Merge remote-tracking branch 'remotes/juanquintela/tags/migration/20141015' into staging

migration/next for 20141015

# gpg: Signature made Wed 15 Oct 2014 09:21:54 BST using RSA key ID 5872D723
# gpg: Can't check signature: public key not found

* remotes/juanquintela/tags/migration/20141015:
  migration: catch unknown flag combinations in ram_load
  qemu-file: Move stdio implementation to qemu-file-stdio.c
  qemu-file: Move unix and socket implementations to qemu-file-unix.c
  qemu-file: Use qemu_file_is_writable() on stdio_fclose()
  qemu-file: Make qemu_file_is_writable() non-static
  qemu-file: Add copyright header to qemu-file.c
  vmstate: Allow dynamic allocation for VBUFFER during migration
  block/migration: Disable cache invalidate for incoming migration
  Tests: QEMUSizedBuffer/QEMUBuffer
  QEMUSizedBuffer based QEMUFile

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

14 files changed, 1029 insertions, 450 deletions

diff --git a/Makefile.objs b/Makefile.objs
index add8375..18fd35c 100644
--- a/Makefile.objs
+++ b/Makefile.objs
@@ -50,7 +50,7 @@ common-obj-$(CONFIG_LINUX) += fsdev/
 
 common-obj-y += migration.o migration-tcp.o
 common-obj-y += vmstate.o
-common-obj-y += qemu-file.o
+common-obj-y += qemu-file.o qemu-file-unix.o qemu-file-stdio.o
 common-obj-$(CONFIG_RDMA) += migration-rdma.o
 common-obj-y += qemu-char.o #aio.o
 common-obj-y += block-migration.o
diff --git a/arch_init.c b/arch_init.c
index 9b3e25d..88a5ba0 100644
--- a/arch_init.c
+++ b/arch_init.c
@@ -1040,8 +1040,7 @@ void ram_handle_compressed(void *host, uint8_t ch, uint64_t size)
 
 static int ram_load(QEMUFile *f, void *opaque, int version_id)
 {
-    ram_addr_t addr;
-    int flags, ret = 0;
+    int flags = 0, ret = 0;
     static uint64_t seq_iter;
 
     seq_iter++;
@@ -1050,21 +1049,24 @@ static int ram_load(QEMUFile *f, void *opaque, int version_id)
         ret = -EINVAL;
     }
 
-    while (!ret) {
-        addr = qemu_get_be64(f);
+    while (!ret && !(flags & RAM_SAVE_FLAG_EOS)) {
+        ram_addr_t addr, total_ram_bytes;
+        void *host;
+        uint8_t ch;
 
+        addr = qemu_get_be64(f);
         flags = addr & ~TARGET_PAGE_MASK;
         addr &= TARGET_PAGE_MASK;
 
-        if (flags & RAM_SAVE_FLAG_MEM_SIZE) {
+        switch (flags & ~RAM_SAVE_FLAG_CONTINUE) {
+        case RAM_SAVE_FLAG_MEM_SIZE:
             /* Synchronize RAM block list */
-            char id[256];
-            ram_addr_t length;
-            ram_addr_t total_ram_bytes = addr;
-
-            while (total_ram_bytes) {
+            total_ram_bytes = addr;
+            while (!ret && total_ram_bytes) {
                 RAMBlock *block;
                 uint8_t len;
+                char id[256];
+                ram_addr_t length;
 
                 len = qemu_get_byte(f);
                 qemu_get_buffer(f, (uint8_t *)id, len);
@@ -1088,16 +1090,11 @@ static int ram_load(QEMUFile *f, void *opaque, int version_id)
                                  "accept migration", id);
                     ret = -EINVAL;
                 }
-                if (ret) {
-                    break;
-                }
 
                 total_ram_bytes -= length;
             }
-        } else if (flags & RAM_SAVE_FLAG_COMPRESS) {
-            void *host;
-            uint8_t ch;
-
+            break;
+        case RAM_SAVE_FLAG_COMPRESS:
             host = host_from_stream_offset(f, addr, flags);
             if (!host) {
                 error_report("Illegal RAM offset " RAM_ADDR_FMT, addr);
@@ -1107,9 +1104,8 @@ static int ram_load(QEMUFile *f, void *opaque, int version_id)
 
             ch = qemu_get_byte(f);
             ram_handle_compressed(host, ch, TARGET_PAGE_SIZE);
-        } else if (flags & RAM_SAVE_FLAG_PAGE) {
-            void *host;
-
+            break;
+        case RAM_SAVE_FLAG_PAGE:
             host = host_from_stream_offset(f, addr, flags);
             if (!host) {
                 error_report("Illegal RAM offset " RAM_ADDR_FMT, addr);
@@ -1118,8 +1114,9 @@ static int ram_load(QEMUFile *f, void *opaque, int version_id)
             }
 
             qemu_get_buffer(f, host, TARGET_PAGE_SIZE);
-        } else if (flags & RAM_SAVE_FLAG_XBZRLE) {
-            void *host = host_from_stream_offset(f, addr, flags);
+            break;
+        case RAM_SAVE_FLAG_XBZRLE:
+            host = host_from_stream_offset(f, addr, flags);
             if (!host) {
                 error_report("Illegal RAM offset " RAM_ADDR_FMT, addr);
                 ret = -EINVAL;
@@ -1132,17 +1129,22 @@ static int ram_load(QEMUFile *f, void *opaque, int version_id)
                 ret = -EINVAL;
                 break;
             }
-        } else if (flags & RAM_SAVE_FLAG_HOOK) {
-            ram_control_load_hook(f, flags);
-        } else if (flags & RAM_SAVE_FLAG_EOS) {
-            /* normal exit */
             break;
-        } else {
-            error_report("Unknown migration flags: %#x", flags);
-            ret = -EINVAL;
+        case RAM_SAVE_FLAG_EOS:
+            /* normal exit */
             break;
+        default:
+            if (flags & RAM_SAVE_FLAG_HOOK) {
+                ram_control_load_hook(f, flags);
+            } else {
+                error_report("Unknown combination of migration flags: %#x",
+                             flags);
+                ret = -EINVAL;
+            }
+        }
+        if (!ret) {
+            ret = qemu_file_get_error(f);
         }
-        ret = qemu_file_get_error(f);
     }
 
     DPRINTF("Completed load of VM with exit code %d seq iteration "
diff --git a/block.c b/block.c
index d3aebeb..27533f3 100644
--- a/block.c
+++ b/block.c
@@ -5043,6 +5043,11 @@ void bdrv_invalidate_cache(BlockDriverState *bs, Error **errp)
         return;
     }
 
+    if (!(bs->open_flags & BDRV_O_INCOMING)) {
+        return;
+    }
+    bs->open_flags &= ~BDRV_O_INCOMING;
+
     if (bs->drv->bdrv_invalidate_cache) {
         bs->drv->bdrv_invalidate_cache(bs, &local_err);
     } else if (bs->file) {
@@ -5078,19 +5083,6 @@ void bdrv_invalidate_cache_all(Error **errp)
     }
 }
 
