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hw/virtio: Fix obtain the buffer id from the last descriptor 

The virtio-1.3 specification
<https://docs.oasis-open.org/virtio/virtio/v1.3/virtio-v1.3.html> writes:
2.8.6 Next Flag: Descriptor Chaining
      Buffer ID is included in the last descriptor in the list.

If the feature (_F_INDIRECT_DESC) has been negotiated, install only
one descriptor in the virtqueue.
Therefor the buffer id should be obtained from the first descriptor.

In descriptor chaining scenarios, the buffer id should be obtained
from the last descriptor.

Fixes: 86044b24e8 ("virtio: basic packed virtqueue support")

Signed-off-by: Wafer <wafer@jaguarmicro.com>
Reviewed-by: Jason Wang <jasowang@redhat.com>
Reviewed-by: Eugenio Pérez <eperezma@redhat.com>
Acked-by: Jason Wang <jasowang@redhat.com>
Message-Id: <20240510072753.26158-2-wafer@jaguarmicro.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
This commit is contained in:
Wafer 2024-05-10 15:27:53 +08:00 committed by Michael S. Tsirkin
parent a0eebd790c
commit 33abfea239
1 changed files with 5 additions and 0 deletions
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5
hw/virtio/virtio.c
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@ -1745,6 +1745,11 @@ static void *virtqueue_packed_pop(VirtQueue *vq, size_t sz)
&indirect_desc_cache);
} while (rc == VIRTQUEUE_READ_DESC_MORE);
if (desc_cache != &indirect_desc_cache) {
/* Buffer ID is included in the last descriptor in the list. */
id = desc.id;
}
/* Now copy what we have collected and mapped */
elem = virtqueue_alloc_element(sz, out_num, in_num);
for (i = 0; i < out_num; i++) {