Re: [PATCH v5 02/10] vhost: use SVQ element ndescs instead of opaque data for desc validation

[Jason Wang]

在 2022/8/3 01:57, Eugenio Pérez 写道:

Since we're going to allow SVQ to add elements without the guest's
knowledge and without its own VirtQueueElement, it's easier to check if
an element is a valid head checking a different thing than the
VirtQueueElement.

Signed-off-by: Eugenio Pérez <epere...@redhat.com>
---

Patch looks good to me. But I spot several other issues:

1) vhost_svq_add() use size_t for in_num and out_num, is this intended?
2) do we need to fail vhost_svq_add() if in_num + out_num == 0?

Thanks

  hw/virtio/vhost-shadow-virtqueue.c | 3 ++-
  1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/hw/virtio/vhost-shadow-virtqueue.c 
b/hw/virtio/vhost-shadow-virtqueue.c
index ffd2b2c972..e6eebd0e8d 100644
--- a/hw/virtio/vhost-shadow-virtqueue.c
+++ b/hw/virtio/vhost-shadow-virtqueue.c
@@ -414,7 +414,7 @@ static VirtQueueElement 
*vhost_svq_get_buf(VhostShadowVirtqueue *svq,
          return NULL;
      }

- if (unlikely(!svq->desc_state[used_elem.id].elem)) {

+    if (unlikely(!svq->desc_state[used_elem.id].ndescs)) {
          qemu_log_mask(LOG_GUEST_ERROR,
              "Device %s says index %u is used, but it was not available",
              svq->vdev->name, used_elem.id);
@@ -422,6 +422,7 @@ static VirtQueueElement 
*vhost_svq_get_buf(VhostShadowVirtqueue *svq,
      }

num = svq->desc_state[used_elem.id].ndescs;

+    svq->desc_state[used_elem.id].ndescs = 0;
      last_used_chain = vhost_svq_last_desc_of_chain(svq, num, used_elem.id);
      svq->desc_next[last_used_chain] = svq->free_head;
      svq->free_head = used_elem.id;