-void bdrv_clear_incoming_migration_all(void)
-{
-    BlockDriverState *bs;
-
-    QTAILQ_FOREACH(bs, &bdrv_states, device_list) {
-        AioContext *aio_context = bdrv_get_aio_context(bs);
-
-        aio_context_acquire(aio_context);
-        bs->open_flags = bs->open_flags & ~(BDRV_O_INCOMING);
-        aio_context_release(aio_context);
-    }
-}
-
 int bdrv_flush(BlockDriverState *bs)
 {
     Coroutine *co;
diff --git a/include/migration/qemu-file.h b/include/migration/qemu-file.h
index c90f529..401676b 100644
--- a/include/migration/qemu-file.h
+++ b/include/migration/qemu-file.h
@@ -25,6 +25,8 @@
 #define QEMU_FILE_H 1
 #include "exec/cpu-common.h"
 
+#include <stdint.h>
+
 /* This function writes a chunk of data to a file at the given position.
  * The pos argument can be ignored if the file is only being used for
  * streaming.  The handler should try to write all of the data it can.
@@ -94,11 +96,19 @@ typedef struct QEMUFileOps {
     QEMURamSaveFunc *save_page;
 } QEMUFileOps;
 
+struct QEMUSizedBuffer {
+    struct iovec *iov;
+    size_t n_iov;
+    size_t size; /* total allocated size in all iov's */
+    size_t used; /* number of used bytes */
+};
+
 QEMUFile *qemu_fopen_ops(void *opaque, const QEMUFileOps *ops);
 QEMUFile *qemu_fopen(const char *filename, const char *mode);
 QEMUFile *qemu_fdopen(int fd, const char *mode);
 QEMUFile *qemu_fopen_socket(int fd, const char *mode);
 QEMUFile *qemu_popen_cmd(const char *command, const char *mode);
+QEMUFile *qemu_bufopen(const char *mode, QEMUSizedBuffer *input);
 int qemu_get_fd(QEMUFile *f);
 int qemu_fclose(QEMUFile *f);
 int64_t qemu_ftell(QEMUFile *f);
@@ -110,6 +120,23 @@ void qemu_put_byte(QEMUFile *f, int v);
  */
 void qemu_put_buffer_async(QEMUFile *f, const uint8_t *buf, int size);
 bool qemu_file_mode_is_not_valid(const char *mode);
+bool qemu_file_is_writable(QEMUFile *f);
+
+QEMUSizedBuffer *qsb_create(const uint8_t *buffer, size_t len);
+QEMUSizedBuffer *qsb_clone(const QEMUSizedBuffer *);
+void qsb_free(QEMUSizedBuffer *);
+size_t qsb_set_length(QEMUSizedBuffer *qsb, size_t length);
+size_t qsb_get_length(const QEMUSizedBuffer *qsb);
+ssize_t qsb_get_buffer(const QEMUSizedBuffer *, off_t start, size_t count,
+                       uint8_t *buf);
+ssize_t qsb_write_at(QEMUSizedBuffer *qsb, const uint8_t *buf,
+                     off_t pos, size_t count);
+
+
+/*
+ * For use on files opened with qemu_bufopen
+ */
+const QEMUSizedBuffer *qemu_buf_get(QEMUFile *f);
 
 static inline void qemu_put_ubyte(QEMUFile *f, unsigned int v)
 {
diff --git a/include/migration/vmstate.h b/include/migration/vmstate.h
index 9a001bd..e45fc49 100644
--- a/include/migration/vmstate.h
+++ b/include/migration/vmstate.h
@@ -484,6 +484,17 @@ extern const VMStateInfo vmstate_info_bitmap;
     .start        = (_start),                                        \
 }
 
+#define VMSTATE_VBUFFER_ALLOC_UINT32(_field, _state, _version, _test, _start, _field_size) { \
+    .name         = (stringify(_field)),                             \
+    .version_id   = (_version),                                      \
+    .field_exists = (_test),                                         \
+    .size_offset  = vmstate_offset_value(_state, _field_size, uint32_t),\
+    .info         = &vmstate_info_buffer,                            \
+    .flags        = VMS_VBUFFER|VMS_POINTER|VMS_ALLOC,               \
+    .offset       = offsetof(_state, _field),                        \
+    .start        = (_start),                                        \
+}
+
 #define VMSTATE_BUFFER_UNSAFE_INFO(_field, _state, _version, _info, _size) { \
     .name       = (stringify(_field)),                               \
     .version_id = (_version),                                        \
diff --git a/include/qemu/typedefs.h b/include/qemu/typedefs.h
index 04df51b..168a408 100644
--- a/include/qemu/typedefs.h
+++ b/include/qemu/typedefs.h
@@ -71,6 +71,7 @@ typedef struct SSIBus SSIBus;
 typedef struct EventNotifier EventNotifier;
 typedef struct VirtIODevice VirtIODevice;
 typedef struct QEMUSGList QEMUSGList;
+typedef struct QEMUSizedBuffer QEMUSizedBuffer;
 typedef struct SHPCDevice SHPCDevice;
 typedef struct FWCfgState FWCfgState;
 typedef struct PcGuestInfo PcGuestInfo;
diff --git a/migration.c b/migration.c
index 8d675b3..c49a05a 100644
--- a/migration.c
+++ b/migration.c
@@ -103,7 +103,6 @@ static void process_incoming_migration_co(void *opaque)
     }
     qemu_announce_self();
 
-    bdrv_clear_incoming_migration_all();
     /* Make sure all file formats flush their mutable metadata */
     bdrv_invalidate_cache_all(&local_err);
     if (local_err) {
diff --git a/nbd.c b/nbd.c
index e9b539b..a7bce45 100644
--- a/nbd.c
+++ b/nbd.c
@@ -972,6 +972,12 @@ NBDExport *nbd_export_new(BlockDriverState *bs, off_t dev_offset,
     exp->ctx = bdrv_get_aio_context(bs);
     bdrv_ref(bs);
     bdrv_add_aio_context_notifier(bs, bs_aio_attached, bs_aio_detach, exp);
+    /*
+     * NBD exports are used for non-shared storage migration.  Make sure
+     * that BDRV_O_INCOMING is cleared and the image is ready for write
+     * access since the export could be available before migration handover.
+     */
+    bdrv_invalidate_cache(bs, NULL);
     return exp;
 }
 
