Merge tag 'mem-2022-10-28' of https://github.com/davidhildenbrand/qemu into staging

Hi,

"Host Memory Backends" and "Memory devices" queue ("mem"):
- Fix NVDIMM error message
- Add ThreadContext user-creatable object and wire it up for NUMA-aware
  hostmem preallocation

# -----BEGIN PGP SIGNATURE-----
#
# iQJFBAABCAAvFiEEG9nKrXNcTDpGDfzKTd4Q9wD/g1oFAmNbpHARHGRhdmlkQHJl
# ZGhhdC5jb20ACgkQTd4Q9wD/g1pDpw//bG9cyIlzTzDnU5pbQiXyLm0nF9tW/tli
# npGPSbFFYz/72XD9VJSVLhbNHoQSmFcMK5m/DA4WAMdOc5zF7lP3XdZcj72pDyxu
# 31hJRvuRhxNb09jhEdWRfX5+Jg9UyYXuIvtKXHSWgrtaYDtHBdTXq/ojZlvlo/rr
# 36v0jaVaTNRs7dKQL2oaN+DSMiPXHxBzA6FABqYmJNNwuMJT0kkX8pfz0OFwkRn+
# iqf9uRhM6b/fNNB0+ReA7FfGL+hzU6Uv8AvAL3orXUqjwPMRe9Fz2gE7HpFnE6DD
# dOP4Xk2iSSJ5XQA8HwtvrQfrGPh4gPYE80ziK/+8boy3alVeGYbYbvWVtdsNju41
# Cq9kM1wDyjZf6SSUIAbjOrNPdbhwyK4GviVBR1zh+/gA3uF5MhrDtZh4h3mWX2if
# ijmT9mfte4NwF3K1MvckAl7IHRb8nxmr7wjjhJ26JwpD+76lfAcmXC2YOlFGHCMi
# 028mjvThf3HW7BD2LjlQSX4UkHmM2vUBrgMGQKyeMham1VmMfSK32wzvUNfF7xSz
# o9k0loBh7unGcUsv3EbqUGswV5F6AgjK3vWRkDql8dNrdIoapDfaejPCd58kVM98
# 5N/aEoha4bAeJ6NGIKzD+4saiMxUqJ0y2NjSrE8iO4HszXgZW5e1Gbkn4Ae6d37D
# QSSqyfasVHY=
# =bLuc
# -----END PGP SIGNATURE-----
# gpg: Signature made Fri 28 Oct 2022 05:44:16 EDT
# gpg:                using RSA key 1BD9CAAD735C4C3A460DFCCA4DDE10F700FF835A
# gpg:                issuer "david@redhat.com"
# gpg: Good signature from "David Hildenbrand <david@redhat.com>" [unknown]
# gpg:                 aka "David Hildenbrand <davidhildenbrand@gmail.com>" [full]
# gpg:                 aka "David Hildenbrand <hildenbr@in.tum.de>" [unknown]
# gpg: WARNING: The key's User ID is not certified with a trusted signature!
# gpg:          There is no indication that the signature belongs to the owner.
# Primary key fingerprint: 1BD9 CAAD 735C 4C3A 460D  FCCA 4DDE 10F7 00FF 835A

* tag 'mem-2022-10-28' of https://github.com/davidhildenbrand/qemu:
  vl: Allow ThreadContext objects to be created before the sandbox option
  hostmem: Allow for specifying a ThreadContext for preallocation
  util: Make qemu_prealloc_mem() optionally consume a ThreadContext
  util: Add write-only "node-affinity" property for ThreadContext
  util: Introduce ThreadContext user-creatable object
  util: Introduce qemu_thread_set_affinity() and qemu_thread_get_affinity()
  util: Cleanup and rename os_mem_prealloc()
  hw/mem/nvdimm: fix error message for 'unarmed' flag

Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>

17 files changed, 642 insertions, 31 deletions

diff --git a/backends/hostmem.c b/backends/hostmem.c
index 4428e06..8640294 100644
--- a/backends/hostmem.c
+++ b/backends/hostmem.c
@@ -232,7 +232,8 @@ static void host_memory_backend_set_prealloc(Object *obj, bool value,
         void *ptr = memory_region_get_ram_ptr(&backend->mr);
         uint64_t sz = memory_region_size(&backend->mr);
 
