在 2022/2/17 下午8:48, Eugenio Perez Martin 写道:
On Tue, Feb 8, 2022 at 9:16 AM Jason Wang <jasowang@xxxxxxxxxx> wrote:
在 2022/2/1 下午7:25, Eugenio Perez Martin 写道:
On Sun, Jan 30, 2022 at 7:47 AM Jason Wang <jasowang@xxxxxxxxxx> wrote:
在 2022/1/22 上午4:27, Eugenio Pérez 写道:
@@ -272,6 +590,28 @@ void vhost_svq_set_svq_kick_fd(VhostShadowVirtqueue *svq, int svq_kick_fd)
void vhost_svq_stop(VhostShadowVirtqueue *svq)
{
event_notifier_set_handler(&svq->svq_kick, NULL);
+ g_autofree VirtQueueElement *next_avail_elem = NULL;
+
+ if (!svq->vq) {
+ return;
+ }
+
+ /* Send all pending used descriptors to guest */
+ vhost_svq_flush(svq, false);
Do we need to wait for all the pending descriptors to be completed here?
No, this function does not wait, it only completes the forwarding of
the *used* descriptors.
The best example is the net rx queue in my opinion. This call will
check SVQ's vring used_idx and will forward the last used descriptors
if any, but all available descriptors will remain as available for
qemu's VQ code.
To skip it would miss those last rx descriptors in migration.
Thanks!
So it's probably to not the best place to ask. It's more about the
inflight descriptors so it should be TX instead of RX.
I can imagine the migration last phase, we should stop the vhost-vDPA
before calling vhost_svq_stop(). Then we should be fine regardless of
inflight descriptors.
I think I'm still missing something here.
To be on the same page. Regarding tx this could cause repeated tx
frames (one at source and other at destination), but never a missed
buffer not transmitted. The "stop before" could be interpreted as "SVQ
is not forwarding available buffers anymore". Would that work?
Right, but this only work if
1) a flush to make sure TX DMA for inflight descriptors are all completed
2) just mark all inflight descriptor used
Otherwise there could be buffers that is inflight forever.
Thanks
Thanks!
Thanks
Thanks
+
+ for (unsigned i = 0; i < svq->vring.num; ++i) {
+ g_autofree VirtQueueElement *elem = NULL;
+ elem = g_steal_pointer(&svq->ring_id_maps[i]);
+ if (elem) {
+ virtqueue_detach_element(svq->vq, elem, elem->len);
+ }
+ }
+
+ next_avail_elem = g_steal_pointer(&svq->next_guest_avail_elem);
+ if (next_avail_elem) {
+ virtqueue_detach_element(svq->vq, next_avail_elem,
+ next_avail_elem->len);
+ }
}
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