diff --git a/qemu-file-stdio.c b/qemu-file-stdio.c
new file mode 100644
index 0000000..285068b
--- /dev/null
+++ b/qemu-file-stdio.c
@@ -0,0 +1,194 @@
+/*
+ * QEMU System Emulator
+ *
+ * Copyright (c) 2003-2008 Fabrice Bellard
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
+ * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+#include "qemu-common.h"
+#include "block/coroutine.h"
+#include "migration/qemu-file.h"
+
+typedef struct QEMUFileStdio {
+    FILE *stdio_file;
+    QEMUFile *file;
+} QEMUFileStdio;
+
+static int stdio_get_fd(void *opaque)
+{
+    QEMUFileStdio *s = opaque;
+
+    return fileno(s->stdio_file);
+}
+
+static int stdio_put_buffer(void *opaque, const uint8_t *buf, int64_t pos,
+                            int size)
+{
+    QEMUFileStdio *s = opaque;
+    int res;
+
+    res = fwrite(buf, 1, size, s->stdio_file);
+
+    if (res != size) {
+        return -errno;
+    }
+    return res;
+}
+
+static int stdio_get_buffer(void *opaque, uint8_t *buf, int64_t pos, int size)
+{
+    QEMUFileStdio *s = opaque;
+    FILE *fp = s->stdio_file;
+    int bytes;
+
+    for (;;) {
+        clearerr(fp);
+        bytes = fread(buf, 1, size, fp);
+        if (bytes != 0 || !ferror(fp)) {
+            break;
+        }
+        if (errno == EAGAIN) {
+            yield_until_fd_readable(fileno(fp));
+        } else if (errno != EINTR) {
+            break;
+        }
+    }
+    return bytes;
+}
+
+static int stdio_pclose(void *opaque)
+{
+    QEMUFileStdio *s = opaque;
+    int ret;
+    ret = pclose(s->stdio_file);
+    if (ret == -1) {
+        ret = -errno;
+    } else if (!WIFEXITED(ret) || WEXITSTATUS(ret) != 0) {
+        /* close succeeded, but non-zero exit code: */
+        ret = -EIO; /* fake errno value */
+    }
+    g_free(s);
+    return ret;
+}
+
+static int stdio_fclose(void *opaque)
+{
+    QEMUFileStdio *s = opaque;
+    int ret = 0;
+
+    if (qemu_file_is_writable(s->file)) {
+        int fd = fileno(s->stdio_file);
+        struct stat st;
+
+        ret = fstat(fd, &st);
+        if (ret == 0 && S_ISREG(st.st_mode)) {
+            /*
+             * If the file handle is a regular file make sure the
+             * data is flushed to disk before signaling success.
+             */
+            ret = fsync(fd);
+            if (ret != 0) {
+                ret = -errno;
+                return ret;
+            }
+        }
+    }
+    if (fclose(s->stdio_file) == EOF) {
+        ret = -errno;
+    }
+    g_free(s);
+    return ret;
+}
+
+static const QEMUFileOps stdio_pipe_read_ops = {
+    .get_fd =     stdio_get_fd,
+    .get_buffer = stdio_get_buffer,
+    .close =      stdio_pclose
+};
+
+static const QEMUFileOps stdio_pipe_write_ops = {
+    .get_fd =     stdio_get_fd,
+    .put_buffer = stdio_put_buffer,
+    .close =      stdio_pclose
+};
+
+QEMUFile *qemu_popen_cmd(const char *command, const char *mode)
+{
+    FILE *stdio_file;
+    QEMUFileStdio *s;
+
+    if (mode == NULL || (mode[0] != 'r' && mode[0] != 'w') || mode[1] != 0) {
+        fprintf(stderr, "qemu_popen: Argument validity check failed\n");
+        return NULL;
+    }
+
+    stdio_file = popen(command, mode);
+    if (stdio_file == NULL) {
+        return NULL;
+    }
+
+    s = g_malloc0(sizeof(QEMUFileStdio));
+
+    s->stdio_file = stdio_file;
+
+    if (mode[0] == 'r') {
+        s->file = qemu_fopen_ops(s, &stdio_pipe_read_ops);
+    } else {
+        s->file = qemu_fopen_ops(s, &stdio_pipe_write_ops);
+    }
+    return s->file;
+}
+
+static const QEMUFileOps stdio_file_read_ops = {
+    .get_fd =     stdio_get_fd,
+    .get_buffer = stdio_get_buffer,
+    .close =      stdio_fclose
+};
+
+static const QEMUFileOps stdio_file_write_ops = {
+    .get_fd =     stdio_get_fd,
+    .put_buffer = stdio_put_buffer,
+    .close =      stdio_fclose
+};
+
+QEMUFile *qemu_fopen(const char *filename, const char *mode)
+{
+    QEMUFileStdio *s;
+
+    if (qemu_file_mode_is_not_valid(mode)) {
+        return NULL;
+    }
+
+    s = g_malloc0(sizeof(QEMUFileStdio));
+
+    s->stdio_file = fopen(filename, mode);
+    if (!s->stdio_file) {
+        goto fail;
+    }
+
+    if (mode[0] == 'w') {
+        s->file = qemu_fopen_ops(s, &stdio_file_write_ops);
+    } else {
+        s->file = qemu_fopen_ops(s, &stdio_file_read_ops);
+    }
+    return s->file;
+fail:
+    g_free(s);
+    return NULL;
+}
diff --git a/qemu-file-unix.c b/qemu-file-unix.c
new file mode 100644
index 0000000..9682396
--- /dev/null
+++ b/qemu-file-unix.c
@@ -0,0 +1,223 @@
+/*
+ * QEMU System Emulator
+ *
+ * Copyright (c) 2003-2008 Fabrice Bellard
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
+ * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+#include "qemu-common.h"
+#include "qemu/iov.h"
+#include "qemu/sockets.h"
+#include "block/coroutine.h"
+#include "migration/qemu-file.h"
+
+typedef struct QEMUFileSocket {
+    int fd;
+    QEMUFile *file;
+} QEMUFileSocket;
+
+static ssize_t socket_writev_buffer(void *opaque, struct iovec *iov, int iovcnt,
+                                    int64_t pos)
+{
+    QEMUFileSocket *s = opaque;
+    ssize_t len;
+    ssize_t size = iov_size(iov, iovcnt);
+
+    len = iov_send(s->fd, iov, iovcnt, 0, size);
+    if (len < size) {
+        len = -socket_error();
+    }
+    return len;
+}
+
+static int socket_get_fd(void *opaque)
+{
+    QEMUFileSocket *s = opaque;
+
+    return s->fd;
+}
+
+static int socket_get_buffer(void *opaque, uint8_t *buf, int64_t pos, int size)
+{
+    QEMUFileSocket *s = opaque;
+    ssize_t len;
+
+    for (;;) {
+        len = qemu_recv(s->fd, buf, size, 0);
+        if (len != -1) {
+            break;
+        }
+        if (socket_error() == EAGAIN) {
+            yield_until_fd_readable(s->fd);
+        } else if (socket_error() != EINTR) {
+            break;
+        }
+    }
+
+    if (len == -1) {
+        len = -socket_error();
+    }
+    return len;
+}
+
+static int socket_close(void *opaque)
+{
+    QEMUFileSocket *s = opaque;
+    closesocket(s->fd);
+    g_free(s);
+    return 0;
+}
+
+static ssize_t unix_writev_buffer(void *opaque, struct iovec *iov, int iovcnt,
+                                  int64_t pos)
+{
+    QEMUFileSocket *s = opaque;
+    ssize_t len, offset;
+    ssize_t size = iov_size(iov, iovcnt);
+    ssize_t total = 0;
+
+    assert(iovcnt > 0);
+    offset = 0;
+    while (size > 0) {
+        /* Find the next start position; skip all full-sized vector elements  */
+        while (offset >= iov[0].iov_len) {
+            offset -= iov[0].iov_len;
+            iov++, iovcnt--;
+        }
+
+        /* skip `offset' bytes from the (now) first element, undo it on exit */
+        assert(iovcnt > 0);
+        iov[0].iov_base += offset;
+        iov[0].iov_len -= offset;
+
+        do {
+            len = writev(s->fd, iov, iovcnt);
+        } while (len == -1 && errno == EINTR);
+        if (len == -1) {
+            return -errno;
+        }
+
+        /* Undo the changes above */
+        iov[0].iov_base -= offset;
+        iov[0].iov_len += offset;
+
+        /* Prepare for the next iteration */
+        offset += len;
+        total += len;
+        size -= len;
+    }
+
+    return total;
+}
+
+static int unix_get_buffer(void *opaque, uint8_t *buf, int64_t pos, int size)
+{
+    QEMUFileSocket *s = opaque;
+    ssize_t len;
+
+    for (;;) {
+        len = read(s->fd, buf, size);
+        if (len != -1) {
+            break;
+        }
+        if (errno == EAGAIN) {
+            yield_until_fd_readable(s->fd);
+        } else if (errno != EINTR) {
+            break;
+        }
+    }
+
+    if (len == -1) {
+        len = -errno;
+    }
+    return len;
+}
+
+static int unix_close(void *opaque)
+{
+    QEMUFileSocket *s = opaque;
+    close(s->fd);
+    g_free(s);
+    return 0;
+}
+
+static const QEMUFileOps unix_read_ops = {
+    .get_fd =     socket_get_fd,
+    .get_buffer = unix_get_buffer,
+    .close =      unix_close
+};
+
+static const QEMUFileOps unix_write_ops = {
+    .get_fd =     socket_get_fd,
+    .writev_buffer = unix_writev_buffer,
+    .close =      unix_close
+};
+
+QEMUFile *qemu_fdopen(int fd, const char *mode)
+{
+    QEMUFileSocket *s;
+
+    if (mode == NULL ||
+        (mode[0] != 'r' && mode[0] != 'w') ||
+        mode[1] != 'b' || mode[2] != 0) {
+        fprintf(stderr, "qemu_fdopen: Argument validity check failed\n");
+        return NULL;
+    }
+
+    s = g_malloc0(sizeof(QEMUFileSocket));
+    s->fd = fd;
+
+    if (mode[0] == 'r') {
+        s->file = qemu_fopen_ops(s, &unix_read_ops);
+    } else {
+        s->file = qemu_fopen_ops(s, &unix_write_ops);
+    }
+    return s->file;
+}
+
+static const QEMUFileOps socket_read_ops = {
+    .get_fd =     socket_get_fd,
+    .get_buffer = socket_get_buffer,
+    .close =      socket_close
+};
+
+static const QEMUFileOps socket_write_ops = {
+    .get_fd =     socket_get_fd,
+    .writev_buffer = socket_writev_buffer,
+    .close =      socket_close
+};
+
+QEMUFile *qemu_fopen_socket(int fd, const char *mode)
+{
+    QEMUFileSocket *s;
+
+    if (qemu_file_mode_is_not_valid(mode)) {
+        return NULL;
+    }
+
+    s = g_malloc0(sizeof(QEMUFileSocket));
+    s->fd = fd;
+    if (mode[0] == 'w') {
+        qemu_set_block(s->fd);
+        s->file = qemu_fopen_ops(s, &socket_write_ops);
+    } else {
+        s->file = qemu_fopen_ops(s, &socket_read_ops);
+    }
+    return s->file;
+}
diff --git a/qemu-file.c b/qemu-file.c
index a8e3912..f938e36 100644
--- a/qemu-file.c
+++ b/qemu-file.c
@@ -1,3 +1,26 @@
+/*
+ * QEMU System Emulator
+ *
+ * Copyright (c) 2003-2008 Fabrice Bellard
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
+ * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
 #include "qemu-common.h"
 #include "qemu/iov.h"
 #include "qemu/sockets.h"
@@ -28,324 +51,6 @@ struct QEMUFile {
     int last_error;
 };
 
