[01/10] hw/audio/virtio-sound: remove command and stream mutexes

Commit Message

Volker Rümelin Jan. 4, 2024, 8:34 p.m. UTC

All code in virtio-snd.c runs with the BQL held. Remove the
command queue mutex and the stream queue mutexes. The qatomic
functions are also not needed.

Signed-off-by: Volker Rümelin <[e-mail]>
---
 hw/audio/virtio-snd.c         | 294 +++++++++++++++-------------------
 include/hw/audio/virtio-snd.h |   3 -
 2 files changed, 130 insertions(+), 167 deletions(-)

Comments

Marc-André Lureau Jan. 5, 2024, 10:10 a.m. UTC | #1

Hi

On Fri, Jan 5, 2024 at 12:35 AM Volker Rümelin <[e-mail]> wrote:
>
> All code in virtio-snd.c runs with the BQL held. Remove the
> command queue mutex and the stream queue mutexes. The qatomic
> functions are also not needed.

I am not comfortable with this assertion. Someone more familiar with
virtio.c implementation should confirm

Rust would really save us from thinking about this kind of problems,
and a standalone vhost-user implementation..

>
> Signed-off-by: Volker Rümelin <[e-mail]>
> ---
>  hw/audio/virtio-snd.c         | 294 +++++++++++++++-------------------
>  include/hw/audio/virtio-snd.h |   3 -
>  2 files changed, 130 insertions(+), 167 deletions(-)
>
> diff --git a/hw/audio/virtio-snd.c b/hw/audio/virtio-snd.c
> index ea2aeaef14..8344f61c64 100644
> --- a/hw/audio/virtio-snd.c
> +++ b/hw/audio/virtio-snd.c
> @@ -19,7 +19,6 @@
>  #include "qemu/iov.h"
>  #include "qemu/log.h"
>  #include "qemu/error-report.h"
> -#include "include/qemu/lockable.h"
>  #include "sysemu/runstate.h"
>  #include "trace.h"
>  #include "qapi/error.h"
> @@ -453,7 +452,6 @@ static uint32_t virtio_snd_pcm_prepare(VirtIOSound *s, uint32_t stream_id)
>          stream->id = stream_id;
>          stream->pcm = s->pcm;
>          stream->s = s;
> -        qemu_mutex_init(&stream->queue_mutex);
>          QSIMPLEQ_INIT(&stream->queue);
>          QSIMPLEQ_INIT(&stream->invalid);
>
> @@ -580,9 +578,7 @@ static void virtio_snd_handle_pcm_start_stop(VirtIOSound *s,
>
>      stream = virtio_snd_pcm_get_stream(s, stream_id);
>      if (stream) {
> -        WITH_QEMU_LOCK_GUARD(&stream->queue_mutex) {
> -            stream->active = start;
> -        }
> +        stream->active = start;
>          if (stream->info.direction == VIRTIO_SND_D_OUTPUT) {
>              AUD_set_active_out(stream->voice.out, start);
>          } else {
> @@ -606,13 +602,11 @@ static size_t virtio_snd_pcm_get_io_msgs_count(VirtIOSoundPCMStream *stream)
>      VirtIOSoundPCMBuffer *buffer, *next;
>      size_t count = 0;
>
> -    WITH_QEMU_LOCK_GUARD(&stream->queue_mutex) {
> -        QSIMPLEQ_FOREACH_SAFE(buffer, &stream->queue, entry, next) {
> -            count += 1;
> -        }
> -        QSIMPLEQ_FOREACH_SAFE(buffer, &stream->invalid, entry, next) {
> -            count += 1;
> -        }
> +    QSIMPLEQ_FOREACH_SAFE(buffer, &stream->queue, entry, next) {
> +        count += 1;
> +    }
> +    QSIMPLEQ_FOREACH_SAFE(buffer, &stream->invalid, entry, next) {
> +        count += 1;
>      }
>      return count;
>  }
> @@ -762,23 +756,15 @@ static void virtio_snd_process_cmdq(VirtIOSound *s)
>  {
>      virtio_snd_ctrl_command *cmd;
>
> -    if (unlikely(qatomic_read(&s->processing_cmdq))) {
> -        return;
> -    }
> -
> -    WITH_QEMU_LOCK_GUARD(&s->cmdq_mutex) {
> -        qatomic_set(&s->processing_cmdq, true);
> -        while (!QTAILQ_EMPTY(&s->cmdq)) {
> -            cmd = QTAILQ_FIRST(&s->cmdq);
> +    while (!QTAILQ_EMPTY(&s->cmdq)) {
> +        cmd = QTAILQ_FIRST(&s->cmdq);
>
> -            /* process command */
> -            process_cmd(s, cmd);
> +        /* process command */
> +        process_cmd(s, cmd);
>
> -            QTAILQ_REMOVE(&s->cmdq, cmd, next);
> +        QTAILQ_REMOVE(&s->cmdq, cmd, next);
>
> -            virtio_snd_ctrl_cmd_free(cmd);
> -        }
> -        qatomic_set(&s->processing_cmdq, false);
> +        virtio_snd_ctrl_cmd_free(cmd);
>      }
>  }
>
> @@ -840,32 +826,30 @@ static inline void empty_invalid_queue(VirtIODevice *vdev, VirtQueue *vq)
>          stream = vsnd->pcm->streams[i];
>          if (stream) {
>              any = false;
> -            WITH_QEMU_LOCK_GUARD(&stream->queue_mutex) {
> -                while (!QSIMPLEQ_EMPTY(&stream->invalid)) {
> -                    buffer = QSIMPLEQ_FIRST(&stream->invalid);
> -                    if (buffer->vq != vq) {
> -                        break;
> -                    }
> -                    any = true;
> -                    resp.status = cpu_to_le32(VIRTIO_SND_S_BAD_MSG);
> -                    iov_from_buf(buffer->elem->in_sg,
> -                                 buffer->elem->in_num,
