatview_cb)(Int128 start,
+                           Int128 len,
+                           const MemoryRegion*, void*);
+
+void flatview_for_each_range(FlatView *fv, flatview_cb cb , void *opaque);
 
 /**
  * struct MemoryRegionSection: describes a fragment of a #MemoryRegion
@@ -2442,6 +2462,7 @@ address_space_read_cached(MemoryRegionCache *cache, hwaddr addr,
                           void *buf, hwaddr len)
 {
     assert(addr < cache->len && len <= cache->len - addr);
+    fuzz_dma_read_cb(cache->xlat + addr, len, cache->mrs.mr, false);
     if (likely(cache->ptr)) {
         memcpy(buf, cache->ptr + addr, len);
         return MEMTX_OK;
diff --git a/include/exec/memory_ldst_cached.h.inc b/include/exec/memory_ldst_cached.h.inc
index fd4bbb4..aff5740 100644
--- a/include/exec/memory_ldst_cached.h.inc
+++ b/include/exec/memory_ldst_cached.h.inc
@@ -28,6 +28,7 @@ static inline uint32_t ADDRESS_SPACE_LD_CACHED(l)(MemoryRegionCache *cache,
     hwaddr addr, MemTxAttrs attrs, MemTxResult *result)
 {
     assert(addr < cache->len && 4 <= cache->len - addr);
+    fuzz_dma_read_cb(cache->xlat + addr, 4, cache->mrs.mr, false);
     if (likely(cache->ptr)) {
         return LD_P(l)(cache->ptr + addr);
     } else {
@@ -39,6 +40,7 @@ static inline uint64_t ADDRESS_SPACE_LD_CACHED(q)(MemoryRegionCache *cache,
     hwaddr addr, MemTxAttrs attrs, MemTxResult *result)
 {
     assert(addr < cache->len && 8 <= cache->len - addr);
+    fuzz_dma_read_cb(cache->xlat + addr, 8, cache->mrs.mr, false);
     if (likely(cache->ptr)) {
         return LD_P(q)(cache->ptr + addr);
     } else {
@@ -50,6 +52,7 @@ static inline uint32_t ADDRESS_SPACE_LD_CACHED(uw)(MemoryRegionCache *cache,
     hwaddr addr, MemTxAttrs attrs, MemTxResult *result)
 {
     assert(addr < cache->len && 2 <= cache->len - addr);
+    fuzz_dma_read_cb(cache->xlat + addr, 2, cache->mrs.mr, false);
     if (likely(cache->ptr)) {
         return LD_P(uw)(cache->ptr + addr);
     } else {
diff --git a/include/sysemu/cpus.h b/include/sysemu/cpus.h
index 2316859..e815672 100644
--- a/include/sysemu/cpus.h
+++ b/include/sysemu/cpus.h
@@ -25,6 +25,9 @@ typedef struct CpusAccel {
 /* register accel-specific cpus interface implementation */
 void cpus_register_accel(const CpusAccel *i);
 
+/* Create a dummy vcpu for CpusAccel->create_vcpu_thread */
+void dummy_start_vcpu_thread(CPUState *);
+
 /* interface available for cpus accelerator threads */
 
 /* For temporary buffers for forming a name */
diff --git a/memory_ldst.c.inc b/memory_ldst.c.inc
index c54aee4..8d45d2e 100644
--- a/memory_ldst.c.inc
+++ b/memory_ldst.c.inc
@@ -42,6 +42,7 @@ static inline uint32_t glue(address_space_ldl_internal, SUFFIX)(ARG1_DECL,
                                         MO_32 | devend_memop(endian), attrs);
     } else {
         /* RAM case */
+        fuzz_dma_read_cb(addr, 4, mr, false);
         ptr = qemu_map_ram_ptr(mr->ram_block, addr1);
         switch (endian) {
         case DEVICE_LITTLE_ENDIAN:
@@ -110,6 +111,7 @@ static inline uint64_t glue(address_space_ldq_internal, SUFFIX)(ARG1_DECL,
                                         MO_64 | devend_memop(endian), attrs);
     } else {
         /* RAM case */
+        fuzz_dma_read_cb(addr, 8, mr, false);
         ptr = qemu_map_ram_ptr(mr->ram_block, addr1);
         switch (endian) {
         case DEVICE_LITTLE_ENDIAN:
@@ -175,6 +177,7 @@ uint32_t glue(address_space_ldub, SUFFIX)(ARG1_DECL,
         r = memory_region_dispatch_read(mr, addr1, &val, MO_8, attrs);
     } else {
         /* RAM case */
+        fuzz_dma_read_cb(addr, 1, mr, false);
         ptr = qemu_map_ram_ptr(mr->ram_block, addr1);
         val = ldub_p(ptr);
         r = MEMTX_OK;
@@ -212,6 +215,7 @@ static inline uint32_t glue(address_space_lduw_internal, SUFFIX)(ARG1_DECL,
                                         MO_16 | devend_memop(endian), attrs);
     } else {
         /* RAM case */
+        fuzz_dma_read_cb(addr, 2, mr, false);
         ptr = qemu_map_ram_ptr(mr->ram_block, addr1);
         switch (endian) {
         case DEVICE_LITTLE_ENDIAN:
diff --git a/scripts/oss-fuzz/build.sh b/scripts/oss-fuzz/build.sh
index 0c3ca9e..fcae4a0 100755
--- a/scripts/oss-fuzz/build.sh
+++ b/scripts/oss-fuzz/build.sh
@@ -62,6 +62,9 @@ fi
 
 mkdir -p "$DEST_DIR/lib/"  # Copy the shared libraries here
 
+mkdir -p "$DEST_DIR/bin/"  # Copy executables that shouldn't
+                           # be treated as fuzzers by oss-fuzz here
+
 # Build once to get the list of dynamic lib paths, and copy them over
 ../configure --disable-werror --cc="$CC" --cxx="$CXX" --enable-fuzzing \
     --prefix="$DEST_DIR" --bindir="$DEST_DIR" --datadir="$DEST_DIR/data/" \
@@ -88,13 +91,22 @@ make "-j$(nproc)" qemu-fuzz-i386 V=1
 # Copy over the datadir
 cp  -r ../pc-bios/ "$DEST_DIR/pc-bios"
 
+cp "./qemu-fuzz-i386" "$DEST_DIR/bin/"
+
 # Run the fuzzer with no arguments, to print the help-string and get the list
 # of available fuzz-targets. Copy over the qemu-fuzz-i386, naming it according
 # to each available fuzz target (See 05509c8e6d fuzz: select fuzz target using
 # executable name)
 for target in $(./qemu-fuzz-i386 | awk '$1 ~ /\*/  {print $2}');
 do
-    cp qemu-fuzz-i386 "$DEST_DIR/qemu-fuzz-i386-target-$target"
+    # Ignore the generic-fuzz target, as it requires some environment variables
+    # to be configured. We have some generic-fuzz-{pc-q35, floppy, ...} targets
+    # that are thin wrappers around this target that set the required
+    # environment variables according to predefined configs.
+    if [ "$target" != "generic-fuzz" ]; then
+        ln  "$DEST_DIR/bin/qemu-fuzz-i386" \
+            "$DEST_DIR/qemu-fuzz-i386-target-$target"
+    fi
 done
 
