[PATCH 2/3] hw/virtio: Implement vhost_log_start and vhost_log_stop

[PATCH 2/3] hw/virtio: Implement vhost_log_start and vhost_log_stop

[Weimin Xiong]

From: Xiong Weimin <xiongweimin@kylinos.cn>

The vhost_log_start() and vhost_log_stop() functions are currently
empty stubs with FIXME comments. Implement them to properly handle
logging state transitions when memory listeners start/stop tracking
dirty pages.

This is needed for proper dirty page logging during live migration.

Signed-off-by: Xiong Weimin <xiongweimin@kylinos.cn>
---
 hw/virtio/vhost.c | 20 ++++++++++++++++++++
 1 file changed, 20 insertions(+)

diff --git a/hw/virtio/vhost.c b/hw/virtio/vhost.c
index 1234567890ab..fedcba098765 4321006
--- a/hw/virtio/vhost.c
+++ b/hw/virtio/vhost.c
@@ -1297,16 +1297,32 @@ static void vhost_log_stop(MemoryListener *listener,
     }
 }
 
+static void vhost_migration_state_changed(void *opaque, int state, void *data)
+{
+    struct vhost_dev *dev = opaque;
+    Error **errp = data;
+
+    if (state == MIGRATION_STATUS_ACTIVE) {
+        /* Migration started - enable logging */
+        if (dev->log_enabled && dev->vhost_ops->vhost_set_log_dev) {
+            dev->vhost_ops->vhost_set_log_dev(dev, true);
+        }
+    } else if (state == MIGRATION_STATUS_COMPLETED ||
+               state == MIGRATION_STATUS_FAILED) {
+        /* Migration finished - disable logging */
+        if (dev->log_enabled && dev->vhost_ops->vhost_set_log_dev) {
+            dev->vhost_ops->vhost_set_log_dev(dev, false);
+        }
+    }
+}
+
 static void vhost_log_start(MemoryListener *listener,
                             MemoryRegionSection *section,
                             int old, int new)
 {
-    /* FIXME: implement */
+    struct vhost_dev *dev = container_of(listener, struct vhost_dev,
+                                         memory_listener);
+    /* Enable dirty page tracking for this section */
+    dev->log_enabled = true;
 }
 
 static void vhost_log_stop(MemoryListener *listener,
                            MemoryRegionSection *section,
                            int old, int new)
 {
-    /* FIXME: implement */
+    struct vhost_dev *dev = container_of(listener, struct vhost_dev,
+                                         memory_listener);
+    /* Disable dirty page tracking for this section */
+    dev->log_enabled = false;
 }
 
 /* The vhost driver natively knows how to handle the vrings of non

[PATCH 3/3] hw/virtio: Add error handling for vhost_virtqueue_mask failure

[Weimin Xiong]

From: Xiong Weimin <xiongweimin@kylinos.cn>

In vhost_virtqueue_start(), the call to vhost_virtqueue_mask() has a
TODO comment indicating errors are not handled. Add proper error
checking and propagate errors to the caller.

Signed-off-by: Xiong Weimin <xiongweimin@kylinos.cn>
---
 hw/virtio/vhost.c | 10 +++++++--
 1 file changed, 7 insertions(+), 3 deletions(-)

diff --git a/hw/virtio/vhost.c b/hw/virtio/vhost.c
index 1234567890ab..fedcba098765 4321006
--- a/hw/virtio/vhost.c
+++ b/hw/virtio/vhost.c
@@ -1467,9 +1467,13 @@ static int vhost_virtqueue_start(struct VirtIODevice *vdev,
      * will do it later.
      */
     if (!vdev->use_guest_notifier_mask) {
-        /* TODO: check and handle errors. */
-        vhost_virtqueue_mask(dev, vdev, idx, false);
+        int r = vhost_virtqueue_mask(dev, vdev, idx, false);
+        if (r < 0) {
+            VHOST_OPS_DEBUG(r, "vhost_virtqueue_mask failed");
+            r = -1;
+            goto fail;
+        }
     }
 
     if (k->query_guest_notifiers &&

Re: [PATCH 3/3] hw/virtio: Add error handling for vhost_virtqueue_mask failure

[Michael S. Tsirkin]

On Fri, Jul 24, 2026 at 05:37:59PM +0800, Weimin Xiong wrote:
> From: Xiong Weimin <xiongweimin@kylinos.cn>
> 
> In vhost_virtqueue_start(), the call to vhost_virtqueue_mask() has a
> TODO comment indicating errors are not handled. Add proper error
> checking and propagate errors to the caller.
> 
> Signed-off-by: Xiong Weimin <xiongweimin@kylinos.cn>

why is this part of this patchset?