-typedef struct QEMUFileStdio {
-    FILE *stdio_file;
-    QEMUFile *file;
-} QEMUFileStdio;
-
-typedef struct QEMUFileSocket {
-    int fd;
-    QEMUFile *file;
-} QEMUFileSocket;
-
-static ssize_t socket_writev_buffer(void *opaque, struct iovec *iov, int iovcnt,
-                                    int64_t pos)
-{
-    QEMUFileSocket *s = opaque;
-    ssize_t len;
-    ssize_t size = iov_size(iov, iovcnt);
-
-    len = iov_send(s->fd, iov, iovcnt, 0, size);
-    if (len < size) {
-        len = -socket_error();
-    }
-    return len;
-}
-
-static int socket_get_fd(void *opaque)
-{
-    QEMUFileSocket *s = opaque;
-
-    return s->fd;
-}
-
-static int socket_get_buffer(void *opaque, uint8_t *buf, int64_t pos, int size)
-{
-    QEMUFileSocket *s = opaque;
-    ssize_t len;
-
-    for (;;) {
-        len = qemu_recv(s->fd, buf, size, 0);
-        if (len != -1) {
-            break;
-        }
-        if (socket_error() == EAGAIN) {
-            yield_until_fd_readable(s->fd);
-        } else if (socket_error() != EINTR) {
-            break;
-        }
-    }
-
-    if (len == -1) {
-        len = -socket_error();
-    }
-    return len;
-}
-
-static int socket_close(void *opaque)
-{
-    QEMUFileSocket *s = opaque;
-    closesocket(s->fd);
-    g_free(s);
-    return 0;
-}
-
-static int stdio_get_fd(void *opaque)
-{
-    QEMUFileStdio *s = opaque;
-
-    return fileno(s->stdio_file);
-}
-
-static int stdio_put_buffer(void *opaque, const uint8_t *buf, int64_t pos,
-                            int size)
-{
-    QEMUFileStdio *s = opaque;
-    int res;
-
-    res = fwrite(buf, 1, size, s->stdio_file);
-
-    if (res != size) {
-        return -errno;
-    }
-    return res;
-}
-
-static int stdio_get_buffer(void *opaque, uint8_t *buf, int64_t pos, int size)
-{
-    QEMUFileStdio *s = opaque;
-    FILE *fp = s->stdio_file;
-    int bytes;
-
-    for (;;) {
-        clearerr(fp);
-        bytes = fread(buf, 1, size, fp);
-        if (bytes != 0 || !ferror(fp)) {
-            break;
-        }
-        if (errno == EAGAIN) {
-            yield_until_fd_readable(fileno(fp));
-        } else if (errno != EINTR) {
-            break;
-        }
-    }
-    return bytes;
-}
-
-static int stdio_pclose(void *opaque)
-{
-    QEMUFileStdio *s = opaque;
-    int ret;
-    ret = pclose(s->stdio_file);
-    if (ret == -1) {
-        ret = -errno;
-    } else if (!WIFEXITED(ret) || WEXITSTATUS(ret) != 0) {
-        /* close succeeded, but non-zero exit code: */
-        ret = -EIO; /* fake errno value */
-    }
-    g_free(s);
-    return ret;
-}
-
-static int stdio_fclose(void *opaque)
-{
-    QEMUFileStdio *s = opaque;
-    int ret = 0;
-
-    if (s->file->ops->put_buffer || s->file->ops->writev_buffer) {
-        int fd = fileno(s->stdio_file);
-        struct stat st;
-
-        ret = fstat(fd, &st);
-        if (ret == 0 && S_ISREG(st.st_mode)) {
-            /*
-             * If the file handle is a regular file make sure the
-             * data is flushed to disk before signaling success.
-             */
-            ret = fsync(fd);
-            if (ret != 0) {
-                ret = -errno;
-                return ret;
-            }
-        }
-    }
-    if (fclose(s->stdio_file) == EOF) {
-        ret = -errno;
-    }
-    g_free(s);
-    return ret;
-}
-
-static const QEMUFileOps stdio_pipe_read_ops = {
-    .get_fd =     stdio_get_fd,
-    .get_buffer = stdio_get_buffer,
-    .close =      stdio_pclose
-};
-
-static const QEMUFileOps stdio_pipe_write_ops = {
-    .get_fd =     stdio_get_fd,
-    .put_buffer = stdio_put_buffer,
-    .close =      stdio_pclose
-};
-
-QEMUFile *qemu_popen_cmd(const char *command, const char *mode)
-{
-    FILE *stdio_file;
-    QEMUFileStdio *s;
-
-    if (mode == NULL || (mode[0] != 'r' && mode[0] != 'w') || mode[1] != 0) {
-        fprintf(stderr, "qemu_popen: Argument validity check failed\n");
-        return NULL;
-    }
-
-    stdio_file = popen(command, mode);
-    if (stdio_file == NULL) {
-        return NULL;
-    }
-
-    s = g_malloc0(sizeof(QEMUFileStdio));
-
-    s->stdio_file = stdio_file;
-
-    if (mode[0] == 'r') {
-        s->file = qemu_fopen_ops(s, &stdio_pipe_read_ops);
-    } else {
-        s->file = qemu_fopen_ops(s, &stdio_pipe_write_ops);
-    }
-    return s->file;
-}
-
-static const QEMUFileOps stdio_file_read_ops = {
-    .get_fd =     stdio_get_fd,
-    .get_buffer = stdio_get_buffer,
-    .close =      stdio_fclose
-};
-
-static const QEMUFileOps stdio_file_write_ops = {
-    .get_fd =     stdio_get_fd,
-    .put_buffer = stdio_put_buffer,
-    .close =      stdio_fclose
-};
-
-static ssize_t unix_writev_buffer(void *opaque, struct iovec *iov, int iovcnt,
-                                  int64_t pos)
-{
-    QEMUFileSocket *s = opaque;
-    ssize_t len, offset;
-    ssize_t size = iov_size(iov, iovcnt);
-    ssize_t total = 0;
-
-    assert(iovcnt > 0);
-    offset = 0;
-    while (size > 0) {
-        /* Find the next start position; skip all full-sized vector elements  */
-        while (offset >= iov[0].iov_len) {
-            offset -= iov[0].iov_len;
-            iov++, iovcnt--;
-        }
-
-        /* skip `offset' bytes from the (now) first element, undo it on exit */
-        assert(iovcnt > 0);
-        iov[0].iov_base += offset;
-        iov[0].iov_len -= offset;
-
-        do {
-            len = writev(s->fd, iov, iovcnt);
-        } while (len == -1 && errno == EINTR);
-        if (len == -1) {
-            return -errno;
-        }
-
-        /* Undo the changes above */
-        iov[0].iov_base -= offset;
-        iov[0].iov_len += offset;
-
-        /* Prepare for the next iteration */
-        offset += len;
-        total += len;
-        size -= len;
-    }
-
-    return total;
-}
-
-static int unix_get_buffer(void *opaque, uint8_t *buf, int64_t pos, int size)
-{
-    QEMUFileSocket *s = opaque;
-    ssize_t len;
-
-    for (;;) {
-        len = read(s->fd, buf, size);
-        if (len != -1) {
-            break;
-        }
-        if (errno == EAGAIN) {
-            yield_until_fd_readable(s->fd);
-        } else if (errno != EINTR) {
-            break;
-        }
-    }
-
-    if (len == -1) {
-        len = -errno;
-    }
-    return len;
-}
-
-static int unix_close(void *opaque)
-{
-    QEMUFileSocket *s = opaque;
-    close(s->fd);
-    g_free(s);
-    return 0;
-}
-
-static const QEMUFileOps unix_read_ops = {
-    .get_fd =     socket_get_fd,
-    .get_buffer = unix_get_buffer,
-    .close =      unix_close
-};
-
-static const QEMUFileOps unix_write_ops = {
-    .get_fd =     socket_get_fd,
-    .writev_buffer = unix_writev_buffer,
-    .close =      unix_close
-};
-
-QEMUFile *qemu_fdopen(int fd, const char *mode)
-{
-    QEMUFileSocket *s;
-
-    if (mode == NULL ||
-        (mode[0] != 'r' && mode[0] != 'w') ||
-        mode[1] != 'b' || mode[2] != 0) {
-        fprintf(stderr, "qemu_fdopen: Argument validity check failed\n");
-        return NULL;
-    }
-
-    s = g_malloc0(sizeof(QEMUFileSocket));
-    s->fd = fd;
-
-    if (mode[0] == 'r') {
-        s->file = qemu_fopen_ops(s, &unix_read_ops);
-    } else {
-        s->file = qemu_fopen_ops(s, &unix_write_ops);
-    }
-    return s->file;
-}
-
-static const QEMUFileOps socket_read_ops = {
-    .get_fd =     socket_get_fd,
-    .get_buffer = socket_get_buffer,
-    .close =      socket_close
-};
-
-static const QEMUFileOps socket_write_ops = {
-    .get_fd =     socket_get_fd,
-    .writev_buffer = socket_writev_buffer,
-    .close =      socket_close
-};
-
 bool qemu_file_mode_is_not_valid(const char *mode)
 {
     if (mode == NULL ||
@@ -358,51 +63,6 @@ bool qemu_file_mode_is_not_valid(const char *mode)
     return false;
 }
 