 echo "Done. The fuzzers are located in $DEST_DIR"
diff --git a/scripts/oss-fuzz/minimize_qtest_trace.py b/scripts/oss-fuzz/minimize_qtest_trace.py
new file mode 100755
index 0000000..5e405a0
--- /dev/null
+++ b/scripts/oss-fuzz/minimize_qtest_trace.py
@@ -0,0 +1,157 @@
+#!/usr/bin/env python3
+# -*- coding: utf-8 -*-
+
+"""
+This takes a crashing qtest trace and tries to remove superflous operations
+"""
+
+import sys
+import os
+import subprocess
+import time
+import struct
+
+QEMU_ARGS = None
+QEMU_PATH = None
+TIMEOUT = 5
+CRASH_TOKEN = None
+
+write_suffix_lookup = {"b": (1, "B"),
+                       "w": (2, "H"),
+                       "l": (4, "L"),
+                       "q": (8, "Q")}
+
+def usage():
+    sys.exit("""\
+Usage: QEMU_PATH="/path/to/qemu" QEMU_ARGS="args" {} input_trace output_trace
+By default, will try to use the second-to-last line in the output to identify
+whether the crash occred. Optionally, manually set a string that idenitifes the
+crash by setting CRASH_TOKEN=
+""".format((sys.argv[0])))
+
+def check_if_trace_crashes(trace, path):
+    global CRASH_TOKEN
+    with open(path, "w") as tracefile:
+        tracefile.write("".join(trace))
+
+    rc = subprocess.Popen("timeout -s 9 {timeout}s {qemu_path} {qemu_args} 2>&1\
+    < {trace_path}".format(timeout=TIMEOUT,
+                           qemu_path=QEMU_PATH,
+                           qemu_args=QEMU_ARGS,
+                           trace_path=path),
+                          shell=True,
+                          stdin=subprocess.PIPE,
+                          stdout=subprocess.PIPE)
+    stdo = rc.communicate()[0]
+    output = stdo.decode('unicode_escape')
+    if rc.returncode == 137:    # Timed Out
+        return False
+    if len(output.splitlines()) < 2:
+        return False
+
+    if CRASH_TOKEN is None:
+        CRASH_TOKEN = output.splitlines()[-2]
+
+    return CRASH_TOKEN in output
+
+
+def minimize_trace(inpath, outpath):
+    global TIMEOUT
+    with open(inpath) as f:
+        trace = f.readlines()
+    start = time.time()
+    if not check_if_trace_crashes(trace, outpath):
+        sys.exit("The input qtest trace didn't cause a crash...")
+    end = time.time()
+    print("Crashed in {} seconds".format(end-start))
+    TIMEOUT = (end-start)*5
+    print("Setting the timeout for {} seconds".format(TIMEOUT))
+    print("Identifying Crashes by this string: {}".format(CRASH_TOKEN))
+
+    i = 0
+    newtrace = trace[:]
+    # For each line
+    while i < len(newtrace):
+        # 1.) Try to remove it completely and reproduce the crash. If it works,
+        # we're done.
+        prior = newtrace[i]
+        print("Trying to remove {}".format(newtrace[i]))
+        # Try to remove the line completely
+        newtrace[i] = ""
+        if check_if_trace_crashes(newtrace, outpath):
+            i += 1
+            continue
+        newtrace[i] = prior
+
+        # 2.) Try to replace write{bwlq} commands with a write addr, len
+        # command. Since this can require swapping endianness, try both LE and
+        # BE options. We do this, so we can "trim" the writes in (3)
+        if (newtrace[i].startswith("write") and not
+            newtrace[i].startswith("write ")):
+            suffix = newtrace[i].split()[0][-1]
+            assert(suffix in write_suffix_lookup)
+            addr = int(newtrace[i].split()[1], 16)
+            value = int(newtrace[i].split()[2], 16)
+            for endianness in ['<', '>']:
+                data = struct.pack("{end}{size}".format(end=endianness,
+                                   size=write_suffix_lookup[suffix][1]),
+                                   value)
+                newtrace[i] = "write {addr} {size} 0x{data}\n".format(
+                    addr=hex(addr),
+                    size=hex(write_suffix_lookup[suffix][0]),
+                    data=data.hex())
+                if(check_if_trace_crashes(newtrace, outpath)):
+                    break
+            else:
+                newtrace[i] = prior
+
+        # 3.) If it is a qtest write command: write addr len data, try to split
+        # it into two separate write commands. If splitting the write down the
+        # middle does not work, try to move the pivot "left" and retry, until
+        # there is no space left. The idea is to prune unneccessary bytes from
+        # long writes, while accommodating arbitrary MemoryRegion access sizes
+        # and alignments.
+        if newtrace[i].startswith("write "):
+            addr = int(newtrace[i].split()[1], 16)
+            length = int(newtrace[i].split()[2], 16)
+            data = newtrace[i].split()[3][2:]
+            if length > 1:
+                leftlength = int(length/2)
+                rightlength = length - leftlength
+                newtrace.insert(i+1, "")
+                while leftlength > 0:
+                    newtrace[i] = "write {addr} {size} 0x{data}\n".format(
+                            addr=hex(addr),
+                            size=hex(leftlength),
+                            data=data[:leftlength*2])
+                    newtrace[i+1] = "write {addr} {size} 0x{data}\n".format(
+                            addr=hex(addr+leftlength),
+                            size=hex(rightlength),
+                            data=data[leftlength*2:])
+                    if check_if_trace_crashes(newtrace, outpath):
+                        break
+                    else:
+                        leftlength -= 1
+                        rightlength += 1
+                if check_if_trace_crashes(newtrace, outpath):
+                    i -= 1
+                else:
+                    newtrace[i] = prior
+                    del newtrace[i+1]
+        i += 1
+    check_if_trace_crashes(newtrace, outpath)
+
+
+if __name__ == '__main__':
+    if len(sys.argv) < 3:
+        usage()
+
+    QEMU_PATH = os.getenv("QEMU_PATH")
+    QEMU_ARGS = os.getenv("QEMU_ARGS")
+    if QEMU_PATH is None or QEMU_ARGS is None:
+        usage()
+    # if "accel" not in QEMU_ARGS:
+    #     QEMU_ARGS += " -accel qtest"
+    CRASH_TOKEN = os.getenv("CRASH_TOKEN")
+    QEMU_ARGS += " -qtest stdio -monitor none -serial none "
+    minimize_trace(sys.argv[1], sys.argv[2])
diff --git a/scripts/oss-fuzz/reorder_fuzzer_qtest_trace.py b/scripts/oss-fuzz/reorder_fuzzer_qtest_trace.py
new file mode 100755
index 0000000..890e1de
--- /dev/null
+++ b/scripts/oss-fuzz/reorder_fuzzer_qtest_trace.py
@@ -0,0 +1,103 @@
+#!/usr/bin/env python3
+# -*- coding: utf-8 -*-
+
+"""
+Use this to convert qtest log info from a generic fuzzer input into a qtest
+trace that you can feed into a standard qemu-system process. Example usage:
+
+QEMU_FUZZ_ARGS="-machine q35,accel=qtest" QEMU_FUZZ_OBJECTS="*" \
+        ./i386-softmmu/qemu-fuzz-i386 --fuzz-target=generic-pci-fuzz
+# .. Finds some crash
+QTEST_LOG=1 FUZZ_SERIALIZE_QTEST=1 \
+QEMU_FUZZ_ARGS="-machine q35,accel=qtest" QEMU_FUZZ_OBJECTS="*" \
+        ./i386-softmmu/qemu-fuzz-i386 --fuzz-target=generic-pci-fuzz
+        /path/to/crash 2> qtest_log_output
+scripts/oss-fuzz/reorder_fuzzer_qtest_trace.py qtest_log_output > qtest_trace
+./i386-softmmu/qemu-fuzz-i386 -machine q35,accel=qtest \
+        -qtest stdin < qtest_trace
+
+### Details ###
+
+Some fuzzer make use of hooks that allow us to populate some memory range, just
+before a DMA read from that range. This means that the fuzzer can produce
+activity that looks like:
+    [start] read from mmio addr
+    [end]   read from mmio addr
+    [start] write to pio addr
+        [start] fill a DMA buffer just in time
+        [end]   fill a DMA buffer just in time
+        [start] fill a DMA buffer just in time
+        [end]   fill a DMA buffer just in time
+    [end]   write to pio addr
+    [start] read from mmio addr
+    [end]   read from mmio addr
+
+We annotate these "nested" DMA writes, so with QTEST_LOG=1 the QTest trace
+might look something like:
+[R +0.028431] readw 0x10000
+[R +0.028434] outl 0xc000 0xbeef  # Triggers a DMA read from 0xbeef and 0xbf00
+[DMA][R +0.034639] write 0xbeef 0x2 0xAAAA
+[DMA][R +0.034639] write 0xbf00 0x2 0xBBBB
+[R +0.028431] readw 0xfc000
+
+This script would reorder the above trace so it becomes:
+readw 0x10000
+write 0xbeef 0x2 0xAAAA
+write 0xbf00 0x2 0xBBBB
+outl 0xc000 0xbeef
+readw 0xfc000
+
+I.e. by the time, 0xc000 tries to read from DMA, those DMA buffers have already
+been set up, removing the need for the DMA hooks. We can simply provide this
+reordered trace via -qtest stdio to reproduce the input
+
+Note: this won't work for traces where the device tries to read from the same
+DMA region twice in between MMIO/PIO commands. E.g:
+    [R +0.028434] outl 0xc000 0xbeef
+    [DMA][R +0.034639] write 0xbeef 0x2 0xAAAA
+    [DMA][R +0.034639] write 0xbeef 0x2 0xBBBB
+
+The fuzzer will annotate suspected double-fetches with [DOUBLE-FETCH]. This
+script looks for these tags and warns the users that the resulting trace might
+not reproduce the bug.
+"""
+
+import sys
+
+__author__     = "Alexander Bulekov <alxndr@bu.edu>"
+__copyright__  = "Copyright (C) 2020, Red Hat, Inc."
+__license__    = "GPL version 2 or (at your option) any later version"
+
+__maintainer__ = "Alexander Bulekov"
+__email__      = "alxndr@bu.edu"
+
+
+def usage():
+    sys.exit("Usage: {} /path/to/qtest_log_output".format((sys.argv[0])))
+
+
+def main(filename):
+    with open(filename, "r") as f:
+        trace = f.readlines()
+
+    # Leave only lines that look like logged qtest commands
+    trace[:] = [x.strip() for x in trace if "[R +" in x
+                or "[S +" in x and "CLOSED" not in x]
+
+    for i in range(len(trace)):
+        if i+1 < len(trace):
+            if "[DMA]" in trace[i+1]:
+                if "[DOUBLE-FETCH]" in trace[i+1]:
+                    sys.stderr.write("Warning: Likely double fetch on line"
+                                     "{}.\n There will likely be problems "
+                                     "reproducing behavior with the "
+                                     "resulting qtest trace\n\n".format(i+1))
+                trace[i], trace[i+1] = trace[i+1], trace[i]
+    for line in trace:
+        print(line.split("]")[-1].strip())
+
+
+if __name__ == '__main__':
+    if len(sys.argv) == 1:
+        usage()
+    main(sys.argv[1])
diff --git a/softmmu/memory.c b/softmmu/memory.c
index 403ff3a..ee4a6bc 100644
--- a/softmmu/memory.c
+++ b/softmmu/memory.c
@@ -656,6 +656,19 @@ static void render_memory_region(FlatView *view,
     }
 }
 
