Re: [PATCH vhost] virtio_net: fix the missing of the dma cpu sync

[Jason Wang]

On Wed, Sep 27, 2023 at 1:53 PM Xuan Zhuo  wrote:
>
> Commit 295525e29a5b ("virtio_net: merge dma operations when filling
> mergeable buffers") unmaps the buffer with DMA_ATTR_SKIP_CPU_SYNC when
> the dma->ref is zero. We do that with DMA_ATTR_SKIP_CPU_SYNC, because we
> do not want to do the sync for the entire page_frag. But that misses the
> sync for the current area.
>
> This patch does cpu sync regardless of whether the ref is zero or not.
>
> Fixes: 295525e29a5b ("virtio_net: merge dma operations when filling mergeable 
> buffers")
> Reported-by: Michael Roth 
> Closes: http://lore.kernel.org/all/20230926130451.axgodaa6tvwqs...@amd.com
> Signed-off-by: Xuan Zhuo 

Acked-by: Jason Wang 

Thanks

> ---
>  drivers/net/virtio_net.c | 14 +++---
>  1 file changed, 7 insertions(+), 7 deletions(-)
>
> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> index 98dc9b49d56b..9ece27dc5144 100644
> --- a/drivers/net/virtio_net.c
> +++ b/drivers/net/virtio_net.c
> @@ -589,16 +589,16 @@ static void virtnet_rq_unmap(struct receive_queue *rq, 
> void *buf, u32 len)
>
> --dma->ref;
>
> -   if (dma->ref) {
> -   if (dma->need_sync && len) {
> -   offset = buf - (head + sizeof(*dma));
> +   if (dma->need_sync && len) {
> +   offset = buf - (head + sizeof(*dma));
>
> -   virtqueue_dma_sync_single_range_for_cpu(rq->vq, 
> dma->addr, offset,
> -   len, 
> DMA_FROM_DEVICE);
> -   }
> +   virtqueue_dma_sync_single_range_for_cpu(rq->vq, dma->addr,
> +   offset, len,
> +   DMA_FROM_DEVICE);
> +   }
>
> +   if (dma->ref)
> return;
> -   }
>
> virtqueue_dma_unmap_single_attrs(rq->vq, dma->addr, dma->len,
>  DMA_FROM_DEVICE, 
> DMA_ATTR_SKIP_CPU_SYNC);
> --
> 2.32.0.3.g01195cf9f
>
>

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[PATCH vhost] virtio_net: fix the missing of the dma cpu sync

[Xuan Zhuo]

Commit 295525e29a5b ("virtio_net: merge dma operations when filling
mergeable buffers") unmaps the buffer with DMA_ATTR_SKIP_CPU_SYNC when
the dma->ref is zero. We do that with DMA_ATTR_SKIP_CPU_SYNC, because we
do not want to do the sync for the entire page_frag. But that misses the
sync for the current area.

This patch does cpu sync regardless of whether the ref is zero or not.

Fixes: 295525e29a5b ("virtio_net: merge dma operations when filling mergeable 
buffers")
Reported-by: Michael Roth 
Closes: http://lore.kernel.org/all/20230926130451.axgodaa6tvwqs...@amd.com
Signed-off-by: Xuan Zhuo 
---
 drivers/net/virtio_net.c | 14 +++---
 1 file changed, 7 insertions(+), 7 deletions(-)

diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index 98dc9b49d56b..9ece27dc5144 100644
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c
@@ -589,16 +589,16 @@ static void virtnet_rq_unmap(struct receive_queue *rq, 
void *buf, u32 len)
 
--dma->ref;
 
-   if (dma->ref) {
-   if (dma->need_sync && len) {
-   offset = buf - (head + sizeof(*dma));
+   if (dma->need_sync && len) {
+   offset = buf - (head + sizeof(*dma));
 
-   virtqueue_dma_sync_single_range_for_cpu(rq->vq, 
dma->addr, offset,
-   len, 
DMA_FROM_DEVICE);
-   }
+   virtqueue_dma_sync_single_range_for_cpu(rq->vq, dma->addr,
+   offset, len,
+   DMA_FROM_DEVICE);
+   }
 
+   if (dma->ref)
return;
-   }
 
virtqueue_dma_unmap_single_attrs(rq->vq, dma->addr, dma->len,
 DMA_FROM_DEVICE, 
DMA_ATTR_SKIP_CPU_SYNC);
-- 
2.32.0.3.g01195cf9f

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