-QEMUFile *qemu_fopen_socket(int fd, const char *mode)
-{
-    QEMUFileSocket *s;
-
-    if (qemu_file_mode_is_not_valid(mode)) {
-        return NULL;
-    }
-
-    s = g_malloc0(sizeof(QEMUFileSocket));
-    s->fd = fd;
-    if (mode[0] == 'w') {
-        qemu_set_block(s->fd);
-        s->file = qemu_fopen_ops(s, &socket_write_ops);
-    } else {
-        s->file = qemu_fopen_ops(s, &socket_read_ops);
-    }
-    return s->file;
-}
-
-QEMUFile *qemu_fopen(const char *filename, const char *mode)
-{
-    QEMUFileStdio *s;
-
-    if (qemu_file_mode_is_not_valid(mode)) {
-        return NULL;
-    }
-
-    s = g_malloc0(sizeof(QEMUFileStdio));
-
-    s->stdio_file = fopen(filename, mode);
-    if (!s->stdio_file) {
-        goto fail;
-    }
-
-    if (mode[0] == 'w') {
-        s->file = qemu_fopen_ops(s, &stdio_file_write_ops);
-    } else {
-        s->file = qemu_fopen_ops(s, &stdio_file_read_ops);
-    }
-    return s->file;
-fail:
-    g_free(s);
-    return NULL;
-}
-
 QEMUFile *qemu_fopen_ops(void *opaque, const QEMUFileOps *ops)
 {
     QEMUFile *f;
@@ -433,7 +93,7 @@ void qemu_file_set_error(QEMUFile *f, int ret)
     }
 }
 