+void flatview_for_each_range(FlatView *fv, flatview_cb cb , void *opaque)
+{
+    FlatRange *fr;
+
+    assert(fv);
+    assert(cb);
+
+    FOR_EACH_FLAT_RANGE(fr, fv) {
+        if (cb(fr->addr.start, fr->addr.size, fr->mr, opaque))
+            break;
+    }
+}
+
 static MemoryRegion *memory_region_get_flatview_root(MemoryRegion *mr)
 {
     while (mr->enabled) {
@@ -1420,6 +1433,7 @@ MemTxResult memory_region_dispatch_read(MemoryRegion *mr,
     unsigned size = memop_size(op);
     MemTxResult r;
 
+    fuzz_dma_read_cb(addr, size, mr, false);
     if (!memory_region_access_valid(mr, addr, size, false, attrs)) {
         *pval = unassigned_mem_read(mr, addr, size);
         return MEMTX_DECODE_ERROR;
@@ -3233,6 +3247,19 @@ void memory_region_init_rom_device(MemoryRegion *mr,
     vmstate_register_ram(mr, owner_dev);
 }
 
+/*
+ * Support softmmu builds with CONFIG_FUZZ using a weak symbol and a stub for
+ * the fuzz_dma_read_cb callback
+ */
+#ifdef CONFIG_FUZZ
+void __attribute__((weak)) fuzz_dma_read_cb(size_t addr,
+                      size_t len,
+                      MemoryRegion *mr,
+                      bool is_write)
+{
+}
+#endif
+
 static const TypeInfo memory_region_info = {
     .parent             = TYPE_OBJECT,
     .name               = TYPE_MEMORY_REGION,
diff --git a/softmmu/physmem.c b/softmmu/physmem.c
index e319fb2..a9adedb 100644
--- a/softmmu/physmem.c
+++ b/softmmu/physmem.c
@@ -2832,6 +2832,7 @@ MemTxResult flatview_read_continue(FlatView *fv, hwaddr addr,
             stn_he_p(buf, l, val);
         } else {
             /* RAM case */
+            fuzz_dma_read_cb(addr, len, mr, false);
             ram_ptr = qemu_ram_ptr_length(mr->ram_block, addr1, &l, false);
             memcpy(buf, ram_ptr, l);
         }
@@ -3192,6 +3193,7 @@ void *address_space_map(AddressSpace *as,
     memory_region_ref(mr);
     *plen = flatview_extend_translation(fv, addr, len, mr, xlat,
                                         l, is_write, attrs);
+    fuzz_dma_read_cb(addr, *plen, mr, is_write);
     ptr = qemu_ram_ptr_length(mr->ram_block, xlat, plen, true);
 
     return ptr;
diff --git a/tests/acceptance/machine_m68k_nextcube.py b/tests/acceptance/machine_m68k_nextcube.py
index 32cf571..2baba5f 100644
--- a/tests/acceptance/machine_m68k_nextcube.py
+++ b/tests/acceptance/machine_m68k_nextcube.py
@@ -9,7 +9,6 @@ import os
 import re
 import time
 import logging
-import distutils.spawn
 
 from avocado_qemu import Test
 from avocado import skipUnless
@@ -70,7 +69,7 @@ class NextCubeMachine(Test):
 
     @skipUnless(PIL_AVAILABLE, 'Python PIL not installed')
     def test_bootrom_framebuffer_size(self):
-        screenshot_path = os.path.join(self.workdir, "dump.png")
+        screenshot_path = os.path.join(self.workdir, "dump.ppm")
         self.check_bootrom_framebuffer(screenshot_path)
 
         width, height = Image.open(screenshot_path).size
@@ -79,7 +78,7 @@ class NextCubeMachine(Test):
 
     @skipUnless(tesseract_available(3), 'tesseract v3 OCR tool not available')
     def test_bootrom_framebuffer_ocr_with_tesseract_v3(self):
-        screenshot_path = os.path.join(self.workdir, "dump.png")
+        screenshot_path = os.path.join(self.workdir, "dump.ppm")
         self.check_bootrom_framebuffer(screenshot_path)
 
         console_logger = logging.getLogger('console')
@@ -95,7 +94,7 @@ class NextCubeMachine(Test):
     # that it is still alpha-level software.
     @skipUnless(tesseract_available(4), 'tesseract v4 OCR tool not available')
     def test_bootrom_framebuffer_ocr_with_tesseract_v4(self):
-        screenshot_path = os.path.join(self.workdir, "dump.png")
+        screenshot_path = os.path.join(self.workdir, "dump.ppm")
         self.check_bootrom_framebuffer(screenshot_path)
 
         console_logger = logging.getLogger('console')
diff --git a/tests/acceptance/ppc_prep_40p.py b/tests/acceptance/ppc_prep_40p.py
index 1515561..96ba13b 100644
--- a/tests/acceptance/ppc_prep_40p.py
+++ b/tests/acceptance/ppc_prep_40p.py
@@ -22,7 +22,6 @@ class IbmPrep40pMachine(Test):
     # All rights reserved.
     # U.S. Government Users Restricted Rights - Use, duplication or disclosure
     # restricted by GSA ADP Schedule Contract with IBM Corp.
-    @skipIf(os.getenv('CONTINUOUS_INTEGRATION'), 'Running on Travis-CI')
     @skipUnless(os.getenv('AVOCADO_ALLOW_UNTRUSTED_CODE'), 'untrusted code')
     def test_factory_firmware_and_netbsd(self):
         """
@@ -35,7 +34,7 @@ class IbmPrep40pMachine(Test):
                     '7020-40p/P12H0456.IMG')
         bios_hash = '1775face4e6dc27f3a6ed955ef6eb331bf817f03'
         bios_path = self.fetch_asset(bios_url, asset_hash=bios_hash)
-        drive_url = ('https://cdn.netbsd.org/pub/NetBSD/NetBSD-archive/'
+        drive_url = ('https://archive.netbsd.org/pub/NetBSD-archive/'
                      'NetBSD-4.0/prep/installation/floppy/generic_com0.fs')
         drive_hash = 'dbcfc09912e71bd5f0d82c7c1ee43082fb596ceb'
         drive_path = self.fetch_asset(drive_url, asset_hash=drive_hash)
@@ -61,7 +60,6 @@ class IbmPrep40pMachine(Test):
         wait_for_console_pattern(self, '>> Memory: 192M')
         wait_for_console_pattern(self, '>> CPU type PowerPC,604')
 
-    @skipIf(os.getenv('CONTINUOUS_INTEGRATION'), 'Running on Travis-CI')
     def test_openbios_and_netbsd(self):
         """
         :avocado: tags=arch:ppc
diff --git a/tests/docker/dockerfiles/centos8.docker b/tests/docker/dockerfiles/centos8.docker
index 585dfad..a589142 100644
--- a/tests/docker/dockerfiles/centos8.docker
+++ b/tests/docker/dockerfiles/centos8.docker
@@ -18,6 +18,7 @@ ENV PACKAGES \
     lzo-devel \
     make \
     mesa-libEGL-devel \
+    nmap-ncat \
     nettle-devel \
     ninja-build \
     perl-Test-Harness \
diff --git a/tests/docker/dockerfiles/debian-amd64.docker b/tests/docker/dockerfiles/debian-amd64.docker
index 314c6ba..55075d9 100644
--- a/tests/docker/dockerfiles/debian-amd64.docker
+++ b/tests/docker/dockerfiles/debian-amd64.docker
@@ -23,6 +23,9 @@ RUN apt update && \
         libsnappy-dev \
         libvte-dev \
         netcat-openbsd \
+        openssh-client \
+        python3-numpy \
+        python3-opencv \
         python3-venv
 
 # virgl
diff --git a/tests/docker/dockerfiles/fedora.docker b/tests/docker/dockerfiles/fedora.docker
index ac79d95..0b5053f 100644
--- a/tests/docker/dockerfiles/fedora.docker
+++ b/tests/docker/dockerfiles/fedora.docker
@@ -73,6 +73,7 @@ ENV PACKAGES \
     mingw64-pixman \
     mingw64-pkg-config \
     mingw64-SDL2 \
+    nmap-ncat \
     ncurses-devel \
     nettle-devel \
     ninja-build \
diff --git a/tests/docker/dockerfiles/ubuntu2004.docker b/tests/docker/dockerfiles/ubuntu2004.docker
index 17b37cd..355bbb3 100644
--- a/tests/docker/dockerfiles/ubuntu2004.docker
+++ b/tests/docker/dockerfiles/ubuntu2004.docker
@@ -47,6 +47,7 @@ ENV PACKAGES flex bison \
     libxen-dev \
     libzstd-dev \
     make \
+    netcat-openbsd \
     ninja-build \
     python3-numpy \
     python3-opencv \
diff --git a/tests/qtest/fuzz/fuzz.c b/tests/qtest/fuzz/fuzz.c
index eb00704..7be7226 100644
--- a/tests/qtest/fuzz/fuzz.c
+++ b/tests/qtest/fuzz/fuzz.c
@@ -118,6 +118,19 @@ static FuzzTarget *fuzz_get_target(char* name)
 }
 