-        os_mem_prealloc(fd, ptr, sz, backend->prealloc_threads, &local_err);
+        qemu_prealloc_mem(fd, ptr, sz, backend->prealloc_threads,
+                          backend->prealloc_context, &local_err);
         if (local_err) {
             error_propagate(errp, local_err);
             return;
@@ -383,8 +384,9 @@ host_memory_backend_memory_complete(UserCreatable *uc, Error **errp)
          * specified NUMA policy in place.
          */
         if (backend->prealloc) {
-            os_mem_prealloc(memory_region_get_fd(&backend->mr), ptr, sz,
-                            backend->prealloc_threads, &local_err);
+            qemu_prealloc_mem(memory_region_get_fd(&backend->mr), ptr, sz,
+                              backend->prealloc_threads,
+                              backend->prealloc_context, &local_err);
             if (local_err) {
                 goto out;
             }
@@ -492,6 +494,11 @@ host_memory_backend_class_init(ObjectClass *oc, void *data)
         NULL, NULL);
     object_class_property_set_description(oc, "prealloc-threads",
         "Number of CPU threads to use for prealloc");
+    object_class_property_add_link(oc, "prealloc-context",
+        TYPE_THREAD_CONTEXT, offsetof(HostMemoryBackend, prealloc_context),
+        object_property_allow_set_link, OBJ_PROP_LINK_STRONG);
+    object_class_property_set_description(oc, "prealloc-context",
+        "Context to use for creating CPU threads for preallocation");
     object_class_property_add(oc, "size", "int",
         host_memory_backend_get_size,
         host_memory_backend_set_size,
diff --git a/hw/mem/nvdimm.c b/hw/mem/nvdimm.c
index 7c7d777..31080c2 100644
--- a/hw/mem/nvdimm.c
+++ b/hw/mem/nvdimm.c
@@ -149,7 +149,7 @@ static void nvdimm_prepare_memory_region(NVDIMMDevice *nvdimm, Error **errp)
     if (!nvdimm->unarmed && memory_region_is_rom(mr)) {
         HostMemoryBackend *hostmem = dimm->hostmem;
 
-        error_setg(errp, "'unarmed' property must be off since memdev %s "
+        error_setg(errp, "'unarmed' property must be 'on' since memdev %s "
                    "is read-only",
                    object_get_canonical_path_component(OBJECT(hostmem)));
         return;
diff --git a/hw/virtio/virtio-mem.c b/hw/virtio/virtio-mem.c
index 30d03e9..ed170de 100644
--- a/hw/virtio/virtio-mem.c
+++ b/hw/virtio/virtio-mem.c
@@ -467,7 +467,7 @@ static int virtio_mem_set_block_state(VirtIOMEM *vmem, uint64_t start_gpa,
             int fd = memory_region_get_fd(&vmem->memdev->mr);
             Error *local_err = NULL;
 
-            os_mem_prealloc(fd, area, size, 1, &local_err);
+            qemu_prealloc_mem(fd, area, size, 1, NULL, &local_err);
             if (local_err) {
                 static bool warned;
 
diff --git a/include/qemu/osdep.h b/include/qemu/osdep.h
index 2276094..b9c4307 100644
--- a/include/qemu/osdep.h
+++ b/include/qemu/osdep.h
@@ -576,8 +576,23 @@ unsigned long qemu_getauxval(unsigned long type);
 
 void qemu_set_tty_echo(int fd, bool echo);
 
-void os_mem_prealloc(int fd, char *area, size_t sz, int smp_cpus,
-                     Error **errp);
+typedef struct ThreadContext ThreadContext;
+
+/**
+ * qemu_prealloc_mem:
+ * @fd: the fd mapped into the area, -1 for anonymous memory
+ * @area: start address of the are to preallocate
+ * @sz: the size of the area to preallocate
+ * @max_threads: maximum number of threads to use
+ * @errp: returns an error if this function fails
+ *
+ * Preallocate memory (populate/prefault page tables writable) for the virtual
+ * memory area starting at @area with the size of @sz. After a successful call,
+ * each page in the area was faulted in writable at least once, for example,
+ * after allocating file blocks for mapped files.
+ */
+void qemu_prealloc_mem(int fd, char *area, size_t sz, int max_threads,
+                       ThreadContext *tc, Error **errp);
 
 /**
  * qemu_get_pid_name:
diff --git a/include/qemu/thread-context.h b/include/qemu/thread-context.h
new file mode 100644
index 0000000..2ebd6b7
--- /dev/null
+++ b/include/qemu/thread-context.h
@@ -0,0 +1,57 @@
+/*
+ * QEMU Thread Context
+ *
+ * Copyright Red Hat Inc., 2022
+ *
+ * Authors:
+ *  David Hildenbrand <david@redhat.com>
+ *
+ * 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 SYSEMU_THREAD_CONTEXT_H
+#define SYSEMU_THREAD_CONTEXT_H
+
+#include "qapi/qapi-types-machine.h"
+#include "qemu/thread.h"
+#include "qom/object.h"
+
+#define TYPE_THREAD_CONTEXT "thread-context"
+OBJECT_DECLARE_TYPE(ThreadContext, ThreadContextClass,
+                    THREAD_CONTEXT)
+
+struct ThreadContextClass {
+    ObjectClass parent_class;
+};
+
+struct ThreadContext {
+    /* private */
+    Object parent;
+
+    /* private */
+    unsigned int thread_id;
+    QemuThread thread;
+
+    /* Semaphore to wait for context thread action. */
+    QemuSemaphore sem;
+    /* Semaphore to wait for action in context thread. */
+    QemuSemaphore sem_thread;
+    /* Mutex to synchronize requests. */
+    QemuMutex mutex;
+
+    /* Commands for the thread to execute. */
+    int thread_cmd;
+    void *thread_cmd_data;
+
+    /* CPU affinity bitmap used for initialization. */
+    unsigned long *init_cpu_bitmap;
+    int init_cpu_nbits;
+};
+
+void thread_context_create_thread(ThreadContext *tc, QemuThread *thread,
+                                  const char *name,
+                                  void *(*start_routine)(void *), void *arg,
+                                  int mode);
+
+#endif /* SYSEMU_THREAD_CONTEXT_H */
diff --git a/include/qemu/thread.h b/include/qemu/thread.h
index 20641e5..7c6703b 100644
--- a/include/qemu/thread.h
+++ b/include/qemu/thread.h
@@ -185,6 +185,10 @@ void qemu_event_destroy(QemuEvent *ev);
 void qemu_thread_create(QemuThread *thread, const char *name,
                         void *(*start_routine)(void *),
                         void *arg, int mode);
+int qemu_thread_set_affinity(QemuThread *thread, unsigned long *host_cpus,
+                             unsigned long nbits);
+int qemu_thread_get_affinity(QemuThread *thread, unsigned long **host_cpus,
+                             unsigned long *nbits);
 void *qemu_thread_join(QemuThread *thread);
 void qemu_thread_get_self(QemuThread *thread);
 bool qemu_thread_is_self(QemuThread *thread);
diff --git a/include/sysemu/hostmem.h b/include/sysemu/hostmem.h
index 9ff5c16..39326f1 100644
--- a/include/sysemu/hostmem.h
+++ b/include/sysemu/hostmem.h
@@ -18,6 +18,7 @@
 #include "qom/object.h"
 #include "exec/memory.h"
 #include "qemu/bitmap.h"
+#include "qemu/thread-context.h"
 
