From: Wafer <wafer@jaguarmicro.com>
To: mst@redhat.com
Cc: eperezma@redhat.com, jasowang@redhat.com, qemu-devel@nongnu.org,
angus.chen@jaguarmicro.com, Wafer <wafer@jaguarmicro.com>
Subject: [PATCH v2] hw/virtio: Fix obtain the buffer id from the last descriptor
Date: Thu, 9 May 2024 19:45:52 +0800 [thread overview]
Message-ID: <20240509114552.11525-2-wafer@jaguarmicro.com> (raw)
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>
--
Changes in v2:
- Use Jason suggestion: Move the code out of the loop.
---
hw/virtio/virtio.c | 5 +++++
1 file changed, 5 insertions(+)
diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c
index 871674f9be..e9e8447878 100644
--- a/hw/virtio/virtio.c
+++ b/hw/virtio/virtio.c
@@ -1744,6 +1744,11 @@ 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++) {
--
2.27.0
reply other threads:[~2024-05-09 11:48 UTC|newest]
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