[dpdk-dev] [PATCH] vhost: fix invalid use of stored last used index
Maxime Coquelin
maxime.coquelin at redhat.com
Mon May 17 09:37:39 CEST 2021
Hi Ling,
On 5/14/21 6:02 PM, Balazs Nemeth wrote:
> The optimization introduced by commit d18db8049c7c ("vhost: read last
> used index once") didn't account for the fact that
> vhost_flush_enqueue_shadow_packed increments the last_used_idx. For this
> reason, store last_used_idx after the potential call to
> vhost_flush_enqueue_shadow_packed.
>
> Fixes: d18db8049c7c ("vhost: read last used index once")
> Signed-off-by: Balazs Nemeth <bnemeth at redhat.com>
> ---
> lib/vhost/virtio_net.c | 7 +++++--
> 1 file changed, 5 insertions(+), 2 deletions(-)
>
> diff --git a/lib/vhost/virtio_net.c b/lib/vhost/virtio_net.c
> index abfd67d38c..8da8a86a10 100644
> --- a/lib/vhost/virtio_net.c
> +++ b/lib/vhost/virtio_net.c
> @@ -218,14 +218,17 @@ vhost_flush_enqueue_batch_packed(struct virtio_net *dev,
> {
> uint16_t i;
> uint16_t flags;
> - uint16_t last_used_idx = vq->last_used_idx;
> - struct vring_packed_desc *desc_base = &vq->desc_packed[last_used_idx];
> + uint16_t last_used_idx;
> + struct vring_packed_desc *desc_base;
>
> if (vq->shadow_used_idx) {
> do_data_copy_enqueue(dev, vq);
> vhost_flush_enqueue_shadow_packed(dev, vq);
> }
>
> + last_used_idx = vq->last_used_idx;
> + desc_base = &vq->desc_packed[last_used_idx];
> +
> flags = PACKED_DESC_ENQUEUE_USED_FLAG(vq->used_wrap_counter);
>
> vhost_for_each_try_unroll(i, 0, PACKED_BATCH_SIZE) {
>
Could you please confirm the patch fixes the issue you reported?
Thanks,
Maxime
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