 #define TYPE_MEMORY_BACKEND "memory-backend"
 OBJECT_DECLARE_TYPE(HostMemoryBackend, HostMemoryBackendClass,
@@ -66,6 +67,7 @@ struct HostMemoryBackend {
     bool merge, dump, use_canonical_path;
     bool prealloc, is_mapped, share, reserve;
     uint32_t prealloc_threads;
+    ThreadContext *prealloc_context;
     DECLARE_BITMAP(host_nodes, MAX_NODES + 1);
     HostMemPolicy policy;
 
diff --git a/meson.build b/meson.build
index 7d39756..15dff0a 100644
--- a/meson.build
+++ b/meson.build
@@ -2130,7 +2130,23 @@ config_host_data.set('CONFIG_PTHREAD_CONDATTR_SETCLOCK', cc.links(gnu_source_pre
     pthread_condattr_setclock(&attr, CLOCK_MONOTONIC);
     return 0;
   }''', dependencies: threads))
+config_host_data.set('CONFIG_PTHREAD_AFFINITY_NP', cc.links(gnu_source_prefix + '''
+  #include <pthread.h>
 
+  static void *f(void *p) { return NULL; }
+  int main(void)
+  {
+    int setsize = CPU_ALLOC_SIZE(64);
+    pthread_t thread;
+    cpu_set_t *cpuset;
+    pthread_create(&thread, 0, f, 0);
+    cpuset = CPU_ALLOC(64);
+    CPU_ZERO_S(setsize, cpuset);
+    pthread_setaffinity_np(thread, setsize, cpuset);
+    pthread_getaffinity_np(thread, setsize, cpuset);
+    CPU_FREE(cpuset);
+    return 0;
+  }''', dependencies: threads))
 config_host_data.set('CONFIG_SIGNALFD', cc.links(gnu_source_prefix + '''
   #include <sys/signalfd.h>
   #include <stddef.h>
diff --git a/qapi/qom.json b/qapi/qom.json
index 80dd419..87fcad2 100644
--- a/qapi/qom.json
+++ b/qapi/qom.json
@@ -578,6 +578,9 @@
 #
 # @prealloc-threads: number of CPU threads to use for prealloc (default: 1)
 #
+# @prealloc-context: thread context to use for creation of preallocation threads
+#                    (default: none) (since 7.2)
+#
 # @share: if false, the memory is private to QEMU; if true, it is shared
 #         (default: false)
 #
@@ -608,6 +611,7 @@
             '*policy': 'HostMemPolicy',
             '*prealloc': 'bool',
             '*prealloc-threads': 'uint32',
+            '*prealloc-context': 'str',
             '*share': 'bool',
             '*reserve': 'bool',
             'size': 'size',
@@ -831,6 +835,28 @@
             '*kernel-hashes': 'bool' } }
 
 ##
+# @ThreadContextProperties:
+#
+# Properties for thread context objects.
+#
+# @cpu-affinity: the list of host CPU numbers used as CPU affinity for all
+#                threads created in the thread context (default: QEMU main
+#                thread CPU affinity)
+#
+# @node-affinity: the list of host node numbers that will be resolved to a
+#                 list of host CPU numbers used as CPU affinity. This is a
+#                 shortcut for specifying the list of host CPU numbers
+#                 belonging to the host nodes manually by setting
+#                 @cpu-affinity. (default: QEMU main thread affinity)
+#
+# Since: 7.2
+##
+{ 'struct': 'ThreadContextProperties',
+  'data': { '*cpu-affinity': ['uint16'],
+            '*node-affinity': ['uint16'] } }
+
+
+##
 # @ObjectType:
 #
 # Features:
@@ -882,6 +908,7 @@
     { 'name': 'secret_keyring',
       'if': 'CONFIG_SECRET_KEYRING' },
     'sev-guest',
+    'thread-context',
     's390-pv-guest',
     'throttle-group',
     'tls-creds-anon',
@@ -948,6 +975,7 @@
       'secret_keyring':             { 'type': 'SecretKeyringProperties',
                                       'if': 'CONFIG_SECRET_KEYRING' },
       'sev-guest':                  'SevGuestProperties',
+      'thread-context':             'ThreadContextProperties',
       'throttle-group':             'ThrottleGroupProperties',
       'tls-creds-anon':             'TlsCredsAnonProperties',
       'tls-creds-psk':              'TlsCredsPskProperties',
diff --git a/softmmu/cpus.c b/softmmu/cpus.c
index 61b27ff..01c94fd 100644
--- a/softmmu/cpus.c
+++ b/softmmu/cpus.c
@@ -354,7 +354,7 @@ static void qemu_init_sigbus(void)
 