> -                                 0,
> -                                 &resp,
> -                                 sizeof(virtio_snd_pcm_status));
> -                    virtqueue_push(vq,
> -                                   buffer->elem,
> -                                   sizeof(virtio_snd_pcm_status));
> -                    QSIMPLEQ_REMOVE_HEAD(&stream->invalid, entry);
> -                    virtio_snd_pcm_buffer_free(buffer);
> -                }
> -                if (any) {
> -                    /*
> -                     * Notify vq about virtio_snd_pcm_status responses.
> -                     * Buffer responses must be notified separately later.
> -                     */
> -                    virtio_notify(vdev, vq);
> +            while (!QSIMPLEQ_EMPTY(&stream->invalid)) {
> +                buffer = QSIMPLEQ_FIRST(&stream->invalid);
> +                if (buffer->vq != vq) {
> +                    break;
>                  }
> +                any = true;
> +                resp.status = cpu_to_le32(VIRTIO_SND_S_BAD_MSG);
> +                iov_from_buf(buffer->elem->in_sg,
> +                             buffer->elem->in_num,
> +                             0,
> +                             &resp,
> +                             sizeof(virtio_snd_pcm_status));
> +                virtqueue_push(vq,
> +                               buffer->elem,
> +                               sizeof(virtio_snd_pcm_status));
> +                QSIMPLEQ_REMOVE_HEAD(&stream->invalid, entry);
> +                virtio_snd_pcm_buffer_free(buffer);
> +            }
> +            if (any) {
> +                /*
> +                 * Notify vq about virtio_snd_pcm_status responses.
> +                 * Buffer responses must be notified separately later.
> +                 */
> +                virtio_notify(vdev, vq);
>              }
>          }
>      }
> @@ -924,28 +908,24 @@ static void virtio_snd_handle_tx_xfer(VirtIODevice *vdev, VirtQueue *vq)
>              goto tx_err;
>          }
>
> -        WITH_QEMU_LOCK_GUARD(&stream->queue_mutex) {
> -            size = iov_size(elem->out_sg, elem->out_num) - msg_sz;
> +        size = iov_size(elem->out_sg, elem->out_num) - msg_sz;
>
> -            buffer = g_malloc0(sizeof(VirtIOSoundPCMBuffer) + size);
> -            buffer->elem = elem;
> -            buffer->populated = false;
> -            buffer->vq = vq;
> -            buffer->size = size;
> -            buffer->offset = 0;
> +        buffer = g_malloc0(sizeof(VirtIOSoundPCMBuffer) + size);
> +        buffer->elem = elem;
> +        buffer->populated = false;
> +        buffer->vq = vq;
> +        buffer->size = size;
> +        buffer->offset = 0;
>
> -            QSIMPLEQ_INSERT_TAIL(&stream->queue, buffer, entry);
> -        }
> +        QSIMPLEQ_INSERT_TAIL(&stream->queue, buffer, entry);
>          continue;
>
>  tx_err:
> -        WITH_QEMU_LOCK_GUARD(&stream->queue_mutex) {
> -            must_empty_invalid_queue = true;
> -            buffer = g_malloc0(sizeof(VirtIOSoundPCMBuffer));
> -            buffer->elem = elem;
> -            buffer->vq = vq;
> -            QSIMPLEQ_INSERT_TAIL(&stream->invalid, buffer, entry);
> -        }
> +        must_empty_invalid_queue = true;
> +        buffer = g_malloc0(sizeof(VirtIOSoundPCMBuffer));
> +        buffer->elem = elem;
> +        buffer->vq = vq;
> +        QSIMPLEQ_INSERT_TAIL(&stream->invalid, buffer, entry);
>      }
>
>      if (must_empty_invalid_queue) {
> @@ -1005,26 +985,23 @@ static void virtio_snd_handle_rx_xfer(VirtIODevice *vdev, VirtQueue *vq)
>          if (stream == NULL || stream->info.direction != VIRTIO_SND_D_INPUT) {
>              goto rx_err;
>          }
> -        WITH_QEMU_LOCK_GUARD(&stream->queue_mutex) {
> -            size = iov_size(elem->in_sg, elem->in_num) -
> -                sizeof(virtio_snd_pcm_status);
> -            buffer = g_malloc0(sizeof(VirtIOSoundPCMBuffer) + size);
> -            buffer->elem = elem;
> -            buffer->vq = vq;
> -            buffer->size = 0;
> -            buffer->offset = 0;
> -            QSIMPLEQ_INSERT_TAIL(&stream->queue, buffer, entry);
> -        }
> +        size = iov_size(elem->in_sg, elem->in_num) -
> +            sizeof(virtio_snd_pcm_status);
> +        buffer = g_malloc0(sizeof(VirtIOSoundPCMBuffer) + size);
> +        buffer->elem = elem;
> +        buffer->vq = vq;
> +        buffer->size = 0;
> +        buffer->offset = 0;
> +        QSIMPLEQ_INSERT_TAIL(&stream->queue, buffer, entry);
>          continue;
>
>  rx_err:
> -        WITH_QEMU_LOCK_GUARD(&stream->queue_mutex) {
