diff mbox series

[PULL,v3,11/41] hw/virtio: Fix obtain the buffer id from the last descriptor

Message ID acfb5cd252a78beb119d18878be1279e580e710c.1717630437.git.mst@redhat.com
State New
Headers show
Series [PULL,v3,01/41] vhost: dirty log should be per backend type | expand

Commit Message

Michael S. Tsirkin June 5, 2024, 11:35 p.m. UTC 
From: Wafer <wafer@jaguarmicro.com>

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>
---
 hw/virtio/virtio.c | 5 +++++
 1 file changed, 5 insertions(+)
diff mbox series

Patch

diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c
index 28cd406e16..3678ec2f88 100644
--- a/hw/virtio/virtio.c
+++ b/hw/virtio/virtio.c
@@ -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++) {