     /*
      * ALERT: when modifying this, take care that SIGBUS forwarding in
-     * os_mem_prealloc() will continue working as expected.
+     * qemu_prealloc_mem() will continue working as expected.
      */
     memset(&action, 0, sizeof(action));
     action.sa_flags = SA_SIGINFO;
diff --git a/softmmu/vl.c b/softmmu/vl.c
index 99fb49c..5115221 100644
--- a/softmmu/vl.c
+++ b/softmmu/vl.c
@@ -1760,6 +1760,27 @@ static void object_option_parse(const char *optarg)
 }
 
 /*
+ * Very early object creation, before the sandbox options have been activated.
+ */
+static bool object_create_pre_sandbox(const char *type)
+{
+    /*
+     * Objects should in general not get initialized "too early" without
+     * a reason. If you add one, state the reason in a comment!
+     */
+
+    /*
+     * Reason: -sandbox on,resourcecontrol=deny disallows setting CPU
+     * affinity of threads.
+     */
+    if (g_str_equal(type, "thread-context")) {
+        return true;
+    }
+
+    return false;
+}
+
+/*
  * Initial object creation happens before all other
  * QEMU data types are created. The majority of objects
  * can be created at this point. The rng-egd object
@@ -1773,6 +1794,11 @@ static bool object_create_early(const char *type)
      * add one, state the reason in a comment!
      */
 
+    /* Reason: already created. */
+    if (object_create_pre_sandbox(type)) {
+        return false;
+    }
+
     /* Reason: property "chardev" */
     if (g_str_equal(type, "rng-egd") ||
         g_str_equal(type, "qtest")) {
@@ -1895,7 +1921,7 @@ static void qemu_create_early_backends(void)
  */
 static bool object_create_late(const char *type)
 {
-    return !object_create_early(type);
+    return !object_create_early(type) && !object_create_pre_sandbox(type);
 }
 
 static void qemu_create_late_backends(void)
@@ -2351,6 +2377,11 @@ static int process_runstate_actions(void *opaque, QemuOpts *opts, Error **errp)
 
 static void qemu_process_early_options(void)
 {
+    qemu_opts_foreach(qemu_find_opts("name"),
+                      parse_name, NULL, &error_fatal);
+
+    object_option_foreach_add(object_create_pre_sandbox);
+
 #ifdef CONFIG_SECCOMP
     QemuOptsList *olist = qemu_find_opts_err("sandbox", NULL);
     if (olist) {
@@ -2358,9 +2389,6 @@ static void qemu_process_early_options(void)
     }
 #endif
 
-    qemu_opts_foreach(qemu_find_opts("name"),
-                      parse_name, NULL, &error_fatal);
-
     if (qemu_opts_foreach(qemu_find_opts("action"),
                           process_runstate_actions, NULL, &error_fatal)) {
         exit(1);
diff --git a/util/meson.build b/util/meson.build
index 5e28213..c0a7bc5 100644
--- a/util/meson.build
+++ b/util/meson.build
@@ -1,4 +1,5 @@
 util_ss.add(files('osdep.c', 'cutils.c', 'unicode.c', 'qemu-timer-common.c'))
+util_ss.add(files('thread-context.c'), numa)
 if not config_host_data.get('CONFIG_ATOMIC64')
   util_ss.add(files('atomic64.c'))
 endif
diff --git a/util/oslib-posix.c b/util/oslib-posix.c
index 827a7aa..59a891b 100644
--- a/util/oslib-posix.c
+++ b/util/oslib-posix.c
@@ -42,6 +42,7 @@
 #include "qemu/cutils.h"
 #include "qemu/compiler.h"
 #include "qemu/units.h"
+#include "qemu/thread-context.h"
 
 #ifdef CONFIG_LINUX
 #include <sys/syscall.h>
@@ -329,7 +330,7 @@ static void sigbus_handler(int signal)
         return;
     }
 #endif /* CONFIG_LINUX */
-    warn_report("os_mem_prealloc: unrelated SIGBUS detected and ignored");
+    warn_report("qemu_prealloc_mem: unrelated SIGBUS detected and ignored");
 }
 
 static void *do_touch_pages(void *arg)
@@ -399,13 +400,13 @@ static void *do_madv_populate_write_pages(void *arg)
 }
 
 static inline int get_memset_num_threads(size_t hpagesize, size_t numpages,
-                                         int smp_cpus)
+                                         int max_threads)
 {
     long host_procs = sysconf(_SC_NPROCESSORS_ONLN);
     int ret = 1;
 
     if (host_procs > 0) {
-        ret = MIN(MIN(host_procs, MAX_MEM_PREALLOC_THREAD_COUNT), smp_cpus);
+        ret = MIN(MIN(host_procs, MAX_MEM_PREALLOC_THREAD_COUNT), max_threads);
     }
 