> -            must_empty_invalid_queue = true;
> -            buffer = g_malloc0(sizeof(VirtIOSoundPCMBuffer));
> -            buffer->elem = elem;
> -            buffer->vq = vq;
> -            QSIMPLEQ_INSERT_TAIL(&stream->invalid, buffer, entry);
> -        }
> +        must_empty_invalid_queue = true;
> +        buffer = g_malloc0(sizeof(VirtIOSoundPCMBuffer));
> +        buffer->elem = elem;
> +        buffer->vq = vq;
> +        QSIMPLEQ_INSERT_TAIL(&stream->invalid, buffer, entry);
> +
>      }
>
>      if (must_empty_invalid_queue) {
> @@ -1122,7 +1099,6 @@ static void virtio_snd_realize(DeviceState *dev, Error **errp)
>          virtio_add_queue(vdev, 64, virtio_snd_handle_tx_xfer);
>      vsnd->queues[VIRTIO_SND_VQ_RX] =
>          virtio_add_queue(vdev, 64, virtio_snd_handle_rx_xfer);
> -    qemu_mutex_init(&vsnd->cmdq_mutex);
>      QTAILQ_INIT(&vsnd->cmdq);
>
>      for (uint32_t i = 0; i < vsnd->snd_conf.streams; i++) {
> @@ -1182,50 +1158,48 @@ static void virtio_snd_pcm_out_cb(void *data, int available)
>      VirtIOSoundPCMBuffer *buffer;
>      size_t size;
>
> -    WITH_QEMU_LOCK_GUARD(&stream->queue_mutex) {
> -        while (!QSIMPLEQ_EMPTY(&stream->queue)) {
> -            buffer = QSIMPLEQ_FIRST(&stream->queue);
> -            if (!virtio_queue_ready(buffer->vq)) {
> -                return;
> +    while (!QSIMPLEQ_EMPTY(&stream->queue)) {
> +        buffer = QSIMPLEQ_FIRST(&stream->queue);
> +        if (!virtio_queue_ready(buffer->vq)) {
> +            return;
> +        }
> +        if (!stream->active) {
> +            /* Stream has stopped, so do not perform AUD_write. */
> +            return_tx_buffer(stream, buffer);
> +            continue;
> +        }
> +        if (!buffer->populated) {
> +            iov_to_buf(buffer->elem->out_sg,
> +                       buffer->elem->out_num,
> +                       sizeof(virtio_snd_pcm_xfer),
> +                       buffer->data,
> +                       buffer->size);
> +            buffer->populated = true;
> +        }
> +        for (;;) {
> +            size = AUD_write(stream->voice.out,
> +                             buffer->data + buffer->offset,
> +                             MIN(buffer->size, available));
> +            assert(size <= MIN(buffer->size, available));
> +            if (size == 0) {
> +                /* break out of both loops */
> +                available = 0;
> +                break;
>              }
> -            if (!stream->active) {
> -                /* Stream has stopped, so do not perform AUD_write. */
> +            buffer->size -= size;
> +            buffer->offset += size;
> +            available -= size;
> +            if (buffer->size < 1) {
>                  return_tx_buffer(stream, buffer);
> -                continue;
> -            }
> -            if (!buffer->populated) {
> -                iov_to_buf(buffer->elem->out_sg,
> -                           buffer->elem->out_num,
> -                           sizeof(virtio_snd_pcm_xfer),
> -                           buffer->data,
> -                           buffer->size);
> -                buffer->populated = true;
> -            }
> -            for (;;) {
> -                size = AUD_write(stream->voice.out,
> -                                 buffer->data + buffer->offset,
> -                                 MIN(buffer->size, available));
> -                assert(size <= MIN(buffer->size, available));
> -                if (size == 0) {
> -                    /* break out of both loops */
> -                    available = 0;
> -                    break;
> -                }
> -                buffer->size -= size;
> -                buffer->offset += size;
> -                available -= size;
> -                if (buffer->size < 1) {
> -                    return_tx_buffer(stream, buffer);
> -                    break;
> -                }
> -                if (!available) {
> -                    break;
> -                }
> +                break;
>              }
>              if (!available) {
>                  break;
>              }
>          }
> +        if (!available) {
> +            break;
> +        }
>      }
>  }
>
> @@ -1276,41 +1250,39 @@ static void virtio_snd_pcm_in_cb(void *data, int available)
>      VirtIOSoundPCMBuffer *buffer;
>      size_t size;
>
> -    WITH_QEMU_LOCK_GUARD(&stream->queue_mutex) {
> -        while (!QSIMPLEQ_EMPTY(&stream->queue)) {
> -            buffer = QSIMPLEQ_FIRST(&stream->queue);
> -            if (!virtio_queue_ready(buffer->vq)) {
> -                return;
> +    while (!QSIMPLEQ_EMPTY(&stream->queue)) {
> +        buffer = QSIMPLEQ_FIRST(&stream->queue);
