Re: [PATCH v3 9/9] hw/audio/virtio-sound: add missing vmstate fields

[Manos Pitsidianakis <manos.pitsidianakis@linaro.org>]

On Fri, 26 Jun 2026 15:35, Alexander Mikhalitsyn <alexander@mihalicyn.com> wrote:
>From: Volker Rümelin <vr_qemu@t-online.de>
>
>The virtio-sound device is currently not migratable. Add the
>missing VMSTATE fields, enable migration and reconnect the audio
>streams after migration.
>
>The queue_inuse[] array variables mimic the inuse variable in
>struct VirtQueue which is private. They are needed to restart
>the virtio queues after migration.
>
>Signed-off-by: Volker Rümelin <vr_qemu@t-online.de>
>[AM: trivial rebase changes]
>Signed-off-by: Alexander Mikhalitsyn <aleksandr.mikhalitsyn@futurfusion.io>
>---
>v3:
>	- added latency_bytes field to VMStateDescription
>
>	As suggested by Marc-André Lureau:
>	- removed the "rc" variable from virtio_snd_post_load()
>	- dropped info field from VMStateDescription, because
>	  it can't be modified by guest and initialized only from realize
>	- added minimum_version_id/version_id so we can extend VMStateDescription
>	  without breaking compatibility in the future
>---
> hw/audio/virtio-snd.c         | 80 +++++++++++++++++++++++++++++++----
> include/hw/audio/virtio-snd.h |  1 +
> 2 files changed, 73 insertions(+), 8 deletions(-)
>
>diff --git a/hw/audio/virtio-snd.c b/hw/audio/virtio-snd.c
>index 81ba1e1a277..7af0b63c03b 100644
>--- a/hw/audio/virtio-snd.c
>+++ b/hw/audio/virtio-snd.c
>@@ -24,7 +24,6 @@
> #include "qapi/error.h"
> #include "hw/audio/virtio-snd.h"
> 
>-#define VIRTIO_SOUND_VM_VERSION 1
> #define VIRTIO_SOUND_JACK_DEFAULT 0
> #define VIRTIO_SOUND_STREAM_DEFAULT 2
> #define VIRTIO_SOUND_CHMAP_DEFAULT 0
>@@ -78,17 +77,40 @@ static uint32_t supported_rates = BIT(VIRTIO_SND_PCM_RATE_5512)
>                                 | BIT(VIRTIO_SND_PCM_RATE_192000)
>                                 | BIT(VIRTIO_SND_PCM_RATE_384000);
> 
>+static const VMStateDescription vmstate_virtio_snd_stream = {
>+    .name = "virtio-sound-stream",
>+    .version_id = 1,
>+    .minimum_version_id = 1,
>+    .fields = (const VMStateField[]) {
>+        VMSTATE_UINT32(state, VirtIOSoundPCMStream),
>+        VMSTATE_UINT32(params.buffer_bytes, VirtIOSoundPCMStream),
>+        VMSTATE_UINT32(params.period_bytes, VirtIOSoundPCMStream),
>+        VMSTATE_UINT32(params.features, VirtIOSoundPCMStream),
>+        VMSTATE_UINT8(params.channels, VirtIOSoundPCMStream),
>+        VMSTATE_UINT8(params.format, VirtIOSoundPCMStream),
>+        VMSTATE_UINT8(params.rate, VirtIOSoundPCMStream),
>+        VMSTATE_UINT32(latency_bytes, VirtIOSoundPCMStream),
>+        VMSTATE_END_OF_LIST()
>+    },
>+};
>+
> static const VMStateDescription vmstate_virtio_snd_device = {
>-    .name = TYPE_VIRTIO_SND,
>-    .version_id = VIRTIO_SOUND_VM_VERSION,
>-    .minimum_version_id = VIRTIO_SOUND_VM_VERSION,
>+    .name = "virtio-sound-device",
>+    .version_id = 1,
>+    .minimum_version_id = 1,
>+    .fields = (const VMStateField[]) {
>+        VMSTATE_UINT32_ARRAY(queue_inuse, VirtIOSound, VIRTIO_SND_VQ_MAX),
>+        VMSTATE_STRUCT_VARRAY_POINTER_UINT32(streams, VirtIOSound,
>+            snd_conf.streams,
>+            vmstate_virtio_snd_stream, VirtIOSoundPCMStream),
>+        VMSTATE_END_OF_LIST()
>+    },
> };
> 
> static const VMStateDescription vmstate_virtio_snd = {
>-    .name = TYPE_VIRTIO_SND,
>-    .unmigratable = 1,
>-    .minimum_version_id = VIRTIO_SOUND_VM_VERSION,
>-    .version_id = VIRTIO_SOUND_VM_VERSION,
>+    .name = "virtio-sound",

Why change the name? It differentiates between the device impl and 
virtio-sound-pci wrapper device.

>+    .version_id = 1,
>+    .minimum_version_id = 1,
>     .fields = (const VMStateField[]) {
>         VMSTATE_VIRTIO_DEVICE,
>         VMSTATE_END_OF_LIST()
>@@ -799,6 +821,7 @@ process_cmd(VirtIOSound *s, virtio_snd_ctrl_command *cmd)
>                  sizeof(virtio_snd_hdr));
>     virtqueue_push(cmd->vq, cmd->elem,
>                    sizeof(virtio_snd_hdr) + cmd->payload_size);
>+    s->queue_inuse[VIRTIO_SND_VQ_CONTROL] -= 1;

Let's do a g_assert that this is > 0 before decrementing it.