 
+/* Sometimes called by libfuzzer to mutate two inputs into one */
+size_t LLVMFuzzerCustomCrossOver(const uint8_t *data1, size_t size1,
+                                 const uint8_t *data2, size_t size2,
+                                 uint8_t *out, size_t max_out_size,
+                                 unsigned int seed)
+{
+    if (fuzz_target->crossover) {
+        return fuzz_target->crossover(data1, size1, data2, size2, out,
+                                      max_out_size, seed);
+    }
+    return 0;
+}
+
 /* Executed for each fuzzing-input */
 int LLVMFuzzerTestOneInput(const unsigned char *Data, size_t Size)
 {
diff --git a/tests/qtest/fuzz/fuzz.h b/tests/qtest/fuzz/fuzz.h
index 8eb765e..08e9560 100644
--- a/tests/qtest/fuzz/fuzz.h
+++ b/tests/qtest/fuzz/fuzz.h
@@ -77,6 +77,30 @@ typedef struct FuzzTarget {
      */
     void(*fuzz)(QTestState *, const unsigned char *, size_t);
 
+    /*
+     * The fuzzer can specify a "Custom Crossover" function for combining two
+     * inputs from the corpus. This function is sometimes called by libfuzzer
+     * when mutating inputs.
+     *
+     * data1: location of first input
+     * size1: length of first input
+     * data1: location of second input
+     * size1: length of second input
+     * out: where to place the resulting, mutated input
+     * max_out_size: the maximum length of the input that can be placed in out
+     * seed: the seed that should be used to make mutations deterministic, when
+     *       needed
+     *
+     * See libfuzzer's LLVMFuzzerCustomCrossOver API for more info.
+     *
+     * Can be NULL
+     */
+    size_t(*crossover)(const uint8_t *data1, size_t size1,
+                       const uint8_t *data2, size_t size2,
+                       uint8_t *out, size_t max_out_size,
+                       unsigned int seed);
+
+    void *opaque;
 } FuzzTarget;
 
 void flush_events(QTestState *);
@@ -91,6 +115,10 @@ void fuzz_qtest_set_serialize(bool option);
  */
 void fuzz_add_target(const FuzzTarget *target);
 
+size_t LLVMFuzzerCustomCrossOver(const uint8_t *data1, size_t size1,
+                                 const uint8_t *data2, size_t size2,
+                                 uint8_t *out, size_t max_out_size,
+                                 unsigned int seed);
 int LLVMFuzzerTestOneInput(const unsigned char *Data, size_t Size);
 int LLVMFuzzerInitialize(int *argc, char ***argv, char ***envp);
 