> +        if (!virtio_queue_ready(buffer->vq)) {
> +            return;
> +        }
> +        if (!stream->active) {
> +            /* Stream has stopped, so do not perform AUD_read. */
> +            return_rx_buffer(stream, buffer);
> +            continue;
> +        }
> +
> +        for (;;) {
> +            size = AUD_read(stream->voice.in,
> +                            buffer->data + buffer->size,
> +                            MIN(available, (stream->params.period_bytes -
> +                                            buffer->size)));
> +            if (!size) {
> +                available = 0;
> +                break;
>              }
> -            if (!stream->active) {
> -                /* Stream has stopped, so do not perform AUD_read. */
> +            buffer->size += size;
> +            available -= size;
> +            if (buffer->size >= stream->params.period_bytes) {
>                  return_rx_buffer(stream, buffer);
> -                continue;
> -            }
> -
> -            for (;;) {
> -                size = AUD_read(stream->voice.in,
> -                        buffer->data + buffer->size,
> -                        MIN(available, (stream->params.period_bytes -
> -                                        buffer->size)));
> -                if (!size) {
> -                    available = 0;
> -                    break;
> -                }
> -                buffer->size += size;
> -                available -= size;
> -                if (buffer->size >= stream->params.period_bytes) {
> -                    return_rx_buffer(stream, buffer);
> -                    break;
> -                }
> -                if (!available) {
> -                    break;
> -                }
> +                break;
>              }
>              if (!available) {
>                  break;
>              }
>          }
> +        if (!available) {
> +            break;
> +        }
>      }
>  }
>
> @@ -1327,11 +1299,9 @@ static inline void virtio_snd_pcm_flush(VirtIOSoundPCMStream *stream)
>          (stream->info.direction == VIRTIO_SND_D_OUTPUT) ? return_tx_buffer :
>          return_rx_buffer;
>
> -    WITH_QEMU_LOCK_GUARD(&stream->queue_mutex) {
> -        while (!QSIMPLEQ_EMPTY(&stream->queue)) {
> -            buffer = QSIMPLEQ_FIRST(&stream->queue);
> -            cb(stream, buffer);
> -        }
> +    while (!QSIMPLEQ_EMPTY(&stream->queue)) {
> +        buffer = QSIMPLEQ_FIRST(&stream->queue);
> +        cb(stream, buffer);
>      }
>  }
>
> @@ -1351,7 +1321,6 @@ static void virtio_snd_unrealize(DeviceState *dev)
>                  if (stream) {
>                      virtio_snd_process_cmdq(stream->s);
>                      virtio_snd_pcm_close(stream);
> -                    qemu_mutex_destroy(&stream->queue_mutex);
>                      g_free(stream);
>                  }
>              }
> @@ -1362,7 +1331,6 @@ static void virtio_snd_unrealize(DeviceState *dev)
>          vsnd->pcm = NULL;
>      }
>      AUD_remove_card(&vsnd->card);
> -    qemu_mutex_destroy(&vsnd->cmdq_mutex);
>      virtio_delete_queue(vsnd->queues[VIRTIO_SND_VQ_CONTROL]);
>      virtio_delete_queue(vsnd->queues[VIRTIO_SND_VQ_EVENT]);
>      virtio_delete_queue(vsnd->queues[VIRTIO_SND_VQ_TX]);
> @@ -1376,12 +1344,10 @@ static void virtio_snd_reset(VirtIODevice *vdev)
>      VirtIOSound *s = VIRTIO_SND(vdev);
>      virtio_snd_ctrl_command *cmd;
>
> -    WITH_QEMU_LOCK_GUARD(&s->cmdq_mutex) {
> -        while (!QTAILQ_EMPTY(&s->cmdq)) {
> -            cmd = QTAILQ_FIRST(&s->cmdq);
> -            QTAILQ_REMOVE(&s->cmdq, cmd, next);
> -            virtio_snd_ctrl_cmd_free(cmd);
> -        }
> +    while (!QTAILQ_EMPTY(&s->cmdq)) {
> +        cmd = QTAILQ_FIRST(&s->cmdq);
> +        QTAILQ_REMOVE(&s->cmdq, cmd, next);
> +        virtio_snd_ctrl_cmd_free(cmd);
>      }
>  }
>
> diff --git a/include/hw/audio/virtio-snd.h b/include/hw/audio/virtio-snd.h
> index c3767f442b..ea6315f59b 100644
> --- a/include/hw/audio/virtio-snd.h
> +++ b/include/hw/audio/virtio-snd.h
> @@ -148,7 +148,6 @@ struct VirtIOSoundPCMStream {
>          SWVoiceIn *in;
>          SWVoiceOut *out;
>      } voice;
> -    QemuMutex queue_mutex;
>      bool active;
>      QSIMPLEQ_HEAD(, VirtIOSoundPCMBuffer) queue;
>      QSIMPLEQ_HEAD(, VirtIOSoundPCMBuffer) invalid;
> @@ -220,9 +219,7 @@ struct VirtIOSound {
>      QEMUSoundCard card;
>      VMChangeStateEntry *vmstate;
>      virtio_snd_config snd_conf;
> -    QemuMutex cmdq_mutex;
>      QTAILQ_HEAD(, virtio_snd_ctrl_command) cmdq;
> -    bool processing_cmdq;
>  };
>
>  struct virtio_snd_ctrl_command {
> --
> 2.35.3
>
>