     /* Especially with gigantic pages, don't create more threads than pages. */
@@ -418,11 +419,12 @@ static inline int get_memset_num_threads(size_t hpagesize, size_t numpages,
 }
 
 static int touch_all_pages(char *area, size_t hpagesize, size_t numpages,
-                           int smp_cpus, bool use_madv_populate_write)
+                           int max_threads, ThreadContext *tc,
+                           bool use_madv_populate_write)
 {
     static gsize initialized = 0;
     MemsetContext context = {
-        .num_threads = get_memset_num_threads(hpagesize, numpages, smp_cpus),
+        .num_threads = get_memset_num_threads(hpagesize, numpages, max_threads),
     };
     size_t numpages_per_thread, leftover;
     void *(*touch_fn)(void *);
@@ -457,9 +459,16 @@ static int touch_all_pages(char *area, size_t hpagesize, size_t numpages,
         context.threads[i].numpages = numpages_per_thread + (i < leftover);
         context.threads[i].hpagesize = hpagesize;
         context.threads[i].context = &context;
-        qemu_thread_create(&context.threads[i].pgthread, "touch_pages",
-                           touch_fn, &context.threads[i],
-                           QEMU_THREAD_JOINABLE);
+        if (tc) {
+            thread_context_create_thread(tc, &context.threads[i].pgthread,
+                                         "touch_pages",
+                                         touch_fn, &context.threads[i],
+                                         QEMU_THREAD_JOINABLE);
+        } else {
+            qemu_thread_create(&context.threads[i].pgthread, "touch_pages",
+                               touch_fn, &context.threads[i],
+                               QEMU_THREAD_JOINABLE);
+        }
         addr += context.threads[i].numpages * hpagesize;
     }
 
@@ -494,13 +503,13 @@ static bool madv_populate_write_possible(char *area, size_t pagesize)
            errno != EINVAL;
 }
 
-void os_mem_prealloc(int fd, char *area, size_t memory, int smp_cpus,
-                     Error **errp)
+void qemu_prealloc_mem(int fd, char *area, size_t sz, int max_threads,
+                       ThreadContext *tc, Error **errp)
 {
     static gsize initialized;
     int ret;
     size_t hpagesize = qemu_fd_getpagesize(fd);
-    size_t numpages = DIV_ROUND_UP(memory, hpagesize);
+    size_t numpages = DIV_ROUND_UP(sz, hpagesize);
     bool use_madv_populate_write;
     struct sigaction act;
 
@@ -530,24 +539,24 @@ void os_mem_prealloc(int fd, char *area, size_t memory, int smp_cpus,
         if (ret) {
             qemu_mutex_unlock(&sigbus_mutex);
             error_setg_errno(errp, errno,
-                "os_mem_prealloc: failed to install signal handler");
+                "qemu_prealloc_mem: failed to install signal handler");
             return;
         }
     }
 
     /* touch pages simultaneously */
-    ret = touch_all_pages(area, hpagesize, numpages, smp_cpus,
+    ret = touch_all_pages(area, hpagesize, numpages, max_threads, tc,
                           use_madv_populate_write);
     if (ret) {
         error_setg_errno(errp, -ret,
-                         "os_mem_prealloc: preallocating memory failed");
+                         "qemu_prealloc_mem: preallocating memory failed");
     }
 
     if (!use_madv_populate_write) {
         ret = sigaction(SIGBUS, &sigbus_oldact, NULL);
         if (ret) {
             /* Terminate QEMU since it can't recover from error */
-            perror("os_mem_prealloc: failed to reinstall signal handler");
+            perror("qemu_prealloc_mem: failed to reinstall signal handler");
             exit(1);
         }
         qemu_mutex_unlock(&sigbus_mutex);
diff --git a/util/oslib-win32.c b/util/oslib-win32.c
index 5723d3e..a67cb38 100644
--- a/util/oslib-win32.c
+++ b/util/oslib-win32.c
@@ -268,14 +268,14 @@ int getpagesize(void)
     return system_info.dwPageSize;
 }
 
-void os_mem_prealloc(int fd, char *area, size_t memory, int smp_cpus,
-                     Error **errp)
+void qemu_prealloc_mem(int fd, char *area, size_t sz, int max_threads,
+                       ThreadContext *tc, Error **errp)
 {
     int i;
     size_t pagesize = qemu_real_host_page_size();
 
-    memory = (memory + pagesize - 1) & -pagesize;
-    for (i = 0; i < memory / pagesize; i++) {
+    sz = (sz + pagesize - 1) & -pagesize;
+    for (i = 0; i < sz / pagesize; i++) {
         memset(area + pagesize * i, 0, 1);
     }
 }
diff --git a/util/qemu-thread-posix.c b/util/qemu-thread-posix.c
index ac1d56e..bae938c 100644
--- a/util/qemu-thread-posix.c
+++ b/util/qemu-thread-posix.c
@@ -16,6 +16,7 @@
 #include "qemu/notify.h"
 #include "qemu-thread-common.h"
 #include "qemu/tsan.h"
+#include "qemu/bitmap.h"
 
 static bool name_threads;
 