-static inline bool qemu_file_is_writable(QEMUFile *f)
+bool qemu_file_is_writable(QEMUFile *f)
 {
     return f->ops->writev_buffer || f->ops->put_buffer;
 }
@@ -878,3 +538,458 @@ uint64_t qemu_get_be64(QEMUFile *f)
     v |= qemu_get_be32(f);
     return v;
 }
+
+#define QSB_CHUNK_SIZE      (1 << 10)
+#define QSB_MAX_CHUNK_SIZE  (16 * QSB_CHUNK_SIZE)
+
+/**
+ * Create a QEMUSizedBuffer
+ * This type of buffer uses scatter-gather lists internally and
+ * can grow to any size. Any data array in the scatter-gather list
+ * can hold different amount of bytes.
+ *
+ * @buffer: Optional buffer to copy into the QSB
+ * @len: size of initial buffer; if @buffer is given, buffer must
+ *       hold at least len bytes
+ *
+ * Returns a pointer to a QEMUSizedBuffer or NULL on allocation failure
+ */
+QEMUSizedBuffer *qsb_create(const uint8_t *buffer, size_t len)
+{
+    QEMUSizedBuffer *qsb;
+    size_t alloc_len, num_chunks, i, to_copy;
+    size_t chunk_size = (len > QSB_MAX_CHUNK_SIZE)
+                        ? QSB_MAX_CHUNK_SIZE
+                        : QSB_CHUNK_SIZE;
+
+    num_chunks = DIV_ROUND_UP(len ? len : QSB_CHUNK_SIZE, chunk_size);
+    alloc_len = num_chunks * chunk_size;
+
+    qsb = g_try_new0(QEMUSizedBuffer, 1);
+    if (!qsb) {
+        return NULL;
+    }
+
+    qsb->iov = g_try_new0(struct iovec, num_chunks);
+    if (!qsb->iov) {
+        g_free(qsb);
+        return NULL;
+    }
+
+    qsb->n_iov = num_chunks;
+
+    for (i = 0; i < num_chunks; i++) {
+        qsb->iov[i].iov_base = g_try_malloc0(chunk_size);
+        if (!qsb->iov[i].iov_base) {
+            /* qsb_free is safe since g_free can cope with NULL */
+            qsb_free(qsb);
+            return NULL;
+        }
+
+        qsb->iov[i].iov_len = chunk_size;
+        if (buffer) {
+            to_copy = (len - qsb->used) > chunk_size
+                      ? chunk_size : (len - qsb->used);
+            memcpy(qsb->iov[i].iov_base, &buffer[qsb->used], to_copy);
+            qsb->used += to_copy;
+        }
+    }
+
+    qsb->size = alloc_len;
+
+    return qsb;
+}
+
+/**
+ * Free the QEMUSizedBuffer
+ *
+ * @qsb: The QEMUSizedBuffer to free
+ */
+void qsb_free(QEMUSizedBuffer *qsb)
+{
+    size_t i;
+
+    if (!qsb) {
+        return;
+    }
+
+    for (i = 0; i < qsb->n_iov; i++) {
+        g_free(qsb->iov[i].iov_base);
+    }
+    g_free(qsb->iov);
+    g_free(qsb);
+}
+
+/**
+ * Get the number of used bytes in the QEMUSizedBuffer
+ *
+ * @qsb: A QEMUSizedBuffer
+ *
+ * Returns the number of bytes currently used in this buffer
+ */
+size_t qsb_get_length(const QEMUSizedBuffer *qsb)
+{
+    return qsb->used;
+}
+
+/**
+ * Set the length of the buffer; the primary usage of this
+ * function is to truncate the number of used bytes in the buffer.
+ * The size will not be extended beyond the current number of
+ * allocated bytes in the QEMUSizedBuffer.
+ *
+ * @qsb: A QEMUSizedBuffer
+ * @new_len: The new length of bytes in the buffer
+ *
+ * Returns the number of bytes the buffer was truncated or extended
+ * to.
+ */
+size_t qsb_set_length(QEMUSizedBuffer *qsb, size_t new_len)
+{
+    if (new_len <= qsb->size) {
+        qsb->used = new_len;
+    } else {
+        qsb->used = qsb->size;
+    }
+    return qsb->used;
+}
+
+/**
+ * Get the iovec that holds the data for a given position @pos.
+ *
+ * @qsb: A QEMUSizedBuffer
+ * @pos: The index of a byte in the buffer
+ * @d_off: Pointer to an offset that this function will indicate
+ *         at what position within the returned iovec the byte
+ *         is to be found
+ *
+ * Returns the index of the iovec that holds the byte at the given
+ * index @pos in the byte stream; a negative number if the iovec
+ * for the given position @pos does not exist.
+ */
+static ssize_t qsb_get_iovec(const QEMUSizedBuffer *qsb,
+                             off_t pos, off_t *d_off)
+{
+    ssize_t i;
+    off_t curr = 0;
+
+    if (pos > qsb->used) {
+        return -1;
+    }
+
+    for (i = 0; i < qsb->n_iov; i++) {
+        if (curr + qsb->iov[i].iov_len > pos) {
+            *d_off = pos - curr;
+            return i;
+        }
+        curr += qsb->iov[i].iov_len;
+    }
+    return -1;
+}
+
+/*
+ * Convert the QEMUSizedBuffer into a flat buffer.
+ *
+ * Note: If at all possible, try to avoid this function since it
+ *       may unnecessarily copy memory around.
+ *
+ * @qsb: pointer to QEMUSizedBuffer
+ * @start: offset to start at
+ * @count: number of bytes to copy
+ * @buf: a pointer to a buffer to write into (at least @count bytes)
+ *
+ * Returns the number of bytes copied into the output buffer
+ */
+ssize_t qsb_get_buffer(const QEMUSizedBuffer *qsb, off_t start,
+                       size_t count, uint8_t *buffer)
+{
+    const struct iovec *iov;
+    size_t to_copy, all_copy;
+    ssize_t index;
+    off_t s_off;
+    off_t d_off = 0;
+    char *s;
+
+    if (start > qsb->used) {
+        return 0;
+    }
+
+    all_copy = qsb->used - start;
+    if (all_copy > count) {
+        all_copy = count;
+    } else {
+        count = all_copy;
+    }
+
+    index = qsb_get_iovec(qsb, start, &s_off);
+    if (index < 0) {
+        return 0;
+    }
+
+    while (all_copy > 0) {
+        iov = &qsb->iov[index];
+
+        s = iov->iov_base;
+
+        to_copy = iov->iov_len - s_off;
+        if (to_copy > all_copy) {
+            to_copy = all_copy;
+        }
+        memcpy(&buffer[d_off], &s[s_off], to_copy);
+
+        d_off += to_copy;
+        all_copy -= to_copy;
+
+        s_off = 0;
+        index++;
+    }
+
+    return count;
+}
+
+/**
+ * Grow the QEMUSizedBuffer to the given size and allocate
+ * memory for it.
+ *
+ * @qsb: A QEMUSizedBuffer
+ * @new_size: The new size of the buffer
+ *
+ * Return:
+ *    a negative error code in case of memory allocation failure
+ * or
+ *    the new size of the buffer. The returned size may be greater or equal
+ *    to @new_size.
+ */