diff --git a/tests/qtest/fuzz/generic_fuzz.c b/tests/qtest/fuzz/generic_fuzz.c
new file mode 100644
index 0000000..a8f5864
--- /dev/null
+++ b/tests/qtest/fuzz/generic_fuzz.c
@@ -0,0 +1,954 @@
+/*
+ * Generic Virtual-Device Fuzzing Target
+ *
+ * Copyright Red Hat Inc., 2020
+ *
+ * Authors:
+ *  Alexander Bulekov   <alxndr@bu.edu>
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2 or later.
+ * See the COPYING file in the top-level directory.
+ */
+
+#include "qemu/osdep.h"
+
+#include <wordexp.h>
+
+#include "hw/core/cpu.h"
+#include "tests/qtest/libqos/libqtest.h"
+#include "fuzz.h"
+#include "fork_fuzz.h"
+#include "exec/address-spaces.h"
+#include "string.h"
+#include "exec/memory.h"
+#include "exec/ramblock.h"
+#include "exec/address-spaces.h"
+#include "hw/qdev-core.h"
+#include "hw/pci/pci.h"
+#include "hw/boards.h"
+#include "generic_fuzz_configs.h"
+
+/*
+ * SEPARATOR is used to separate "operations" in the fuzz input
+ */
+#define SEPARATOR "FUZZ"
+
+enum cmds {
+    OP_IN,
+    OP_OUT,
+    OP_READ,
+    OP_WRITE,
+    OP_PCI_READ,
+    OP_PCI_WRITE,
+    OP_DISABLE_PCI,
+    OP_ADD_DMA_PATTERN,
+    OP_CLEAR_DMA_PATTERNS,
+    OP_CLOCK_STEP,
+};
+
+#define DEFAULT_TIMEOUT_US 100000
+#define USEC_IN_SEC 1000000000
+
+#define MAX_DMA_FILL_SIZE 0x10000
+
+#define PCI_HOST_BRIDGE_CFG 0xcf8
+#define PCI_HOST_BRIDGE_DATA 0xcfc
+
+typedef struct {
+    ram_addr_t addr;
+    ram_addr_t size; /* The number of bytes until the end of the I/O region */
+} address_range;
+
+static useconds_t timeout = DEFAULT_TIMEOUT_US;
+
+static bool qtest_log_enabled;
+
+/*
+ * A pattern used to populate a DMA region or perform a memwrite. This is
+ * useful for e.g. populating tables of unique addresses.
+ * Example {.index = 1; .stride = 2; .len = 3; .data = "\x00\x01\x02"}
+ * Renders as: 00 01 02   00 03 02   00 05 02   00 07 02 ...
+ */
+typedef struct {
+    uint8_t index;      /* Index of a byte to increment by stride */
+    uint8_t stride;     /* Increment each index'th byte by this amount */
+    size_t len;
+    const uint8_t *data;
+} pattern;
+
+/* Avoid filling the same DMA region between MMIO/PIO commands ? */
+static bool avoid_double_fetches;
+
+static QTestState *qts_global; /* Need a global for the DMA callback */
+
+/*
+ * List of memory regions that are children of QOM objects specified by the
+ * user for fuzzing.
+ */
+static GHashTable *fuzzable_memoryregions;
+static GPtrArray *fuzzable_pci_devices;
+
+struct get_io_cb_info {
+    int index;
+    int found;
+    address_range result;
+};
+
+static int get_io_address_cb(Int128 start, Int128 size,
+                          const MemoryRegion *mr, void *opaque) {
+    struct get_io_cb_info *info = opaque;
+    if (g_hash_table_lookup(fuzzable_memoryregions, mr)) {
+        if (info->index == 0) {
+            info->result.addr = (ram_addr_t)start;
+            info->result.size = (ram_addr_t)size;
+            info->found = 1;
+            return 1;
+        }
+        info->index--;
+    }
+    return 0;
+}
+
+/*
+ * List of dma regions populated since the last fuzzing command. Used to ensure
+ * that we only write to each DMA address once, to avoid race conditions when
+ * building reproducers.
+ */
+static GArray *dma_regions;
+
+static GArray *dma_patterns;
+static int dma_pattern_index;
+static bool pci_disabled;
+
+/*
+ * Allocate a block of memory and populate it with a pattern.
+ */
+static void *pattern_alloc(pattern p, size_t len)
+{
+    int i;
+    uint8_t *buf = g_malloc(len);
+    uint8_t sum = 0;
+
+    for (i = 0; i < len; ++i) {
+        buf[i] = p.data[i % p.len];
+        if ((i % p.len) == p.index) {
+            buf[i] += sum;
+            sum += p.stride;
+        }
+    }
+    return buf;
+}
+
+static int memory_access_size(MemoryRegion *mr, unsigned l, hwaddr addr)
+{
+    unsigned access_size_max = mr->ops->valid.max_access_size;
+
+    /*
+     * Regions are assumed to support 1-4 byte accesses unless
+     * otherwise specified.
+     */
+    if (access_size_max == 0) {
+        access_size_max = 4;
+    }
+
+    /* Bound the maximum access by the alignment of the address.  */
+    if (!mr->ops->impl.unaligned) {
+        unsigned align_size_max = addr & -addr;
+        if (align_size_max != 0 && align_size_max < access_size_max) {
+            access_size_max = align_size_max;
+        }
+    }
+
+    /* Don't attempt accesses larger than the maximum.  */
+    if (l > access_size_max) {
+        l = access_size_max;
+    }
+    l = pow2floor(l);
+
+    return l;
+}
+
+/*
+ * Call-back for functions that perform DMA reads from guest memory. Confirm
+ * that the region has not already been populated since the last loop in
+ * generic_fuzz(), avoiding potential race-conditions, which we don't have
+ * a good way for reproducing right now.
+ */
+void fuzz_dma_read_cb(size_t addr, size_t len, MemoryRegion *mr, bool is_write)
+{
+    /* Are we in the generic-fuzzer or are we using another fuzz-target? */
+    if (!qts_global) {
+        return;
+    }
+
+    /*
+     * Return immediately if:
+     * - We have no DMA patterns defined
+     * - The length of the DMA read request is zero
+     * - The DMA read is hitting an MR other than the machine's main RAM
+     * - The DMA request is not a read (what happens for a address_space_map
+     *   with is_write=True? Can the device use the same pointer to do reads?)
+     * - The DMA request hits past the bounds of our RAM
+     */
+    if (dma_patterns->len == 0
+        || len == 0
+        /* || mr != MACHINE(qdev_get_machine())->ram */
+        || is_write
+        || addr > current_machine->ram_size) {
+        return;
+    }
+
+    /*
+     * If we overlap with any existing dma_regions, split the range and only
+     * populate the non-overlapping parts.
+     */
+    address_range region;
+    bool double_fetch = false;
+    for (int i = 0;
+         i < dma_regions->len && (avoid_double_fetches || qtest_log_enabled);
+         ++i) {
+        region = g_array_index(dma_regions, address_range, i);
+        if (addr < region.addr + region.size && addr + len > region.addr) {
+            double_fetch = true;
+            if (addr < region.addr
+                && avoid_double_fetches) {
+                fuzz_dma_read_cb(addr, region.addr - addr, mr, is_write);
+            }
+            if (addr + len > region.addr + region.size
+                && avoid_double_fetches) {
+                fuzz_dma_read_cb(region.addr + region.size,
+                        addr + len - (region.addr + region.size), mr, is_write);
+            }
+            return;
+        }
+    }
+
+    /* Cap the length of the DMA access to something reasonable */
+    len = MIN(len, MAX_DMA_FILL_SIZE);
+
+    address_range ar = {addr, len};
+    g_array_append_val(dma_regions, ar);
+    pattern p = g_array_index(dma_patterns, pattern, dma_pattern_index);
+    void *buf = pattern_alloc(p, ar.size);
+    hwaddr l, addr1;
+    MemoryRegion *mr1;
+    uint8_t *ram_ptr;
+    while (len > 0) {
+        l = len;
+        mr1 = address_space_translate(first_cpu->as,
+                                      addr, &addr1, &l, true,
+                                      MEMTXATTRS_UNSPECIFIED);
+
+        if (!(memory_region_is_ram(mr1) ||
+              memory_region_is_romd(mr1))) {
+            l = memory_access_size(mr1, l, addr1);
+        } else {
+            /* ROM/RAM case */
+            ram_ptr = qemu_map_ram_ptr(mr1->ram_block, addr1);
+            memcpy(ram_ptr, buf, l);
+            break;
+        }
+        len -= l;
+        buf += l;
+        addr += l;
+
+    }
+    if (qtest_log_enabled) {
+        /*
+         * With QTEST_LOG, use a normal, slow QTest memwrite. Prefix the log
+         * that will be written by qtest.c with a DMA tag, so we can reorder
+         * the resulting QTest trace so the DMA fills precede the last PIO/MMIO
+         * command.
+         */
+        fprintf(stderr, "[DMA] ");
+        if (double_fetch) {
+            fprintf(stderr, "[DOUBLE-FETCH] ");
+        }
+        fflush(stderr);
+    }
+    qtest_memwrite(qts_global, ar.addr, buf, ar.size);
+    g_free(buf);
+
+    /* Increment the index of the pattern for the next DMA access */
+    dma_pattern_index = (dma_pattern_index + 1) % dma_patterns->len;
+}
+
+/*
+ * Here we want to convert a fuzzer-provided [io-region-index, offset] to
+ * a physical address. To do this, we iterate over all of the matched
+ * MemoryRegions. Check whether each region exists within the particular io
+ * space. Return the absolute address of the offset within the index'th region
+ * that is a subregion of the io_space and the distance until the end of the
+ * memory region.
+ */
+static bool get_io_address(address_range *result, AddressSpace *as,
+                            uint8_t index,
+                            uint32_t offset) {
+    FlatView *view;
+    view = as->current_map;
+    g_assert(view);
+    struct get_io_cb_info cb_info = {};
+
+    cb_info.index = index;
+
+    /*
+     * Loop around the FlatView until we match "index" number of
+     * fuzzable_memoryregions, or until we know that there are no matching
+     * memory_regions.
+     */
+    do {
+        flatview_for_each_range(view, get_io_address_cb , &cb_info);
+    } while (cb_info.index != index && !cb_info.found);
+
+    *result = cb_info.result;
+    return cb_info.found;
+}
+
+static bool get_pio_address(address_range *result,
+                            uint8_t index, uint16_t offset)
+{
+    /*
+     * PIO BARs can be set past the maximum port address (0xFFFF). Thus, result
+     * can contain an addr that extends past the PIO space. When we pass this
+     * address to qtest_in/qtest_out, it is cast to a uint16_t, so we might end
+     * up fuzzing a completely different MemoryRegion/Device. Therefore, check
+     * that the address here is within the PIO space limits.
+     */
+    bool found = get_io_address(result, &address_space_io, index, offset);
+    return result->addr <= 0xFFFF ? found : false;
+}
+
+static bool get_mmio_address(address_range *result,
+                             uint8_t index, uint32_t offset)
+{
+    return get_io_address(result, &address_space_memory, index, offset);
+}
+
+static void op_in(QTestState *s, const unsigned char * data, size_t len)
+{
+    enum Sizes {Byte, Word, Long, end_sizes};
+    struct {
+        uint8_t size;
+        uint8_t base;
+        uint16_t offset;
+    } a;
+    address_range abs;
+
+    if (len < sizeof(a)) {
+        return;
+    }
+    memcpy(&a, data, sizeof(a));
+    if (get_pio_address(&abs, a.base, a.offset) == 0) {
+        return;
+    }
+
+    switch (a.size %= end_sizes) {
+    case Byte:
+        qtest_inb(s, abs.addr);
+        break;
+    case Word:
+        if (abs.size >= 2) {
+            qtest_inw(s, abs.addr);
+        }
+        break;
+    case Long:
+        if (abs.size >= 4) {
+            qtest_inl(s, abs.addr);
+        }
+        break;
+    }
+}
+
+static void op_out(QTestState *s, const unsigned char * data, size_t len)
+{
+    enum Sizes {Byte, Word, Long, end_sizes};
+    struct {
+        uint8_t size;
+        uint8_t base;
+        uint16_t offset;
+        uint32_t value;
+    } a;
+    address_range abs;
+
+    if (len < sizeof(a)) {
+        return;
+    }
+    memcpy(&a, data, sizeof(a));
+
+    if (get_pio_address(&abs, a.base, a.offset) == 0) {
+        return;
+    }
+
+    switch (a.size %= end_sizes) {
+    case Byte:
+        qtest_outb(s, abs.addr, a.value & 0xFF);
+        break;
+    case Word:
+        if (abs.size >= 2) {
+            qtest_outw(s, abs.addr, a.value & 0xFFFF);
