On 2026/08/18 14:12, Connor Kite wrote:
Adds a callback to shadow virtqueues in order to enable
non-default processing of used vring elements from the device.
Signed-off-by: Connor Kite <[email protected]>
---
hw/virtio/vhost-shadow-virtqueue.c | 9 +++++++++
hw/virtio/vhost-shadow-virtqueue.h | 16 ++++++++++++++++
2 files changed, 25 insertions(+)
diff --git a/hw/virtio/vhost-shadow-virtqueue.c
b/hw/virtio/vhost-shadow-virtqueue.c
index c8831d52be..496e7e58a3 100644
--- a/hw/virtio/vhost-shadow-virtqueue.c
+++ b/hw/virtio/vhost-shadow-virtqueue.c
@@ -675,6 +675,15 @@ static void vhost_svq_flush(VhostShadowVirtqueue *svq,
break;
}
+ if (svq->ops && svq->ops->used_callback) {
+ int r = svq->ops->used_callback(svq, elem, svq->ops_opaque);
+
+ if (r < 0) {
+ /* VQ or handler is broken. Do not set guest notifier */
This comment is extraneous. It is obvious that event_notifier_set()
below is not called, and it is same with the existing error path below.
What matters here is the difference with the existing error path. Why
doesn't it call virtqueue_fill() nor virtqueue_flush()? They need to be
addressed here.
Regards,
Akihiko Odaki
+ return;
+ }
+ }
+
if (unlikely(i >= svq->vring.num)) {
qemu_log_mask(LOG_GUEST_ERROR,
"More than %u used buffers obtained in a %u size
SVQ",
diff --git a/hw/virtio/vhost-shadow-virtqueue.h
b/hw/virtio/vhost-shadow-virtqueue.h
index ec16a1e838..fd68319fb7 100644
--- a/hw/virtio/vhost-shadow-virtqueue.h
+++ b/hw/virtio/vhost-shadow-virtqueue.h
@@ -56,8 +56,24 @@ typedef int (*VirtQueueAvailCallback)(VhostShadowVirtqueue
*svq,
VirtQueueElement *elem,
void *vq_callback_opaque);
+/**
+ * Callback to handle a used buffer
+ *
+ * @svq: Shadow virtqueue
+ * @elem: Element placed in the queue by the device
+ * @vq_callback_opaque: Used to pass arguments to callback
+ *
+ * Returns 0 if the vq is running as expected. Returns a negative errno on
+ * failure. The callback should not add used elements to the vq shadowed
+ * by the svq as that is done separately after the callback returns.
+ */
+typedef int (*VirtQueueUsedCallback)(VhostShadowVirtqueue *svq,
+ VirtQueueElement *elem,
+ void *vq_callback_opaque);
+
typedef struct VhostShadowVirtqueueOps {
VirtQueueAvailCallback avail_handler;
+ VirtQueueUsedCallback used_callback;
} VhostShadowVirtqueueOps;
/* Shadow virtqueue to relay notifications */