+static ssize_t qsb_grow(QEMUSizedBuffer *qsb, size_t new_size)
+{
+    size_t needed_chunks, i;
+
+    if (qsb->size < new_size) {
+        struct iovec *new_iov;
+        size_t size_diff = new_size - qsb->size;
+        size_t chunk_size = (size_diff > QSB_MAX_CHUNK_SIZE)
+                             ? QSB_MAX_CHUNK_SIZE : QSB_CHUNK_SIZE;
+
+        needed_chunks = DIV_ROUND_UP(size_diff, chunk_size);
+
+        new_iov = g_try_new(struct iovec, qsb->n_iov + needed_chunks);
+        if (new_iov == NULL) {
+            return -ENOMEM;
+        }
+
+        /* Allocate new chunks as needed into new_iov */
+        for (i = qsb->n_iov; i < qsb->n_iov + needed_chunks; i++) {
+            new_iov[i].iov_base = g_try_malloc0(chunk_size);
+            new_iov[i].iov_len = chunk_size;
+            if (!new_iov[i].iov_base) {
+                size_t j;
+
+                /* Free previously allocated new chunks */
+                for (j = qsb->n_iov; j < i; j++) {
+                    g_free(new_iov[j].iov_base);
+                }
+                g_free(new_iov);
+
+                return -ENOMEM;
+            }
+        }
+
+        /*
+         * Now we can't get any allocation errors, copy over to new iov
+         * and switch.
+         */
+        for (i = 0; i < qsb->n_iov; i++) {
+            new_iov[i] = qsb->iov[i];
+        }
+
+        qsb->n_iov += needed_chunks;
+        g_free(qsb->iov);
+        qsb->iov = new_iov;
+        qsb->size += (needed_chunks * chunk_size);
+    }
+
+    return qsb->size;
+}
+
+/**
+ * Write into the QEMUSizedBuffer at a given position and a given
+ * number of bytes. This function will automatically grow the
+ * QEMUSizedBuffer.
+ *
+ * @qsb: A QEMUSizedBuffer
+ * @source: A byte array to copy data from
+ * @pos: The position within the @qsb to write data to
+ * @size: The number of bytes to copy into the @qsb
+ *
+ * Returns @size or a negative error code in case of memory allocation failure,
+ *           or with an invalid 'pos'
+ */
+ssize_t qsb_write_at(QEMUSizedBuffer *qsb, const uint8_t *source,
+                     off_t pos, size_t count)
+{
+    ssize_t rc = qsb_grow(qsb, pos + count);
+    size_t to_copy;
+    size_t all_copy = count;
+    const struct iovec *iov;
+    ssize_t index;
+    char *dest;
+    off_t d_off, s_off = 0;
+
+    if (rc < 0) {
+        return rc;
+    }
+
+    if (pos + count > qsb->used) {
+        qsb->used = pos + count;
+    }
+
+    index = qsb_get_iovec(qsb, pos, &d_off);
+    if (index < 0) {
+        return -EINVAL;
+    }
+
+    while (all_copy > 0) {
+        iov = &qsb->iov[index];
+
+        dest = iov->iov_base;
+
+        to_copy = iov->iov_len - d_off;
+        if (to_copy > all_copy) {
+            to_copy = all_copy;
+        }
+
+        memcpy(&dest[d_off], &source[s_off], to_copy);
+
+        s_off += to_copy;
+        all_copy -= to_copy;
+
+        d_off = 0;
+        index++;
+    }
+
+    return count;
+}
+
+/**
+ * Create a deep copy of the given QEMUSizedBuffer.
+ *
+ * @qsb: A QEMUSizedBuffer
+ *
+ * Returns a clone of @qsb or NULL on allocation failure
+ */
+QEMUSizedBuffer *qsb_clone(const QEMUSizedBuffer *qsb)
+{
+    QEMUSizedBuffer *out = qsb_create(NULL, qsb_get_length(qsb));
+    size_t i;
+    ssize_t res;
+    off_t pos = 0;
+
+    if (!out) {
+        return NULL;
+    }
+
+    for (i = 0; i < qsb->n_iov; i++) {
+        res =  qsb_write_at(out, qsb->iov[i].iov_base,
+                            pos, qsb->iov[i].iov_len);
+        if (res < 0) {
+            qsb_free(out);
+            return NULL;
+        }
+        pos += res;
+    }
+
+    return out;
+}
+
+typedef struct QEMUBuffer {
+    QEMUSizedBuffer *qsb;
+    QEMUFile *file;
+} QEMUBuffer;
+
+static int buf_get_buffer(void *opaque, uint8_t *buf, int64_t pos, int size)
+{
+    QEMUBuffer *s = opaque;
+    ssize_t len = qsb_get_length(s->qsb) - pos;
+
+    if (len <= 0) {
+        return 0;
+    }
+
+    if (len > size) {
+        len = size;
+    }
+    return qsb_get_buffer(s->qsb, pos, len, buf);
+}
+
+static int buf_put_buffer(void *opaque, const uint8_t *buf,
+                          int64_t pos, int size)
+{
+    QEMUBuffer *s = opaque;
+
+    return qsb_write_at(s->qsb, buf, pos, size);
+}
+
+static int buf_close(void *opaque)
+{
+    QEMUBuffer *s = opaque;
+
+    qsb_free(s->qsb);
+
+    g_free(s);
+
+    return 0;
+}
+
+const QEMUSizedBuffer *qemu_buf_get(QEMUFile *f)
+{
+    QEMUBuffer *p;
+
+    qemu_fflush(f);
+
+    p = f->opaque;
+
+    return p->qsb;
+}
+
+static const QEMUFileOps buf_read_ops = {
+    .get_buffer = buf_get_buffer,
+    .close =      buf_close,
+};
+
+static const QEMUFileOps buf_write_ops = {
+    .put_buffer = buf_put_buffer,
+    .close =      buf_close,
+};
+
+QEMUFile *qemu_bufopen(const char *mode, QEMUSizedBuffer *input)
+{
+    QEMUBuffer *s;
+
+    if (mode == NULL || (mode[0] != 'r' && mode[0] != 'w') ||
+        mode[1] != '\0') {
+        error_report("qemu_bufopen: Argument validity check failed");
+        return NULL;
+    }
+
+    s = g_malloc0(sizeof(QEMUBuffer));
+    if (mode[0] == 'r') {
+        s->qsb = input;
+    }
+
+    if (s->qsb == NULL) {
+        s->qsb = qsb_create(NULL, 0);
+    }
+    if (!s->qsb) {
+        g_free(s);
+        error_report("qemu_bufopen: qsb_create failed");
+        return NULL;
+    }
+
+
+    if (mode[0] == 'r') {
+        s->file = qemu_fopen_ops(s, &buf_read_ops);
+    } else {
+        s->file = qemu_fopen_ops(s, &buf_write_ops);
+    }
+    return s->file;
+}
diff --git a/tests/Makefile b/tests/Makefile
index 95deff0..16f0e4c 100644
--- a/tests/Makefile
+++ b/tests/Makefile
@@ -258,8 +258,8 @@ tests/test-qdev-global-props$(EXESUF): tests/test-qdev-global-props.o \
 	$(test-qapi-obj-y) \
 	libqemuutil.a libqemustub.a
 tests/test-vmstate$(EXESUF): tests/test-vmstate.o \
-	vmstate.o qemu-file.o \
-	libqemuutil.a
+	vmstate.o qemu-file.o qemu-file-unix.o \
+	libqemuutil.a libqemustub.a
 