+        }
+        break;
+    case Long:
+        if (abs.size >= 4) {
+            qtest_outl(s, abs.addr, a.value);
+        }
+        break;
+    }
+}
+
+static void op_read(QTestState *s, const unsigned char * data, size_t len)
+{
+    enum Sizes {Byte, Word, Long, Quad, end_sizes};
+    struct {
+        uint8_t size;
+        uint8_t base;
+        uint32_t offset;
+    } a;
+    address_range abs;
+
+    if (len < sizeof(a)) {
+        return;
+    }
+    memcpy(&a, data, sizeof(a));
+
+    if (get_mmio_address(&abs, a.base, a.offset) == 0) {
+        return;
+    }
+
+    switch (a.size %= end_sizes) {
+    case Byte:
+        qtest_readb(s, abs.addr);
+        break;
+    case Word:
+        if (abs.size >= 2) {
+            qtest_readw(s, abs.addr);
+        }
+        break;
+    case Long:
+        if (abs.size >= 4) {
+            qtest_readl(s, abs.addr);
+        }
+        break;
+    case Quad:
+        if (abs.size >= 8) {
+            qtest_readq(s, abs.addr);
+        }
+        break;
+    }
+}
+
+static void op_write(QTestState *s, const unsigned char * data, size_t len)
+{
+    enum Sizes {Byte, Word, Long, Quad, end_sizes};
+    struct {
+        uint8_t size;
+        uint8_t base;
+        uint32_t offset;
+        uint64_t value;
+    } a;
+    address_range abs;
+
+    if (len < sizeof(a)) {
+        return;
+    }
+    memcpy(&a, data, sizeof(a));
+
+    if (get_mmio_address(&abs, a.base, a.offset) == 0) {
+        return;
+    }
+
+    switch (a.size %= end_sizes) {
+    case Byte:
+            qtest_writeb(s, abs.addr, a.value & 0xFF);
+        break;
+    case Word:
+        if (abs.size >= 2) {
+            qtest_writew(s, abs.addr, a.value & 0xFFFF);
+        }
+        break;
+    case Long:
+        if (abs.size >= 4) {
+            qtest_writel(s, abs.addr, a.value & 0xFFFFFFFF);
+        }
+        break;
+    case Quad:
+        if (abs.size >= 8) {
+            qtest_writeq(s, abs.addr, a.value);
+        }
+        break;
+    }
+}
+
+static void op_pci_read(QTestState *s, const unsigned char * data, size_t len)
+{
+    enum Sizes {Byte, Word, Long, end_sizes};
+    struct {
+        uint8_t size;
+        uint8_t base;
+        uint8_t offset;
+    } a;
+    if (len < sizeof(a) || fuzzable_pci_devices->len == 0 || pci_disabled) {
+        return;
+    }
+    memcpy(&a, data, sizeof(a));
+    PCIDevice *dev = g_ptr_array_index(fuzzable_pci_devices,
+                                  a.base % fuzzable_pci_devices->len);
+    int devfn = dev->devfn;
+    qtest_outl(s, PCI_HOST_BRIDGE_CFG, (1U << 31) | (devfn << 8) | a.offset);
+    switch (a.size %= end_sizes) {
+    case Byte:
+        qtest_inb(s, PCI_HOST_BRIDGE_DATA);
+        break;
+    case Word:
+        qtest_inw(s, PCI_HOST_BRIDGE_DATA);
+        break;
+    case Long:
+        qtest_inl(s, PCI_HOST_BRIDGE_DATA);
+        break;
+    }
+}
+
+static void op_pci_write(QTestState *s, const unsigned char * data, size_t len)
+{
+    enum Sizes {Byte, Word, Long, end_sizes};
+    struct {
+        uint8_t size;
+        uint8_t base;
+        uint8_t offset;
+        uint32_t value;
+    } a;
+    if (len < sizeof(a) || fuzzable_pci_devices->len == 0 || pci_disabled) {
+        return;
+    }
+    memcpy(&a, data, sizeof(a));
+    PCIDevice *dev = g_ptr_array_index(fuzzable_pci_devices,
+                                  a.base % fuzzable_pci_devices->len);
+    int devfn = dev->devfn;
+    qtest_outl(s, PCI_HOST_BRIDGE_CFG, (1U << 31) | (devfn << 8) | a.offset);
+    switch (a.size %= end_sizes) {
+    case Byte:
+        qtest_outb(s, PCI_HOST_BRIDGE_DATA, a.value & 0xFF);
+        break;
+    case Word:
+        qtest_outw(s, PCI_HOST_BRIDGE_DATA, a.value & 0xFFFF);
+        break;
+    case Long:
+        qtest_outl(s, PCI_HOST_BRIDGE_DATA, a.value & 0xFFFFFFFF);
+        break;
+    }
+}
+
+static void op_add_dma_pattern(QTestState *s,
+                               const unsigned char *data, size_t len)
+{
+    struct {
+        /*
+         * index and stride can be used to increment the index-th byte of the
+         * pattern by the value stride, for each loop of the pattern.
+         */
+        uint8_t index;
+        uint8_t stride;
+    } a;
+
+    if (len < sizeof(a) + 1) {
+        return;
+    }
+    memcpy(&a, data, sizeof(a));
+    pattern p = {a.index, a.stride, len - sizeof(a), data + sizeof(a)};
+    p.index = a.index % p.len;
+    g_array_append_val(dma_patterns, p);
+    return;
+}
+
+static void op_clear_dma_patterns(QTestState *s,
+                                  const unsigned char *data, size_t len)
+{
+    g_array_set_size(dma_patterns, 0);
+    dma_pattern_index = 0;
+}
+
+static void op_clock_step(QTestState *s, const unsigned char *data, size_t len)
+{
+    qtest_clock_step_next(s);
+}
+
+static void op_disable_pci(QTestState *s, const unsigned char *data, size_t len)
+{
+    pci_disabled = true;
+}
+
+static void handle_timeout(int sig)
+{
+    if (qtest_log_enabled) {
+        fprintf(stderr, "[Timeout]\n");
+        fflush(stderr);
+    }
+    _Exit(0);
+}
+
+/*
+ * Here, we interpret random bytes from the fuzzer, as a sequence of commands.
+ * Some commands can be variable-width, so we use a separator, SEPARATOR, to
+ * specify the boundaries between commands. SEPARATOR is used to separate
+ * "operations" in the fuzz input. Why use a separator, instead of just using
+ * the operations' length to identify operation boundaries?
+ *   1. This is a simple way to support variable-length operations
+ *   2. This adds "stability" to the input.
+ *      For example take the input "AbBcgDefg", where there is no separator and
+ *      Opcodes are capitalized.
+ *      Simply, by removing the first byte, we end up with a very different
+ *      sequence:
+ *      BbcGdefg...
+ *      By adding a separator, we avoid this problem:
+ *      Ab SEP Bcg SEP Defg -> B SEP Bcg SEP Defg
+ *      Since B uses two additional bytes as operands, the first "B" will be
+ *      ignored. The fuzzer actively tries to reduce inputs, so such unused
+ *      bytes are likely to be pruned, eventually.
+ *
+ *  SEPARATOR is trivial for the fuzzer to discover when using ASan. Optionally,
+ *  SEPARATOR can be manually specified as a dictionary value (see libfuzzer's
+ *  -dict), though this should not be necessary.
+ *
+ * As a result, the stream of bytes is converted into a sequence of commands.
+ * In a simplified example where SEPARATOR is 0xFF:
+ * 00 01 02 FF 03 04 05 06 FF 01 FF ...
+ * becomes this sequence of commands:
+ * 00 01 02    -> op00 (0102)   -> in (0102, 2)
+ * 03 04 05 06 -> op03 (040506) -> write (040506, 3)
+ * 01          -> op01 (-,0)    -> out (-,0)
+ * ...
+ *
+ * Note here that it is the job of the individual opcode functions to check
+ * that enough data was provided. I.e. in the last command out (,0), out needs
+ * to check that there is not enough data provided to select an address/value
+ * for the operation.
+ */
+static void generic_fuzz(QTestState *s, const unsigned char *Data, size_t Size)
+{
+    void (*ops[]) (QTestState *s, const unsigned char* , size_t) = {
+        [OP_IN]                 = op_in,
+        [OP_OUT]                = op_out,
+        [OP_READ]               = op_read,
+        [OP_WRITE]              = op_write,
+        [OP_PCI_READ]           = op_pci_read,
+        [OP_PCI_WRITE]          = op_pci_write,
+        [OP_DISABLE_PCI]        = op_disable_pci,
+        [OP_ADD_DMA_PATTERN]    = op_add_dma_pattern,
+        [OP_CLEAR_DMA_PATTERNS] = op_clear_dma_patterns,
+        [OP_CLOCK_STEP]         = op_clock_step,
+    };
+    const unsigned char *cmd = Data;
+    const unsigned char *nextcmd;
+    size_t cmd_len;
+    uint8_t op;
+
+    if (fork() == 0) {
+        /*
+         * Sometimes the fuzzer will find inputs that take quite a long time to
+         * process. Often times, these inputs do not result in new coverage.
+         * Even if these inputs might be interesting, they can slow down the
+         * fuzzer, overall. Set a timeout to avoid hurting performance, too much
+         */
+        if (timeout) {
+            struct sigaction sact;
+            struct itimerval timer;
+
+            sigemptyset(&sact.sa_mask);
+            sact.sa_flags   = SA_NODEFER;
+            sact.sa_handler = handle_timeout;
+            sigaction(SIGALRM, &sact, NULL);
+
+            memset(&timer, 0, sizeof(timer));
+            timer.it_value.tv_sec = timeout / USEC_IN_SEC;
+            timer.it_value.tv_usec = timeout % USEC_IN_SEC;
+            setitimer(ITIMER_VIRTUAL, &timer, NULL);
+        }
+
+        op_clear_dma_patterns(s, NULL, 0);
+        pci_disabled = false;
+
+        while (cmd && Size) {
+            /* Get the length until the next command or end of input */
+            nextcmd = memmem(cmd, Size, SEPARATOR, strlen(SEPARATOR));
+            cmd_len = nextcmd ? nextcmd - cmd : Size;
+
+            if (cmd_len > 0) {
+                /* Interpret the first byte of the command as an opcode */
+                op = *cmd % (sizeof(ops) / sizeof((ops)[0]));
+                ops[op](s, cmd + 1, cmd_len - 1);
+
+                /* Run the main loop */
+                flush_events(s);
+            }
+            /* Advance to the next command */
+            cmd = nextcmd ? nextcmd + sizeof(SEPARATOR) - 1 : nextcmd;
+            Size = Size - (cmd_len + sizeof(SEPARATOR) - 1);
+            g_array_set_size(dma_regions, 0);
+        }
+        _Exit(0);
+    } else {
+        flush_events(s);
+        wait(0);
+    }
+}
+
+static void usage(void)
+{
+    printf("Please specify the following environment variables:\n");
+    printf("QEMU_FUZZ_ARGS= the command line arguments passed to qemu\n");
+    printf("QEMU_FUZZ_OBJECTS= "
+            "a space separated list of QOM type names for objects to fuzz\n");
+    printf("Optionally: QEMU_AVOID_DOUBLE_FETCH= "
+            "Try to avoid racy DMA double fetch bugs? %d by default\n",
+            avoid_double_fetches);
+    printf("Optionally: QEMU_FUZZ_TIMEOUT= Specify a custom timeout (us). "
+            "0 to disable. %d by default\n", timeout);
+    exit(0);
+}
+
+static int locate_fuzz_memory_regions(Object *child, void *opaque)
+{
+    const char *name;
+    MemoryRegion *mr;
+    if (object_dynamic_cast(child, TYPE_MEMORY_REGION)) {
+        mr = MEMORY_REGION(child);
+        if ((memory_region_is_ram(mr) ||
+            memory_region_is_ram_device(mr) ||
+            memory_region_is_rom(mr)) == false) {
+            name = object_get_canonical_path_component(child);
+            /*
+             * We don't want duplicate pointers to the same MemoryRegion, so
+             * try to remove copies of the pointer, before adding it.
+             */
+            g_hash_table_insert(fuzzable_memoryregions, mr, (gpointer)true);
+        }
+    }
+    return 0;
+}
+
+static int locate_fuzz_objects(Object *child, void *opaque)
+{
+    char *pattern = opaque;
+    if (g_pattern_match_simple(pattern, object_get_typename(child))) {
+        /* Find and save ptrs to any child MemoryRegions */
+        object_child_foreach_recursive(child, locate_fuzz_memory_regions, NULL);
+
+        /*
+         * We matched an object. If its a PCI device, store a pointer to it so
+         * we can map BARs and fuzz its config space.
+         */
+        if (object_dynamic_cast(OBJECT(child), TYPE_PCI_DEVICE)) {
+            /*
+             * Don't want duplicate pointers to the same PCIDevice, so remove
+             * copies of the pointer, before adding it.
+             */
