| Message ID | 20240404165706.23338-2-wafer@jaguarmicro.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [v2] hw/virtio: Fix packed virtqueue flush used_idx | expand |
On Thu, Apr 4, 2024 at 7:03 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'. > > Signed-off-by: Wafer <wafer@jaguarmicro.com> > Fixes: 86044b24e8 ("virtio: basic packed virtqueue support") ? > --- > 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); This bugged me recently when I was reviewing it for in_order feature implementation, thanks for the patch! Acked-by: Eugenio Pérez <eperezma@redhat.com> > 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 > >
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;
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'. Signed-off-by: Wafer <wafer@jaguarmicro.com> --- Changes in v2: - Clarify more in commit message; --- hw/virtio/virtio.c | 12 ++++++++++-- 1 file changed, 10 insertions(+), 2 deletions(-)