 tests/test-qapi-types.c tests/test-qapi-types.h :\
 $(SRC_PATH)/tests/qapi-schema/qapi-schema-test.json $(SRC_PATH)/scripts/qapi-types.py
diff --git a/tests/test-vmstate.c b/tests/test-vmstate.c
index d72c64c..5e0fd13 100644
--- a/tests/test-vmstate.c
+++ b/tests/test-vmstate.c
@@ -43,6 +43,12 @@ void yield_until_fd_readable(int fd)
     select(fd + 1, &fds, NULL, NULL, NULL);
 }
 
+/*
+ * Some tests use 'open_test_file' to work on a real fd, some use
+ * an in memory file (QEMUSizedBuffer+qemu_bufopen); we could pick one
+ * but this way we test both.
+ */
+
 /* Duplicate temp_fd and seek to the beginning of the file */
 static QEMUFile *open_test_file(bool write)
 {
@@ -54,6 +60,30 @@ static QEMUFile *open_test_file(bool write)
     return qemu_fdopen(fd, write ? "wb" : "rb");
 }
 
+/* Open a read-only qemu-file from an existing memory block */
+static QEMUFile *open_mem_file_read(const void *data, size_t len)
+{
+    /* The qsb gets freed by qemu_fclose */
+    QEMUSizedBuffer *qsb = qsb_create(data, len);
+    g_assert(qsb);
+
+    return qemu_bufopen("r", qsb);
+}
+
+/*
+ * Check that the contents of the memory-buffered file f match
+ * the given size/data.
+ */
+static void check_mem_file(QEMUFile *f, void *data, size_t size)
+{
+    uint8_t *result = g_malloc(size);
+    const QEMUSizedBuffer *qsb = qemu_buf_get(f);
+    g_assert_cmpint(qsb_get_length(qsb), ==, size);
+    g_assert_cmpint(qsb_get_buffer(qsb, 0, size, result), ==, size);
+    g_assert_cmpint(memcmp(result, data, size), ==, 0);
+    g_free(result);
+}
+
 #define SUCCESS(val) \
     g_assert_cmpint((val), ==, 0)
 
@@ -371,14 +401,12 @@ static const VMStateDescription vmstate_skipping = {
 
 static void test_save_noskip(void)
 {
-    QEMUFile *fsave = open_test_file(true);
+    QEMUFile *fsave = qemu_bufopen("w", NULL);
     TestStruct obj = { .a = 1, .b = 2, .c = 3, .d = 4, .e = 5, .f = 6,
                        .skip_c_e = false };
     vmstate_save_state(fsave, &vmstate_skipping, &obj);
     g_assert(!qemu_file_get_error(fsave));
-    qemu_fclose(fsave);
 
-    QEMUFile *loading = open_test_file(false);
     uint8_t expected[] = {
         0, 0, 0, 1,             /* a */
         0, 0, 0, 2,             /* b */
@@ -387,52 +415,31 @@ static void test_save_noskip(void)
         0, 0, 0, 5,             /* e */
         0, 0, 0, 0, 0, 0, 0, 6, /* f */
     };
-    uint8_t result[sizeof(expected)];
-    g_assert_cmpint(qemu_get_buffer(loading, result, sizeof(result)), ==,
-                    sizeof(result));
-    g_assert(!qemu_file_get_error(loading));
-    g_assert_cmpint(memcmp(result, expected, sizeof(result)), ==, 0);
-
-    /* Must reach EOF */
-    qemu_get_byte(loading);
-    g_assert_cmpint(qemu_file_get_error(loading), ==, -EIO);
-
-    qemu_fclose(loading);
+    check_mem_file(fsave, expected, sizeof(expected));
+    qemu_fclose(fsave);
 }
 
 static void test_save_skip(void)
 {
-    QEMUFile *fsave = open_test_file(true);
+    QEMUFile *fsave = qemu_bufopen("w", NULL);
     TestStruct obj = { .a = 1, .b = 2, .c = 3, .d = 4, .e = 5, .f = 6,
                        .skip_c_e = true };
     vmstate_save_state(fsave, &vmstate_skipping, &obj);
     g_assert(!qemu_file_get_error(fsave));
-    qemu_fclose(fsave);
 
-    QEMUFile *loading = open_test_file(false);
     uint8_t expected[] = {
         0, 0, 0, 1,             /* a */
         0, 0, 0, 2,             /* b */
         0, 0, 0, 0, 0, 0, 0, 4, /* d */
         0, 0, 0, 0, 0, 0, 0, 6, /* f */
     };
-    uint8_t result[sizeof(expected)];
-    g_assert_cmpint(qemu_get_buffer(loading, result, sizeof(result)), ==,
-                    sizeof(result));
-    g_assert(!qemu_file_get_error(loading));
-    g_assert_cmpint(memcmp(result, expected, sizeof(result)), ==, 0);
-
-
-    /* Must reach EOF */
-    qemu_get_byte(loading);
-    g_assert_cmpint(qemu_file_get_error(loading), ==, -EIO);
+    check_mem_file(fsave, expected, sizeof(expected));
 
-    qemu_fclose(loading);
+    qemu_fclose(fsave);
 }
 
 static void test_load_noskip(void)
 {
-    QEMUFile *fsave = open_test_file(true);
     uint8_t buf[] = {
         0, 0, 0, 10,             /* a */
         0, 0, 0, 20,             /* b */
@@ -442,10 +449,8 @@ static void test_load_noskip(void)
         0, 0, 0, 0, 0, 0, 0, 60, /* f */
         QEMU_VM_EOF, /* just to ensure we won't get EOF reported prematurely */
     };
-    qemu_put_buffer(fsave, buf, sizeof(buf));
-    qemu_fclose(fsave);
 
-    QEMUFile *loading = open_test_file(false);
+    QEMUFile *loading = open_mem_file_read(buf, sizeof(buf));
     TestStruct obj = { .skip_c_e = false };
     vmstate_load_state(loading, &vmstate_skipping, &obj, 2);
     g_assert(!qemu_file_get_error(loading));
@@ -460,7 +465,6 @@ static void test_load_noskip(void)
 
 static void test_load_skip(void)
 {
-    QEMUFile *fsave = open_test_file(true);
     uint8_t buf[] = {
         0, 0, 0, 10,             /* a */
         0, 0, 0, 20,             /* b */
@@ -468,10 +472,8 @@ static void test_load_skip(void)
         0, 0, 0, 0, 0, 0, 0, 60, /* f */
         QEMU_VM_EOF, /* just to ensure we won't get EOF reported prematurely */
     };
-    qemu_put_buffer(fsave, buf, sizeof(buf));
-    qemu_fclose(fsave);
 
-    QEMUFile *loading = open_test_file(false);
+    QEMUFile *loading = open_mem_file_read(buf, sizeof(buf));
     TestStruct obj = { .skip_c_e = true, .c = 300, .e = 500 };
     vmstate_load_state(loading, &vmstate_skipping, &obj, 2);
     g_assert(!qemu_file_get_error(loading));
diff --git a/vmstate.c b/vmstate.c
index ef2f87b..3dde574 100644
--- a/vmstate.c
+++ b/vmstate.c
@@ -49,9 +49,16 @@ static void *vmstate_base_addr(void *opaque, VMStateField *field, bool alloc)
 
     if (field->flags & VMS_POINTER) {
         if (alloc && (field->flags & VMS_ALLOC)) {
-            int n_elems = vmstate_n_elems(opaque, field);
-            if (n_elems) {
-                gsize size = n_elems * field->size;
+            gsize size = 0;
+            if (field->flags & VMS_VBUFFER) {
+                size = vmstate_size(opaque, field);
+            } else {
+                int n_elems = vmstate_n_elems(opaque, field);
+                if (n_elems) {
+                    size = n_elems * field->size;
+                }
+            }
+            if (size) {
                 *((void **)base_addr + field->start) = g_malloc(size);
             }
         }