+            g_ptr_array_remove_fast(fuzzable_pci_devices, PCI_DEVICE(child));
+            g_ptr_array_add(fuzzable_pci_devices, PCI_DEVICE(child));
+        }
+    } else if (object_dynamic_cast(OBJECT(child), TYPE_MEMORY_REGION)) {
+        if (g_pattern_match_simple(pattern,
+            object_get_canonical_path_component(child))) {
+            MemoryRegion *mr;
+            mr = MEMORY_REGION(child);
+            if ((memory_region_is_ram(mr) ||
+                 memory_region_is_ram_device(mr) ||
+                 memory_region_is_rom(mr)) == false) {
+                g_hash_table_insert(fuzzable_memoryregions, mr, (gpointer)true);
+            }
+        }
+    }
+    return 0;
+}
+
+static void generic_pre_fuzz(QTestState *s)
+{
+    GHashTableIter iter;
+    MemoryRegion *mr;
+    char **result;
+
+    if (!getenv("QEMU_FUZZ_OBJECTS")) {
+        usage();
+    }
+    if (getenv("QTEST_LOG")) {
+        qtest_log_enabled = 1;
+    }
+    if (getenv("QEMU_AVOID_DOUBLE_FETCH")) {
+        avoid_double_fetches = 1;
+    }
+    if (getenv("QEMU_FUZZ_TIMEOUT")) {
+        timeout = g_ascii_strtoll(getenv("QEMU_FUZZ_TIMEOUT"), NULL, 0);
+    }
+    qts_global = s;
+
+    dma_regions = g_array_new(false, false, sizeof(address_range));
+    dma_patterns = g_array_new(false, false, sizeof(pattern));
+
+    fuzzable_memoryregions = g_hash_table_new(NULL, NULL);
+    fuzzable_pci_devices   = g_ptr_array_new();
+
+    result = g_strsplit(getenv("QEMU_FUZZ_OBJECTS"), " ", -1);
+    for (int i = 0; result[i] != NULL; i++) {
+        printf("Matching objects by name %s\n", result[i]);
+        object_child_foreach_recursive(qdev_get_machine(),
+                                    locate_fuzz_objects,
+                                    result[i]);
+    }
+    g_strfreev(result);
+    printf("This process will try to fuzz the following MemoryRegions:\n");
+
+    g_hash_table_iter_init(&iter, fuzzable_memoryregions);
+    while (g_hash_table_iter_next(&iter, (gpointer)&mr, NULL)) {
+        printf("  * %s (size %lx)\n",
+               object_get_canonical_path_component(&(mr->parent_obj)),
+               (uint64_t)mr->size);
+    }
+
+    if (!g_hash_table_size(fuzzable_memoryregions)) {
+        printf("No fuzzable memory regions found...\n");
+        exit(1);
+    }
+
+    counter_shm_init();
+}
+
+/*
+ * When libfuzzer gives us two inputs to combine, return a new input with the
+ * following structure:
+ *
+ * Input 1 (data1)
+ * SEPARATOR
+ * Clear out the DMA Patterns
+ * SEPARATOR
+ * Disable the pci_read/write instructions
+ * SEPARATOR
+ * Input 2 (data2)
+ *
+ * The idea is to collate the core behaviors of the two inputs.
+ * For example:
+ * Input 1: maps a device's BARs, sets up three DMA patterns, and triggers
+ *          device functionality A
+ * Input 2: maps a device's BARs, sets up one DMA pattern, and triggers device
+ *          functionality B
+ *
+ * This function attempts to produce an input that:
+ * Ouptut: maps a device's BARs, set up three DMA patterns, triggers
+ *          functionality A device, replaces the DMA patterns with a single
+ *          patten, and triggers device functionality B.
+ */
+static size_t generic_fuzz_crossover(const uint8_t *data1, size_t size1, const
+                                     uint8_t *data2, size_t size2, uint8_t *out,
+                                     size_t max_out_size, unsigned int seed)
+{
+    size_t copy_len = 0, size = 0;
+
+    /* Check that we have enough space for data1 and at least part of data2 */
+    if (max_out_size <= size1 + strlen(SEPARATOR) * 3 + 2) {
+        return 0;
+    }
+
+    /* Copy_Len in the first input */
+    copy_len = size1;
+    memcpy(out + size, data1, copy_len);
+    size += copy_len;
+    max_out_size -= copy_len;
+
+    /* Append a separator */
+    copy_len = strlen(SEPARATOR);
+    memcpy(out + size, SEPARATOR, copy_len);
+    size += copy_len;
+    max_out_size -= copy_len;
+
+    /* Clear out the DMA Patterns */
+    copy_len = 1;
+    if (copy_len) {
+        out[size] = OP_CLEAR_DMA_PATTERNS;
+    }
+    size += copy_len;
+    max_out_size -= copy_len;
+
+    /* Append a separator */
+    copy_len = strlen(SEPARATOR);
+    memcpy(out + size, SEPARATOR, copy_len);
+    size += copy_len;
+    max_out_size -= copy_len;
+
+    /* Disable PCI ops. Assume data1 took care of setting up PCI */
+    copy_len = 1;
+    if (copy_len) {
+        out[size] = OP_DISABLE_PCI;
+    }
+    size += copy_len;
+    max_out_size -= copy_len;
+
+    /* Append a separator */
+    copy_len = strlen(SEPARATOR);
+    memcpy(out + size, SEPARATOR, copy_len);
+    size += copy_len;
+    max_out_size -= copy_len;
+
+    /* Copy_Len over the second input */
+    copy_len = MIN(size2, max_out_size);
+    memcpy(out + size, data2, copy_len);
+    size += copy_len;
+    max_out_size -= copy_len;
+
+    return  size;
+}
+
+
+static GString *generic_fuzz_cmdline(FuzzTarget *t)
+{
+    GString *cmd_line = g_string_new(TARGET_NAME);
+    if (!getenv("QEMU_FUZZ_ARGS")) {
+        usage();
+    }
+    g_string_append_printf(cmd_line, " -display none \
+                                      -machine accel=qtest, \
+                                      -m 512M %s ", getenv("QEMU_FUZZ_ARGS"));
+    return cmd_line;
+}
+
+static GString *generic_fuzz_predefined_config_cmdline(FuzzTarget *t)
+{
+    const generic_fuzz_config *config;
+    g_assert(t->opaque);
+
+    config = t->opaque;
+    setenv("QEMU_FUZZ_ARGS", config->args, 1);
+    setenv("QEMU_FUZZ_OBJECTS", config->objects, 1);
+    return generic_fuzz_cmdline(t);
+}
+
+static void register_generic_fuzz_targets(void)
+{
+    fuzz_add_target(&(FuzzTarget){
+            .name = "generic-fuzz",
+            .description = "Fuzz based on any qemu command-line args. ",
+            .get_init_cmdline = generic_fuzz_cmdline,
+            .pre_fuzz = generic_pre_fuzz,
+            .fuzz = generic_fuzz,
+            .crossover = generic_fuzz_crossover
+    });
+
+    GString *name;
+    const generic_fuzz_config *config;
+
+    for (int i = 0;
+         i < sizeof(predefined_configs) / sizeof(generic_fuzz_config);
+         i++) {
+        config = predefined_configs + i;
+        name = g_string_new("generic-fuzz");
+        g_string_append_printf(name, "-%s", config->name);
+        fuzz_add_target(&(FuzzTarget){
+                .name = name->str,
+                .description = "Predefined generic-fuzz config.",
+                .get_init_cmdline = generic_fuzz_predefined_config_cmdline,
+                .pre_fuzz = generic_pre_fuzz,
+                .fuzz = generic_fuzz,
+                .crossover = generic_fuzz_crossover,
+                .opaque = (void *)config
+        });
+    }
+}
+
+fuzz_target_init(register_generic_fuzz_targets);
diff --git a/tests/qtest/fuzz/generic_fuzz_configs.h b/tests/qtest/fuzz/generic_fuzz_configs.h
new file mode 100644
index 0000000..c4d925f
--- /dev/null
+++ b/tests/qtest/fuzz/generic_fuzz_configs.h
@@ -0,0 +1,121 @@
+/*
+ * Generic Virtual-Device Fuzzing Target Configs
+ *
+ * Copyright Red Hat Inc., 2020
+ *
+ * Authors:
+ *  Alexander Bulekov   <alxndr@bu.edu>
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2 or later.
+ * See the COPYING file in the top-level directory.
+ */
+
+#ifndef GENERIC_FUZZ_CONFIGS_H
+#define GENERIC_FUZZ_CONFIGS_H
+
+#include "qemu/osdep.h"
+
+typedef struct generic_fuzz_config {
+    const char *name, *args, *objects;
+} generic_fuzz_config;
+
+const generic_fuzz_config predefined_configs[] = {
+    {
+        .name = "virtio-net-pci-slirp",
+        .args = "-M q35 -nodefaults "
+        "-device virtio-net,netdev=net0 -netdev user,id=net0",
+        .objects = "virtio*",
+    },{
+        .name = "virtio-blk",
+        .args = "-machine q35 -device virtio-blk,drive=disk0 "
+        "-drive file=null-co://,id=disk0,if=none,format=raw",
+        .objects = "virtio*",
+    },{
+        .name = "virtio-scsi",
+        .args = "-machine q35 -device virtio-scsi,num_queues=8 "
+        "-device scsi-hd,drive=disk0 "
+        "-drive file=null-co://,id=disk0,if=none,format=raw",
+        .objects = "scsi* virtio*",
+    },{
+        .name = "virtio-gpu",
+        .args = "-machine q35 -nodefaults -device virtio-gpu",
+        .objects = "virtio*",
+    },{
+        .name = "virtio-vga",
+        .args = "-machine q35 -nodefaults -device virtio-vga",
+        .objects = "virtio*",
+    },{
+        .name = "virtio-rng",
+        .args = "-machine q35 -nodefaults -device virtio-rng",
+        .objects = "virtio*",
+    },{
+        .name = "virtio-balloon",
+        .args = "-machine q35 -nodefaults -device virtio-balloon",
+        .objects = "virtio*",
+    },{
+        .name = "virtio-serial",
+        .args = "-machine q35 -nodefaults -device virtio-serial",
+        .objects = "virtio*",
+    },{
+        .name = "virtio-mouse",
+        .args = "-machine q35 -nodefaults -device virtio-mouse",
+        .objects = "virtio*",
+    },{
+        .name = "e1000",
+        .args = "-M q35 -nodefaults "
+        "-device e1000,netdev=net0 -netdev user,id=net0",
+        .objects = "e1000",
+    },{
+        .name = "e1000e",
+        .args = "-M q35 -nodefaults "
+        "-device e1000e,netdev=net0 -netdev user,id=net0",
+        .objects = "e1000e",
+    },{
+        .name = "cirrus-vga",
+        .args = "-machine q35 -nodefaults -device cirrus-vga",
+        .objects = "cirrus*",
+    },{
+        .name = "bochs-display",
+        .args = "-machine q35 -nodefaults -device bochs-display",
+        .objects = "bochs*",
+    },{
+        .name = "intel-hda",
+        .args = "-machine q35 -nodefaults -device intel-hda,id=hda0 "
+        "-device hda-output,bus=hda0.0 -device hda-micro,bus=hda0.0 "
+        "-device hda-duplex,bus=hda0.0",
+        .objects = "intel-hda",
+    },{
+        .name = "ide-hd",
+        .args = "-machine q35 -nodefaults "
+        "-drive file=null-co://,if=none,format=raw,id=disk0 "
+        "-device ide-hd,drive=disk0",
+        .objects = "ahci*",
+    },{
+        .name = "floppy",
+        .args = "-machine pc -nodefaults -device floppy,id=floppy0 "
+        "-drive id=disk0,file=null-co://,file.read-zeroes=on,if=none "
+        "-device floppy,drive=disk0,drive-type=288",
+        .objects = "fd* floppy*",
+    },{
+        .name = "xhci",
+        .args = "-machine q35 -nodefaults "
+        "-drive file=null-co://,if=none,format=raw,id=disk0 "
+        "-device qemu-xhci,id=xhci -device usb-tablet,bus=xhci.0 "
+        "-device usb-bot -device usb-storage,drive=disk0 "
+        "-chardev null,id=cd0 -chardev null,id=cd1 "
+        "-device usb-braille,chardev=cd0 -device usb-ccid -device usb-ccid "
+        "-device usb-kbd -device usb-mouse -device usb-serial,chardev=cd1 "
+        "-device usb-tablet -device usb-wacom-tablet -device usb-audio",
+        .objects = "*usb* *uhci* *xhci*",
+    },{
+        .name = "pc-i440fx",
+        .args = "-machine pc",
+        .objects = "*",
+    },{
+        .name = "pc-q35",
+        .args = "-machine q35",
+        .objects = "*",
+    }
+};
+
+#endif
diff --git a/tests/qtest/fuzz/meson.build b/tests/qtest/fuzz/meson.build
index b31ace7..5162321 100644
--- a/tests/qtest/fuzz/meson.build
+++ b/tests/qtest/fuzz/meson.build
@@ -5,6 +5,7 @@ specific_fuzz_ss.add(files('fuzz.c', 'fork_fuzz.c', 'qos_fuzz.c',
 specific_fuzz_ss.add(when: 'CONFIG_I440FX', if_true: files('i440fx_fuzz.c'))
 specific_fuzz_ss.add(when: 'CONFIG_VIRTIO_NET', if_true: files('virtio_net_fuzz.c'))
 specific_fuzz_ss.add(when: 'CONFIG_VIRTIO_SCSI', if_true: files('virtio_scsi_fuzz.c'))
+specific_fuzz_ss.add(files('generic_fuzz.c'))
 