Patch

diff --git a/hw/audio/virtio-snd.c b/hw/audio/virtio-snd.c
index ea2aeaef14..8344f61c64 100644
--- a/hw/audio/virtio-snd.c
+++ b/hw/audio/virtio-snd.c
@@ -19,7 +19,6 @@ 
 #include "qemu/iov.h"
 #include "qemu/log.h"
 #include "qemu/error-report.h"
-#include "include/qemu/lockable.h"
 #include "sysemu/runstate.h"
 #include "trace.h"
 #include "qapi/error.h"
@@ -453,7 +452,6 @@  static uint32_t virtio_snd_pcm_prepare(VirtIOSound *s, uint32_t stream_id)
         stream->id = stream_id;
         stream->pcm = s->pcm;
         stream->s = s;
-        qemu_mutex_init(&stream->queue_mutex);
         QSIMPLEQ_INIT(&stream->queue);
         QSIMPLEQ_INIT(&stream->invalid);
 
@@ -580,9 +578,7 @@  static void virtio_snd_handle_pcm_start_stop(VirtIOSound *s,
 
     stream = virtio_snd_pcm_get_stream(s, stream_id);
     if (stream) {
-        WITH_QEMU_LOCK_GUARD(&stream->queue_mutex) {
-            stream->active = start;
-        }
+        stream->active = start;
         if (stream->info.direction == VIRTIO_SND_D_OUTPUT) {
             AUD_set_active_out(stream->voice.out, start);
         } else {
@@ -606,13 +602,11 @@  static size_t virtio_snd_pcm_get_io_msgs_count(VirtIOSoundPCMStream *stream)
     VirtIOSoundPCMBuffer *buffer, *next;
     size_t count = 0;
 
-    WITH_QEMU_LOCK_GUARD(&stream->queue_mutex) {
-        QSIMPLEQ_FOREACH_SAFE(buffer, &stream->queue, entry, next) {
-            count += 1;
-        }
-        QSIMPLEQ_FOREACH_SAFE(buffer, &stream->invalid, entry, next) {
-            count += 1;
-        }
+    QSIMPLEQ_FOREACH_SAFE(buffer, &stream->queue, entry, next) {
+        count += 1;
+    }
+    QSIMPLEQ_FOREACH_SAFE(buffer, &stream->invalid, entry, next) {
+        count += 1;
     }
     return count;
 }
@@ -762,23 +756,15 @@  static void virtio_snd_process_cmdq(VirtIOSound *s)
 {
     virtio_snd_ctrl_command *cmd;
 
-    if (unlikely(qatomic_read(&s->processing_cmdq))) {
-        return;
-    }
-
-    WITH_QEMU_LOCK_GUARD(&s->cmdq_mutex) {
-        qatomic_set(&s->processing_cmdq, true);
-        while (!QTAILQ_EMPTY(&s->cmdq)) {
-            cmd = QTAILQ_FIRST(&s->cmdq);
+    while (!QTAILQ_EMPTY(&s->cmdq)) {
+        cmd = QTAILQ_FIRST(&s->cmdq);
 
-            /* process command */
-            process_cmd(s, cmd);
+        /* process command */
+        process_cmd(s, cmd);
 
-            QTAILQ_REMOVE(&s->cmdq, cmd, next);
+        QTAILQ_REMOVE(&s->cmdq, cmd, next);
 
-            virtio_snd_ctrl_cmd_free(cmd);
-        }
-        qatomic_set(&s->processing_cmdq, false);
+        virtio_snd_ctrl_cmd_free(cmd);
     }
 }
 