@@ -552,6 +553,75 @@ void qemu_thread_create(QemuThread *thread, const char *name,
     pthread_attr_destroy(&attr);
 }
 
+int qemu_thread_set_affinity(QemuThread *thread, unsigned long *host_cpus,
+                             unsigned long nbits)
+{
+#if defined(CONFIG_PTHREAD_AFFINITY_NP)
+    const size_t setsize = CPU_ALLOC_SIZE(nbits);
+    unsigned long value;
+    cpu_set_t *cpuset;
+    int err;
+
+    cpuset = CPU_ALLOC(nbits);
+    g_assert(cpuset);
+
+    CPU_ZERO_S(setsize, cpuset);
+    value = find_first_bit(host_cpus, nbits);
+    while (value < nbits) {
+        CPU_SET_S(value, setsize, cpuset);
+        value = find_next_bit(host_cpus, nbits, value + 1);
+    }
+
+    err = pthread_setaffinity_np(thread->thread, setsize, cpuset);
+    CPU_FREE(cpuset);
+    return err;
+#else
+    return -ENOSYS;
+#endif
+}
+
+int qemu_thread_get_affinity(QemuThread *thread, unsigned long **host_cpus,
+                             unsigned long *nbits)
+{
+#if defined(CONFIG_PTHREAD_AFFINITY_NP)
+    unsigned long tmpbits;
+    cpu_set_t *cpuset;
+    size_t setsize;
+    int i, err;
+
+    tmpbits = CPU_SETSIZE;
+    while (true) {
+        setsize = CPU_ALLOC_SIZE(tmpbits);
+        cpuset = CPU_ALLOC(tmpbits);
+        g_assert(cpuset);
+
+        err = pthread_getaffinity_np(thread->thread, setsize, cpuset);
+        if (err) {
+            CPU_FREE(cpuset);
+            if (err != -EINVAL) {
+                return err;
+            }
+            tmpbits *= 2;
+        } else {
+            break;
+        }
+    }
+
+    /* Convert the result into a proper bitmap. */
+    *nbits = tmpbits;
+    *host_cpus = bitmap_new(tmpbits);
+    for (i = 0; i < tmpbits; i++) {
+        if (CPU_ISSET(i, cpuset)) {
+            set_bit(i, *host_cpus);
+        }
+    }
+    CPU_FREE(cpuset);
+    return 0;
+#else
+    return -ENOSYS;
+#endif
+}
+
 void qemu_thread_get_self(QemuThread *thread)
 {
     thread->thread = pthread_self();
diff --git a/util/qemu-thread-win32.c b/util/qemu-thread-win32.c
index b9a467d..69db254 100644
--- a/util/qemu-thread-win32.c
+++ b/util/qemu-thread-win32.c
@@ -477,6 +477,18 @@ void qemu_thread_create(QemuThread *thread, const char *name,
     thread->data = data;
 }
 
