hw/virtio/virtio.c | 12 ++++++++++-- 1 file changed, 10 insertions(+), 2 deletions(-)
If a virtio-net device has the VIRTIO_NET_F_MRG_RXBUF feature
but not the VIRTIO_RING_F_INDIRECT_DESC feature,
'VirtIONetQueue->rx_vq' will use the merge feature
to store data in multiple 'elems'.
The 'num_buffers' in the virtio header indicates how many elements are merged.
If the value of 'num_buffers' is greater than 1,
all the merged elements will be filled into the descriptor ring.
The 'idx' of the elements should be the value of 'vq->used_idx' plus 'ndescs'.
Fixes: 86044b24e8 ("virtio: basic packed virtqueue support")
Signed-off-by: Wafer <wafer@jaguarmicro.com>
---
Changes in v3:
- Add the commit-ID of the introduced problem in commit message;
Changes in v2:
- Clarify more in commit message;
---
hw/virtio/virtio.c | 12 ++++++++++--
1 file changed, 10 insertions(+), 2 deletions(-)
diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c
index fb6b4ccd83..cab5832cac 100644
--- a/hw/virtio/virtio.c
+++ b/hw/virtio/virtio.c
@@ -957,12 +957,20 @@ static void virtqueue_packed_flush(VirtQueue *vq, unsigned int count)
return;
}
+ /*
+ * For indirect element's 'ndescs' is 1.
+ * For all other elemment's 'ndescs' is the
+ * number of descriptors chained by NEXT (as set in virtqueue_packed_pop).
+ * So When the 'elem' be filled into the descriptor ring,
+ * The 'idx' of this 'elem' shall be
+ * the value of 'vq->used_idx' plus the 'ndescs'.
+ */
+ ndescs += vq->used_elems[0].ndescs;
for (i = 1; i < count; i++) {
- virtqueue_packed_fill_desc(vq, &vq->used_elems[i], i, false);
+ virtqueue_packed_fill_desc(vq, &vq->used_elems[i], ndescs, false);
ndescs += vq->used_elems[i].ndescs;
}
virtqueue_packed_fill_desc(vq, &vq->used_elems[0], 0, true);
- ndescs += vq->used_elems[0].ndescs;
vq->inuse -= ndescs;
vq->used_idx += ndescs;
--
2.27.0
On Fri, Apr 5, 2024 at 3:20 PM Wafer <wafer@jaguarmicro.com> wrote: > > If a virtio-net device has the VIRTIO_NET_F_MRG_RXBUF feature > but not the VIRTIO_RING_F_INDIRECT_DESC feature, > 'VirtIONetQueue->rx_vq' will use the merge feature > to store data in multiple 'elems'. > The 'num_buffers' in the virtio header indicates how many elements are merged. > If the value of 'num_buffers' is greater than 1, > all the merged elements will be filled into the descriptor ring. > The 'idx' of the elements should be the value of 'vq->used_idx' plus 'ndescs'. > > Fixes: 86044b24e8 ("virtio: basic packed virtqueue support") Acked-by: Eugenio Pérez <eperezma@redhat.com> > Signed-off-by: Wafer <wafer@jaguarmicro.com> > > --- > Changes in v3: > - Add the commit-ID of the introduced problem in commit message; > > Changes in v2: > - Clarify more in commit message; > --- > hw/virtio/virtio.c | 12 ++++++++++-- > 1 file changed, 10 insertions(+), 2 deletions(-) > > diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c > index fb6b4ccd83..cab5832cac 100644 > --- a/hw/virtio/virtio.c > +++ b/hw/virtio/virtio.c > @@ -957,12 +957,20 @@ static void virtqueue_packed_flush(VirtQueue *vq, unsigned int count) > return; > } > > + /* > + * For indirect element's 'ndescs' is 1. > + * For all other elemment's 'ndescs' is the > + * number of descriptors chained by NEXT (as set in virtqueue_packed_pop). > + * So When the 'elem' be filled into the descriptor ring, > + * The 'idx' of this 'elem' shall be > + * the value of 'vq->used_idx' plus the 'ndescs'. > + */ > + ndescs += vq->used_elems[0].ndescs; > for (i = 1; i < count; i++) { > - virtqueue_packed_fill_desc(vq, &vq->used_elems[i], i, false); > + virtqueue_packed_fill_desc(vq, &vq->used_elems[i], ndescs, false); > ndescs += vq->used_elems[i].ndescs; > } > virtqueue_packed_fill_desc(vq, &vq->used_elems[0], 0, true); > - ndescs += vq->used_elems[0].ndescs; > > vq->inuse -= ndescs; > vq->used_idx += ndescs; > -- > 2.27.0 >
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