@@ -840,32 +826,30 @@  static inline void empty_invalid_queue(VirtIODevice *vdev, VirtQueue *vq)
         stream = vsnd->pcm->streams[i];
         if (stream) {
             any = false;
-            WITH_QEMU_LOCK_GUARD(&stream->queue_mutex) {
-                while (!QSIMPLEQ_EMPTY(&stream->invalid)) {
-                    buffer = QSIMPLEQ_FIRST(&stream->invalid);
-                    if (buffer->vq != vq) {
-                        break;
-                    }
-                    any = true;
-                    resp.status = cpu_to_le32(VIRTIO_SND_S_BAD_MSG);
-                    iov_from_buf(buffer->elem->in_sg,
-                                 buffer->elem->in_num,
-                                 0,
-                                 &resp,
-                                 sizeof(virtio_snd_pcm_status));
-                    virtqueue_push(vq,
-                                   buffer->elem,
-                                   sizeof(virtio_snd_pcm_status));
-                    QSIMPLEQ_REMOVE_HEAD(&stream->invalid, entry);
-                    virtio_snd_pcm_buffer_free(buffer);
-                }
-                if (any) {
-                    /*
-                     * Notify vq about virtio_snd_pcm_status responses.
-                     * Buffer responses must be notified separately later.
-                     */
-                    virtio_notify(vdev, vq);
+            while (!QSIMPLEQ_EMPTY(&stream->invalid)) {
+                buffer = QSIMPLEQ_FIRST(&stream->invalid);
+                if (buffer->vq != vq) {
+                    break;
                 }
+                any = true;
+                resp.status = cpu_to_le32(VIRTIO_SND_S_BAD_MSG);
+                iov_from_buf(buffer->elem->in_sg,
+                             buffer->elem->in_num,
+                             0,
+                             &resp,
+                             sizeof(virtio_snd_pcm_status));
+                virtqueue_push(vq,
+                               buffer->elem,
+                               sizeof(virtio_snd_pcm_status));
+                QSIMPLEQ_REMOVE_HEAD(&stream->invalid, entry);
+                virtio_snd_pcm_buffer_free(buffer);
+            }
+            if (any) {
+                /*
+                 * Notify vq about virtio_snd_pcm_status responses.
+                 * Buffer responses must be notified separately later.
+                 */
+                virtio_notify(vdev, vq);
             }
         }
     }
@@ -924,28 +908,24 @@  static void virtio_snd_handle_tx_xfer(VirtIODevice *vdev, VirtQueue *vq)
             goto tx_err;
         }
 
-        WITH_QEMU_LOCK_GUARD(&stream->queue_mutex) {
-            size = iov_size(elem->out_sg, elem->out_num) - msg_sz;
+        size = iov_size(elem->out_sg, elem->out_num) - msg_sz;
 
-            buffer = g_malloc0(sizeof(VirtIOSoundPCMBuffer) + size);
-            buffer->elem = elem;
-            buffer->populated = false;
-            buffer->vq = vq;
-            buffer->size = size;
-            buffer->offset = 0;
+        buffer = g_malloc0(sizeof(VirtIOSoundPCMBuffer) + size);
+        buffer->elem = elem;
+        buffer->populated = false;
+        buffer->vq = vq;
+        buffer->size = size;
+        buffer->offset = 0;
 
-            QSIMPLEQ_INSERT_TAIL(&stream->queue, buffer, entry);
-        }
+        QSIMPLEQ_INSERT_TAIL(&stream->queue, buffer, entry);
         continue;
 
 tx_err:
-        WITH_QEMU_LOCK_GUARD(&stream->queue_mutex) {
-            must_empty_invalid_queue = true;
-            buffer = g_malloc0(sizeof(VirtIOSoundPCMBuffer));
-            buffer->elem = elem;
-            buffer->vq = vq;
-            QSIMPLEQ_INSERT_TAIL(&stream->invalid, buffer, entry);
-        }
+        must_empty_invalid_queue = true;
+        buffer = g_malloc0(sizeof(VirtIOSoundPCMBuffer));
+        buffer->elem = elem;
+        buffer->vq = vq;
+        QSIMPLEQ_INSERT_TAIL(&stream->invalid, buffer, entry);
     }
 
     if (must_empty_invalid_queue) {
@@ -1005,26 +985,23 @@  static void virtio_snd_handle_rx_xfer(VirtIODevice *vdev, VirtQueue *vq)
         if (stream == NULL || stream->info.direction != VIRTIO_SND_D_INPUT) {
             goto rx_err;
         }
-        WITH_QEMU_LOCK_GUARD(&stream->queue_mutex) {
-            size = iov_size(elem->in_sg, elem->in_num) -
-                sizeof(virtio_snd_pcm_status);
-            buffer = g_malloc0(sizeof(VirtIOSoundPCMBuffer) + size);
-            buffer->elem = elem;
-            buffer->vq = vq;
-            buffer->size = 0;
-            buffer->offset = 0;
-            QSIMPLEQ_INSERT_TAIL(&stream->queue, buffer, entry);
-        }
+        size = iov_size(elem->in_sg, elem->in_num) -
+            sizeof(virtio_snd_pcm_status);
+        buffer = g_malloc0(sizeof(VirtIOSoundPCMBuffer) + size);
+        buffer->elem = elem;
+        buffer->vq = vq;
+        buffer->size = 0;
+        buffer->offset = 0;
+        QSIMPLEQ_INSERT_TAIL(&stream->queue, buffer, entry);
         continue;
 