+int qemu_thread_set_affinity(QemuThread *thread, unsigned long *host_cpus,
+                             unsigned long nbits)
+{
+    return -ENOSYS;
+}
+
+int qemu_thread_get_affinity(QemuThread *thread, unsigned long **host_cpus,
+                             unsigned long *nbits)
+{
+    return -ENOSYS;
+}
+
 void qemu_thread_get_self(QemuThread *thread)
 {
     thread->data = qemu_thread_data;
diff --git a/util/thread-context.c b/util/thread-context.c
new file mode 100644
index 0000000..4138245
--- /dev/null
+++ b/util/thread-context.c
@@ -0,0 +1,362 @@
+/*
+ * QEMU Thread Context
+ *
+ * Copyright Red Hat Inc., 2022
+ *
+ * Authors:
+ *  David Hildenbrand <david@redhat.com>
+ *
+ * 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 "qemu/thread-context.h"
+#include "qapi/error.h"
+#include "qapi/qapi-builtin-visit.h"
+#include "qapi/visitor.h"
+#include "qemu/config-file.h"
+#include "qapi/qapi-builtin-visit.h"
+#include "qom/object_interfaces.h"
+#include "qemu/module.h"
+#include "qemu/bitmap.h"
+
+#ifdef CONFIG_NUMA
+#include <numa.h>
+#endif
+
+enum {
+    TC_CMD_NONE = 0,
+    TC_CMD_STOP,
+    TC_CMD_NEW,
+};
+
+typedef struct ThreadContextCmdNew {
+    QemuThread *thread;
+    const char *name;
+    void *(*start_routine)(void *);
+    void *arg;
+    int mode;
+} ThreadContextCmdNew;
+
+static void *thread_context_run(void *opaque)
+{
+    ThreadContext *tc = opaque;
+
+    tc->thread_id = qemu_get_thread_id();
+    qemu_sem_post(&tc->sem);
+
+    while (true) {
+        /*
+         * Threads inherit the CPU affinity of the creating thread. For this
+         * reason, we create new (especially short-lived) threads from our
+         * persistent context thread.
+         *
+         * Especially when QEMU is not allowed to set the affinity itself,
+         * management tools can simply set the affinity of the context thread
+         * after creating the context, to have new threads created via
+         * the context inherit the CPU affinity automatically.
+         */
+        switch (tc->thread_cmd) {
+        case TC_CMD_NONE:
+            break;
+        case TC_CMD_STOP:
+            tc->thread_cmd = TC_CMD_NONE;
+            qemu_sem_post(&tc->sem);
+            return NULL;
+        case TC_CMD_NEW: {
+            ThreadContextCmdNew *cmd_new = tc->thread_cmd_data;
+
+            qemu_thread_create(cmd_new->thread, cmd_new->name,
+                               cmd_new->start_routine, cmd_new->arg,
+                               cmd_new->mode);
+            tc->thread_cmd = TC_CMD_NONE;
+            tc->thread_cmd_data = NULL;
+            qemu_sem_post(&tc->sem);
+            break;
+        }
+        default:
+            g_assert_not_reached();
+        }
+        qemu_sem_wait(&tc->sem_thread);
+    }
+}
+
+static void thread_context_set_cpu_affinity(Object *obj, Visitor *v,
+                                            const char *name, void *opaque,
+                                            Error **errp)
+{
+    ThreadContext *tc = THREAD_CONTEXT(obj);
+    uint16List *l, *host_cpus = NULL;
+    unsigned long *bitmap = NULL;
+    int nbits = 0, ret;
+    Error *err = NULL;
+
+    if (tc->init_cpu_bitmap) {
+        error_setg(errp, "Mixing CPU and node affinity not supported");
+        return;
+    }
+
+    visit_type_uint16List(v, name, &host_cpus, &err);
+    if (err) {
+        error_propagate(errp, err);
+        return;
+    }
+
+    if (!host_cpus) {
+        error_setg(errp, "CPU list is empty");
+        goto out;
+    }
+
+    for (l = host_cpus; l; l = l->next) {
+        nbits = MAX(nbits, l->value + 1);
+    }
+    bitmap = bitmap_new(nbits);
+    for (l = host_cpus; l; l = l->next) {
+        set_bit(l->value, bitmap);
+    }
+
+    if (tc->thread_id != -1) {
+        /*
+         * Note: we won't be adjusting the affinity of any thread that is still
+         * around, but only the affinity of the context thread.
+         */
+        ret = qemu_thread_set_affinity(&tc->thread, bitmap, nbits);
+        if (ret) {
+            error_setg(errp, "Setting CPU affinity failed: %s", strerror(ret));
+        }
+    } else {
+        tc->init_cpu_bitmap = bitmap;
+        bitmap = NULL;
+        tc->init_cpu_nbits = nbits;
+    }
+out:
+    g_free(bitmap);
+    qapi_free_uint16List(host_cpus);
+}
+
+static void thread_context_get_cpu_affinity(Object *obj, Visitor *v,
+                                            const char *name, void *opaque,
+                                            Error **errp)
+{
+    unsigned long *bitmap, nbits, value;
+    ThreadContext *tc = THREAD_CONTEXT(obj);
+    uint16List *host_cpus = NULL;
+    uint16List **tail = &host_cpus;
+    int ret;
+
+    if (tc->thread_id == -1) {
+        error_setg(errp, "Object not initialized yet");
+        return;
+    }
+
+    ret = qemu_thread_get_affinity(&tc->thread, &bitmap, &nbits);
+    if (ret) {
+        error_setg(errp, "Getting CPU affinity failed: %s", strerror(ret));
+        return;
+    }
+
+    value = find_first_bit(bitmap, nbits);
+    while (value < nbits) {
+        QAPI_LIST_APPEND(tail, value);
+
+        value = find_next_bit(bitmap, nbits, value + 1);
+    }
+    g_free(bitmap);
+
+    visit_type_uint16List(v, name, &host_cpus, errp);
+    qapi_free_uint16List(host_cpus);
+}
+
+static void thread_context_set_node_affinity(Object *obj, Visitor *v,
+                                             const char *name, void *opaque,
+                                             Error **errp)
+{
+#ifdef CONFIG_NUMA
+    const int nbits = numa_num_possible_cpus();
+    ThreadContext *tc = THREAD_CONTEXT(obj);
+    uint16List *l, *host_nodes = NULL;