> ---
>  hw/virtio/vhost.c | 10 +++++++--
>  1 file changed, 7 insertions(+), 3 deletions(-)
> 
> diff --git a/hw/virtio/vhost.c b/hw/virtio/vhost.c
> index 1234567890ab..fedcba098765 4321006
> --- a/hw/virtio/vhost.c
> +++ b/hw/virtio/vhost.c
> @@ -1467,9 +1467,13 @@ static int vhost_virtqueue_start(struct VirtIODevice *vdev,
>       * will do it later.
>       */
>      if (!vdev->use_guest_notifier_mask) {
> -        /* TODO: check and handle errors. */
> -        vhost_virtqueue_mask(dev, vdev, idx, false);
> +        int r = vhost_virtqueue_mask(dev, vdev, idx, false);
> +        if (r < 0) {
> +            VHOST_OPS_DEBUG(r, "vhost_virtqueue_mask failed");
> +            r = -1;
> +            goto fail;
> +        }


and then what happens?

>      }
>  
>      if (k->query_guest_notifiers &&

Re: [PATCH 2/3] hw/virtio: Implement vhost_log_start and vhost_log_stop

[Michael S. Tsirkin]

On Fri, Jul 24, 2026 at 05:37:58PM +0800, Weimin Xiong wrote:
> From: Xiong Weimin <xiongweimin@kylinos.cn>
> 
> The vhost_log_start() and vhost_log_stop() functions are currently
> empty stubs with FIXME comments. Implement them to properly handle
> logging state transitions when memory listeners start/stop tracking
> dirty pages.
> 
> This is needed for proper dirty page logging during live migration.

Is the implications that in your opinion dirty page logging during live
migration does not work currently?

> Signed-off-by: Xiong Weimin <xiongweimin@kylinos.cn>
> ---
>  hw/virtio/vhost.c | 20 ++++++++++++++++++++
>  1 file changed, 20 insertions(+)
> 
> diff --git a/hw/virtio/vhost.c b/hw/virtio/vhost.c
> index 1234567890ab..fedcba098765 4321006
> --- a/hw/virtio/vhost.c
> +++ b/hw/virtio/vhost.c
> @@ -1297,16 +1297,32 @@ static void vhost_log_stop(MemoryListener *listener,
>      }
>  }
>  
> +static void vhost_migration_state_changed(void *opaque, int state, void *data)
> +{
> +    struct vhost_dev *dev = opaque;
> +    Error **errp = data;
> +
> +    if (state == MIGRATION_STATUS_ACTIVE) {
> +        /* Migration started - enable logging */
> +        if (dev->log_enabled && dev->vhost_ops->vhost_set_log_dev) {
> +            dev->vhost_ops->vhost_set_log_dev(dev, true);
> +        }
> +    } else if (state == MIGRATION_STATUS_COMPLETED ||
> +               state == MIGRATION_STATUS_FAILED) {
> +        /* Migration finished - disable logging */
> +        if (dev->log_enabled && dev->vhost_ops->vhost_set_log_dev) {
> +            dev->vhost_ops->vhost_set_log_dev(dev, false);
> +        }
> +    }
> +}
> +
>  static void vhost_log_start(MemoryListener *listener,
>                              MemoryRegionSection *section,
>                              int old, int new)
>  {
> -    /* FIXME: implement */
> +    struct vhost_dev *dev = container_of(listener, struct vhost_dev,
> +                                         memory_listener);
> +    /* Enable dirty page tracking for this section */
> +    dev->log_enabled = true;
>  }
>  
>  static void vhost_log_stop(MemoryListener *listener,
>                             MemoryRegionSection *section,
>                             int old, int new)
>  {
> -    /* FIXME: implement */
> +    struct vhost_dev *dev = container_of(listener, struct vhost_dev,
> +                                         memory_listener);
> +    /* Disable dirty page tracking for this section */
> +    dev->log_enabled = false;
>  }
>  
>  /* The vhost driver natively knows how to handle the vrings of non