 rx_err:
-        WITH_QEMU_LOCK_GUARD(&stream->queue_mutex) {
-            must_empty_invalid_queue = true;
-            buffer = g_malloc0(sizeof(VirtIOSoundPCMBuffer));
-            buffer->elem = elem;
-            buffer->vq = vq;
-            QSIMPLEQ_INSERT_TAIL(&stream->invalid, buffer, entry);
-        }
+        must_empty_invalid_queue = true;
+        buffer = g_malloc0(sizeof(VirtIOSoundPCMBuffer));
+        buffer->elem = elem;
+        buffer->vq = vq;
+        QSIMPLEQ_INSERT_TAIL(&stream->invalid, buffer, entry);
+
     }
 
     if (must_empty_invalid_queue) {
@@ -1122,7 +1099,6 @@  static void virtio_snd_realize(DeviceState *dev, Error **errp)
         virtio_add_queue(vdev, 64, virtio_snd_handle_tx_xfer);
     vsnd->queues[VIRTIO_SND_VQ_RX] =
         virtio_add_queue(vdev, 64, virtio_snd_handle_rx_xfer);
-    qemu_mutex_init(&vsnd->cmdq_mutex);
     QTAILQ_INIT(&vsnd->cmdq);
 
     for (uint32_t i = 0; i < vsnd->snd_conf.streams; i++) {
@@ -1182,50 +1158,48 @@  static void virtio_snd_pcm_out_cb(void *data, int available)
     VirtIOSoundPCMBuffer *buffer;
     size_t size;
 
-    WITH_QEMU_LOCK_GUARD(&stream->queue_mutex) {
-        while (!QSIMPLEQ_EMPTY(&stream->queue)) {
-            buffer = QSIMPLEQ_FIRST(&stream->queue);
-            if (!virtio_queue_ready(buffer->vq)) {
-                return;
+    while (!QSIMPLEQ_EMPTY(&stream->queue)) {
+        buffer = QSIMPLEQ_FIRST(&stream->queue);
+        if (!virtio_queue_ready(buffer->vq)) {
+            return;
+        }
+        if (!stream->active) {
+            /* Stream has stopped, so do not perform AUD_write. */
+            return_tx_buffer(stream, buffer);
+            continue;
+        }
+        if (!buffer->populated) {
+            iov_to_buf(buffer->elem->out_sg,
+                       buffer->elem->out_num,
+                       sizeof(virtio_snd_pcm_xfer),
+                       buffer->data,
+                       buffer->size);
+            buffer->populated = true;
+        }
+        for (;;) {
+            size = AUD_write(stream->voice.out,
+                             buffer->data + buffer->offset,
+                             MIN(buffer->size, available));
+            assert(size <= MIN(buffer->size, available));
+            if (size == 0) {
+                /* break out of both loops */
+                available = 0;
+                break;
             }
-            if (!stream->active) {
-                /* Stream has stopped, so do not perform AUD_write. */
+            buffer->size -= size;
+            buffer->offset += size;
+            available -= size;
+            if (buffer->size < 1) {
                 return_tx_buffer(stream, buffer);
-                continue;
-            }
-            if (!buffer->populated) {
-                iov_to_buf(buffer->elem->out_sg,
-                           buffer->elem->out_num,
-                           sizeof(virtio_snd_pcm_xfer),
-                           buffer->data,
-                           buffer->size);
-                buffer->populated = true;
-            }
-            for (;;) {
-                size = AUD_write(stream->voice.out,
-                                 buffer->data + buffer->offset,
-                                 MIN(buffer->size, available));
-                assert(size <= MIN(buffer->size, available));
-                if (size == 0) {
-                    /* break out of both loops */
-                    available = 0;
-                    break;
-                }
-                buffer->size -= size;
-                buffer->offset += size;
-                available -= size;
-                if (buffer->size < 1) {
-                    return_tx_buffer(stream, buffer);
-                    break;
-                }
-                if (!available) {
-                    break;
-                }
+                break;
             }
             if (!available) {
                 break;
             }
         }
+        if (!available) {
+            break;
+        }
     }
 }
 
@@ -1276,41 +1250,39 @@  static void virtio_snd_pcm_in_cb(void *data, int available)
     VirtIOSoundPCMBuffer *buffer;
     size_t size;
 