>     virtio_notify(VIRTIO_DEVICE(s), cmd->vq);
> }
> 
>@@ -845,6 +868,7 @@ static void virtio_snd_handle_ctrl(VirtIODevice *vdev, VirtQueue *vq)
> 
>     elem = virtqueue_pop(vq, sizeof(VirtQueueElement));
>     while (elem) {
>+        s->queue_inuse[VIRTIO_SND_VQ_CONTROL] += 1;
>         cmd = g_new0(virtio_snd_ctrl_command, 1);
>         cmd->elem = elem;
>         cmd->vq = vq;
>@@ -955,6 +979,7 @@ static void virtio_snd_handle_tx_xfer(VirtIODevice *vdev, VirtQueue *vq)
>             goto tx_err;
>         }
> 
>+        vsnd->queue_inuse[VIRTIO_SND_VQ_TX] += 1;
>         size = iov_size(elem->out_sg, elem->out_num) - msg_sz;
> 
>         buffer = g_malloc0(sizeof(VirtIOSoundPCMBuffer) + size);
>@@ -1034,6 +1059,7 @@ static void virtio_snd_handle_rx_xfer(VirtIODevice *vdev, VirtQueue *vq)
>             goto rx_err;
>         }
> 
>+        vsnd->queue_inuse[VIRTIO_SND_VQ_RX] += 1;
>         size = iov_size(elem->in_sg, elem->in_num) -
>             sizeof(virtio_snd_pcm_status);
>         buffer = g_malloc0(sizeof(VirtIOSoundPCMBuffer) + size);
>@@ -1175,6 +1201,7 @@ static inline void return_tx_buffer(VirtIOSoundPCMStream *stream,
>     virtqueue_push(buffer->vq,
>                    buffer->elem,
>                    sizeof(virtio_snd_pcm_status));
>+    stream->s->queue_inuse[VIRTIO_SND_VQ_TX] -= 1;

Ditto

>     virtio_notify(VIRTIO_DEVICE(stream->s), buffer->vq);
>     QSIMPLEQ_REMOVE(&stream->queue,
>                     buffer,
>@@ -1268,6 +1295,7 @@ static inline void return_rx_buffer(VirtIOSoundPCMStream *stream,
>     virtqueue_push(buffer->vq,
>                    buffer->elem,
>                    sizeof(virtio_snd_pcm_status) + buffer->size);
>+    stream->s->queue_inuse[VIRTIO_SND_VQ_RX] -= 1;

Ditto

>     virtio_notify(VIRTIO_DEVICE(stream->s), buffer->vq);
>     QSIMPLEQ_REMOVE(&stream->queue,
>                     buffer,
>@@ -1386,6 +1414,37 @@ static void virtio_snd_unrealize(DeviceState *dev)
>     virtio_cleanup(vdev);
> }
> 
>+static int virtio_snd_post_load(VirtIODevice *vdev)
>+{
>+    VirtIOSound *s = VIRTIO_SND(vdev);
>+    uint32_t i;
>+
>+    for (i = 0; i < s->snd_conf.streams; i++) {
>+        struct VirtIOSoundPCMStream *stream;
>+
>+        stream = virtio_snd_pcm_get_stream(s, i);
>+        if (stream->state & VSND_PCMSTREAM_STATE_F_PREPARED) {
>+            virtio_snd_pcm_open(stream);
>+
>+            if (stream->state & VSND_PCMSTREAM_STATE_F_ACTIVE) {
>+                virtio_snd_pcm_set_active(stream, true);
>+            }
>+        }
>+    }
>+
>+    for (i = 0; i < VIRTIO_SND_VQ_MAX; i++) {
>+        if (s->queue_inuse[i]) {
>+            if (!virtqueue_rewind(s->queues[i], s->queue_inuse[i])) {
>+                error_report(
>+                    "virtio-snd: could not rewind %u elements in queue %u",
>+                    s->queue_inuse[i], i);
>+            }
>+            s->queue_inuse[i] = 0;
>+        }
>+    }
>+
>+    return 0;
>+}
> 
> static void virtio_snd_reset(VirtIODevice *vdev)
> {
>@@ -1418,6 +1477,10 @@ static void virtio_snd_reset(VirtIODevice *vdev)
>             virtio_snd_pcm_buffer_free(buffer);
>         }
>     }
>+
>+    for (i = 0; i < VIRTIO_SND_VQ_MAX; i++) {
>+        vsnd->queue_inuse[i] = 0;
>+    }
> }
> 
> static void virtio_snd_class_init(ObjectClass *klass, const void *data)
>@@ -1431,6 +1494,7 @@ static void virtio_snd_class_init(ObjectClass *klass, const void *data)
> 
>     dc->vmsd = &vmstate_virtio_snd;
>     vdc->vmsd = &vmstate_virtio_snd_device;
>+    vdc->post_load = virtio_snd_post_load;
>     vdc->realize = virtio_snd_realize;
>     vdc->unrealize = virtio_snd_unrealize;
>     vdc->get_config = virtio_snd_get_config;
>diff --git a/include/hw/audio/virtio-snd.h b/include/hw/audio/virtio-snd.h
>index 85d5d7c8619..384d2868c19 100644
>--- a/include/hw/audio/virtio-snd.h
>+++ b/include/hw/audio/virtio-snd.h
>@@ -194,6 +194,7 @@ struct VirtIOSound {
>     VirtIODevice parent_obj;
> 
>     VirtQueue *queues[VIRTIO_SND_VQ_MAX];
>+    uint32_t queue_inuse[VIRTIO_SND_VQ_MAX];
>     uint64_t features;
>     VirtIOSoundPCMStream *streams;
>     AudioBackend *audio_be;
>-- 
>2.47.3
>