 fork_fuzz = declare_dependency(
   link_args: config_host['FUZZ_EXE_LDFLAGS'].split() +
diff --git a/tests/qtest/libqtest.c b/tests/qtest/libqtest.c
index 08929f5..99deff4 100644
--- a/tests/qtest/libqtest.c
+++ b/tests/qtest/libqtest.c
@@ -621,7 +621,7 @@ QDict *qtest_qmp_receive(QTestState *s)
             return response;
         }
         /* Stash the event for a later consumption */
-        s->pending_events = g_list_prepend(s->pending_events, response);
+        s->pending_events = g_list_append(s->pending_events, response);
     }
 }
 
@@ -795,15 +795,12 @@ void qtest_qmp_send_raw(QTestState *s, const char *fmt, ...)
 
 QDict *qtest_qmp_event_ref(QTestState *s, const char *event)
 {
-    GList *next = NULL;
-    QDict *response;
-
-    for (GList *it = s->pending_events; it != NULL; it = next) {
+    while (s->pending_events) {
 
-        next = it->next;
-        response = (QDict *)it->data;
+        GList *first = s->pending_events;
+        QDict *response = (QDict *)first->data;
 
-        s->pending_events = g_list_remove_link(s->pending_events, it);
+        s->pending_events = g_list_delete_link(s->pending_events, first);
 
         if (!strcmp(qdict_get_str(response, "event"), event)) {
             return response;
@@ -870,9 +867,14 @@ char *qtest_hmp(QTestState *s, const char *fmt, ...)
 const char *qtest_get_arch(void)
 {
     const char *qemu = qtest_qemu_binary();
-    const char *end = strrchr(qemu, '/');
+    const char *end = strrchr(qemu, '-');
+
+    if (!end) {
+        fprintf(stderr, "Can't determine architecture from binary name.\n");
+        abort();
+    }
 
-    return end + strlen("/qemu-system-");
+    return end + 1;
 }
 
 bool qtest_get_irq(QTestState *s, int num)
diff --git a/tests/qtest/meson.build b/tests/qtest/meson.build
index 28d4068..7e0ecaa 100644
--- a/tests/qtest/meson.build
+++ b/tests/qtest/meson.build
@@ -133,12 +133,13 @@ qtests_sparc64 = \
   (config_all_devices.has_key('CONFIG_ISA_TESTDEV') ? ['endianness-test'] : []) +            \
   ['prom-env-test', 'boot-serial-test']
 
+qtests_npcm7xx = ['npcm7xx_timer-test']
 qtests_arm = \
   (config_all_devices.has_key('CONFIG_PFLASH_CFI02') ? ['pflash-cfi02-test'] : []) +         \
+  (config_all_devices.has_key('CONFIG_NPCM7XX') ? qtests_npcm7xx : []) + \
   ['arm-cpu-features',
    'microbit-test',
    'm25p80-test',
-   'npcm7xx_timer-test',
    'test-arm-mptimer',
    'boot-serial-test',
    'hexloader-test']
diff --git a/tests/qtest/migration-helpers.c b/tests/qtest/migration-helpers.c
index b799dba..4ee2601 100644
--- a/tests/qtest/migration-helpers.c
+++ b/tests/qtest/migration-helpers.c
@@ -32,7 +32,7 @@ static void check_stop_event(QTestState *who)
 QDict *wait_command_fd(QTestState *who, int fd, const char *command, ...)
 {
     va_list ap;
-    QDict *resp;
+    QDict *resp, *ret;
 
     va_start(ap, command);
     qtest_qmp_vsend_fds(who, &fd, 1, command, ap);
@@ -44,7 +44,11 @@ QDict *wait_command_fd(QTestState *who, int fd, const char *command, ...)
     g_assert(!qdict_haskey(resp, "error"));
     g_assert(qdict_haskey(resp, "return"));
 
-    return qdict_get_qdict(resp, "return");
+    ret = qdict_get_qdict(resp, "return");
+    qobject_ref(ret);
+    qobject_unref(resp);
+
+    return ret;
 }
 
 /*
@@ -53,7 +57,7 @@ QDict *wait_command_fd(QTestState *who, int fd, const char *command, ...)
 QDict *wait_command(QTestState *who, const char *command, ...)
 {
     va_list ap;
-    QDict *resp;
+    QDict *resp, *ret;
 
     va_start(ap, command);
     resp = qtest_vqmp(who, command, ap);
@@ -64,7 +68,11 @@ QDict *wait_command(QTestState *who, const char *command, ...)
     g_assert(!qdict_haskey(resp, "error"));
     g_assert(qdict_haskey(resp, "return"));
 
-    return qdict_get_qdict(resp, "return");
+    ret = qdict_get_qdict(resp, "return");
+    qobject_ref(ret);
+    qobject_unref(resp);
+
+    return ret;
 }
 
 /*