-    WITH_QEMU_LOCK_GUARD(&stream->queue_mutex) {
-        while (!QSIMPLEQ_EMPTY(&stream->queue)) {
-            buffer = QSIMPLEQ_FIRST(&stream->queue);
-            if (!virtio_queue_ready(buffer->vq)) {
-                return;
+    while (!QSIMPLEQ_EMPTY(&stream->queue)) {
+        buffer = QSIMPLEQ_FIRST(&stream->queue);
+        if (!virtio_queue_ready(buffer->vq)) {
+            return;
+        }
+        if (!stream->active) {
+            /* Stream has stopped, so do not perform AUD_read. */
+            return_rx_buffer(stream, buffer);
+            continue;
+        }
+
+        for (;;) {
+            size = AUD_read(stream->voice.in,
+                            buffer->data + buffer->size,
+                            MIN(available, (stream->params.period_bytes -
+                                            buffer->size)));
+            if (!size) {
+                available = 0;
+                break;
             }
-            if (!stream->active) {
-                /* Stream has stopped, so do not perform AUD_read. */
+            buffer->size += size;
+            available -= size;
+            if (buffer->size >= stream->params.period_bytes) {
                 return_rx_buffer(stream, buffer);
-                continue;
-            }
-
-            for (;;) {
-                size = AUD_read(stream->voice.in,
-                        buffer->data + buffer->size,
-                        MIN(available, (stream->params.period_bytes -
-                                        buffer->size)));
-                if (!size) {
-                    available = 0;
-                    break;
-                }
-                buffer->size += size;
-                available -= size;
-                if (buffer->size >= stream->params.period_bytes) {
-                    return_rx_buffer(stream, buffer);
-                    break;
-                }
-                if (!available) {
-                    break;
-                }
+                break;
             }
             if (!available) {
                 break;
             }
         }
+        if (!available) {
+            break;
+        }
     }
 }
 
@@ -1327,11 +1299,9 @@  static inline void virtio_snd_pcm_flush(VirtIOSoundPCMStream *stream)
         (stream->info.direction == VIRTIO_SND_D_OUTPUT) ? return_tx_buffer :
         return_rx_buffer;
 
-    WITH_QEMU_LOCK_GUARD(&stream->queue_mutex) {
-        while (!QSIMPLEQ_EMPTY(&stream->queue)) {
-            buffer = QSIMPLEQ_FIRST(&stream->queue);
-            cb(stream, buffer);
-        }
+    while (!QSIMPLEQ_EMPTY(&stream->queue)) {
+        buffer = QSIMPLEQ_FIRST(&stream->queue);
+        cb(stream, buffer);
     }
 }
 
@@ -1351,7 +1321,6 @@  static void virtio_snd_unrealize(DeviceState *dev)
                 if (stream) {
                     virtio_snd_process_cmdq(stream->s);
                     virtio_snd_pcm_close(stream);
-                    qemu_mutex_destroy(&stream->queue_mutex);
                     g_free(stream);
                 }
             }
@@ -1362,7 +1331,6 @@  static void virtio_snd_unrealize(DeviceState *dev)
         vsnd->pcm = NULL;
     }
     AUD_remove_card(&vsnd->card);
-    qemu_mutex_destroy(&vsnd->cmdq_mutex);
     virtio_delete_queue(vsnd->queues[VIRTIO_SND_VQ_CONTROL]);
     virtio_delete_queue(vsnd->queues[VIRTIO_SND_VQ_EVENT]);
     virtio_delete_queue(vsnd->queues[VIRTIO_SND_VQ_TX]);
@@ -1376,12 +1344,10 @@  static void virtio_snd_reset(VirtIODevice *vdev)
     VirtIOSound *s = VIRTIO_SND(vdev);
     virtio_snd_ctrl_command *cmd;
 
-    WITH_QEMU_LOCK_GUARD(&s->cmdq_mutex) {
-        while (!QTAILQ_EMPTY(&s->cmdq)) {
-            cmd = QTAILQ_FIRST(&s->cmdq);
-            QTAILQ_REMOVE(&s->cmdq, cmd, next);
-            virtio_snd_ctrl_cmd_free(cmd);
-        }
+    while (!QTAILQ_EMPTY(&s->cmdq)) {
+        cmd = QTAILQ_FIRST(&s->cmdq);
+        QTAILQ_REMOVE(&s->cmdq, cmd, next);
+        virtio_snd_ctrl_cmd_free(cmd);
     }
 }
 
diff --git a/include/hw/audio/virtio-snd.h b/include/hw/audio/virtio-snd.h
index c3767f442b..ea6315f59b 100644
--- a/include/hw/audio/virtio-snd.h
+++ b/include/hw/audio/virtio-snd.h
@@ -148,7 +148,6 @@  struct VirtIOSoundPCMStream {
         SWVoiceIn *in;
         SWVoiceOut *out;
     } voice;
-    QemuMutex queue_mutex;
     bool active;
     QSIMPLEQ_HEAD(, VirtIOSoundPCMBuffer) queue;
     QSIMPLEQ_HEAD(, VirtIOSoundPCMBuffer) invalid;
@@ -220,9 +219,7 @@  struct VirtIOSound {
     QEMUSoundCard card;
     VMChangeStateEntry *vmstate;
     virtio_snd_config snd_conf;
-    QemuMutex cmdq_mutex;
     QTAILQ_HEAD(, virtio_snd_ctrl_command) cmdq;
-    bool processing_cmdq;
 };
 
 struct virtio_snd_ctrl_command {