+    unsigned long *bitmap = NULL;
+    struct bitmask *tmp_cpus;
+    Error *err = NULL;
+    int ret, i;
+
+    if (tc->init_cpu_bitmap) {
+        error_setg(errp, "Mixing CPU and node affinity not supported");
+        return;
+    }
+
+    visit_type_uint16List(v, name, &host_nodes, &err);
+    if (err) {
+        error_propagate(errp, err);
+        return;
+    }
+
+    if (!host_nodes) {
+        error_setg(errp, "Node list is empty");
+        goto out;
+    }
+
+    bitmap = bitmap_new(nbits);
+    tmp_cpus = numa_allocate_cpumask();
+    for (l = host_nodes; l; l = l->next) {
+        numa_bitmask_clearall(tmp_cpus);
+        ret = numa_node_to_cpus(l->value, tmp_cpus);
+        if (ret) {
+            /* We ignore any errors, such as impossible nodes. */
+            continue;
+        }
+        for (i = 0; i < nbits; i++) {
+            if (numa_bitmask_isbitset(tmp_cpus, i)) {
+                set_bit(i, bitmap);
+            }
+        }
+    }
+    numa_free_cpumask(tmp_cpus);
+
+    if (bitmap_empty(bitmap, nbits)) {
+        error_setg(errp, "The nodes select no CPUs");
+        goto out;
+    }
+
+    if (tc->thread_id != -1) {
+        /*
+         * Note: we won't be adjusting the affinity of any thread that is still
+         * around for now, but only the affinity of the context thread.
+         */
+        ret = qemu_thread_set_affinity(&tc->thread, bitmap, nbits);
+        if (ret) {
+            error_setg(errp, "Setting CPU affinity failed: %s", strerror(ret));
+        }
+    } else {
+        tc->init_cpu_bitmap = bitmap;
+        bitmap = NULL;
+        tc->init_cpu_nbits = nbits;
+    }
+out:
+    g_free(bitmap);
+    qapi_free_uint16List(host_nodes);
+#else
+    error_setg(errp, "NUMA node affinity is not supported by this QEMU");
+#endif
+}
+
+static void thread_context_get_thread_id(Object *obj, Visitor *v,
+                                         const char *name, void *opaque,
+                                         Error **errp)
+{
+    ThreadContext *tc = THREAD_CONTEXT(obj);
+    uint64_t value = tc->thread_id;
+
+    visit_type_uint64(v, name, &value, errp);
+}
+
+static void thread_context_instance_complete(UserCreatable *uc, Error **errp)
+{
+    ThreadContext *tc = THREAD_CONTEXT(uc);
+    char *thread_name;
+    int ret;
+
+    thread_name = g_strdup_printf("TC %s",
+                               object_get_canonical_path_component(OBJECT(uc)));
+    qemu_thread_create(&tc->thread, thread_name, thread_context_run, tc,
+                       QEMU_THREAD_JOINABLE);
+    g_free(thread_name);
+
+    /* Wait until initialization of the thread is done. */
+    while (tc->thread_id == -1) {
+        qemu_sem_wait(&tc->sem);
+    }
+
+    if (tc->init_cpu_bitmap) {
+        ret = qemu_thread_set_affinity(&tc->thread, tc->init_cpu_bitmap,
+                                       tc->init_cpu_nbits);
+        if (ret) {
+            error_setg(errp, "Setting CPU affinity failed: %s", strerror(ret));
+        }
+        g_free(tc->init_cpu_bitmap);
+        tc->init_cpu_bitmap = NULL;
+    }
+}
+
+static void thread_context_class_init(ObjectClass *oc, void *data)
+{
+    UserCreatableClass *ucc = USER_CREATABLE_CLASS(oc);
+
+    ucc->complete = thread_context_instance_complete;
+    object_class_property_add(oc, "thread-id", "int",
+                              thread_context_get_thread_id, NULL, NULL,
+                              NULL);
+    object_class_property_add(oc, "cpu-affinity", "int",
+                              thread_context_get_cpu_affinity,
+                              thread_context_set_cpu_affinity, NULL, NULL);
+    object_class_property_add(oc, "node-affinity", "int", NULL,
+                              thread_context_set_node_affinity, NULL, NULL);
+}
+
+static void thread_context_instance_init(Object *obj)
+{
+    ThreadContext *tc = THREAD_CONTEXT(obj);
+
+    tc->thread_id = -1;
+    qemu_sem_init(&tc->sem, 0);
+    qemu_sem_init(&tc->sem_thread, 0);
+    qemu_mutex_init(&tc->mutex);
+}
+
+static void thread_context_instance_finalize(Object *obj)
+{
+    ThreadContext *tc = THREAD_CONTEXT(obj);
+
+    if (tc->thread_id != -1) {
+        tc->thread_cmd = TC_CMD_STOP;
+        qemu_sem_post(&tc->sem_thread);
+        qemu_thread_join(&tc->thread);
+    }
+    qemu_sem_destroy(&tc->sem);
+    qemu_sem_destroy(&tc->sem_thread);
+    qemu_mutex_destroy(&tc->mutex);
+}
+
+static const TypeInfo thread_context_info = {
+    .name = TYPE_THREAD_CONTEXT,
+    .parent = TYPE_OBJECT,
+    .class_init = thread_context_class_init,
+    .instance_size = sizeof(ThreadContext),
+    .instance_init = thread_context_instance_init,
+    .instance_finalize = thread_context_instance_finalize,
+    .interfaces = (InterfaceInfo[]) {
+        { TYPE_USER_CREATABLE },
+        { }
+    }
+};
+
+static void thread_context_register_types(void)
+{
+    type_register_static(&thread_context_info);
+}
+type_init(thread_context_register_types)
+
+void thread_context_create_thread(ThreadContext *tc, QemuThread *thread,
+                                  const char *name,
+                                  void *(*start_routine)(void *), void *arg,
+                                  int mode)
+{
+    ThreadContextCmdNew data = {
+        .thread = thread,
+        .name = name,
+        .start_routine = start_routine,
+        .arg = arg,
+        .mode = mode,
+    };
+
+    qemu_mutex_lock(&tc->mutex);
+    tc->thread_cmd = TC_CMD_NEW;
+    tc->thread_cmd_data = &data;
+    qemu_sem_post(&tc->sem_thread);
+
+    while (tc->thread_cmd != TC_CMD_NONE) {
+        qemu_sem_wait(&tc->sem);
+    }
+    qemu_mutex_unlock(&tc->mutex);
+}