[PATCH v2] virtio_net: Fix mismatched buf address when unmapping for small packets

[PATCH v2] virtio_net: Fix mismatched buf address when unmapping for small packets

[Wenbo Li]

Currently, the virtio-net driver will perform a pre-dma-mapping for
small or mergeable RX buffer. But for small packets, a mismatched address
without VIRTNET_RX_PAD and xdp_headroom is used for unmapping.

That will result in unsynchronized buffers when SWIOTLB is enabled, for
example, when running as a TDX guest.

This patch handles small and mergeable packets separately and fixes
the mismatched buffer address.

Changes from v1: Use ctx to get xdp_headroom.

Fixes: 295525e29a5b ("virtio_net: merge dma operations when filling mergeable buffers")
Signed-off-by: Wenbo Li <liwenbo.martin@bytedance.com>
Signed-off-by: Jiahui Cen <cenjiahui@bytedance.com>
Signed-off-by: Ying Fang <fangying.tommy@bytedance.com>
---
 drivers/net/virtio_net.c | 29 ++++++++++++++++++++++++++++-
 1 file changed, 28 insertions(+), 1 deletion(-)

diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index c6af18948..cbc3c0ae4 100644
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c
@@ -891,6 +891,23 @@ static void *virtnet_rq_get_buf(struct receive_queue *rq, u32 *len, void **ctx)
 	return buf;
 }
 
+static void *virtnet_rq_get_buf_small(struct receive_queue *rq,
+				      u32 *len,
+				      void **ctx,
+				      unsigned int header_offset)
+{
+	void *buf;
+	unsigned int xdp_headroom;
+
+	buf = virtqueue_get_buf_ctx(rq->vq, len, ctx);
+	if (buf) {
+		xdp_headroom = (unsigned long)*ctx;
+		virtnet_rq_unmap(rq, buf + VIRTNET_RX_PAD + xdp_headroom, *len);
+	}
+
+	return buf;
+}
+
 static void virtnet_rq_init_one_sg(struct receive_queue *rq, void *buf, u32 len)
 {
 	struct virtnet_rq_dma *dma;
@@ -2692,13 +2709,23 @@ static int virtnet_receive_packets(struct virtnet_info *vi,
 	int packets = 0;
 	void *buf;
 
-	if (!vi->big_packets || vi->mergeable_rx_bufs) {
+	if (vi->mergeable_rx_bufs) {
 		void *ctx;
 		while (packets < budget &&
 		       (buf = virtnet_rq_get_buf(rq, &len, &ctx))) {
 			receive_buf(vi, rq, buf, len, ctx, xdp_xmit, stats);
 			packets++;
 		}
+	} else if (!vi->big_packets) {
+		void *ctx;
+		unsigned int xdp_headroom = virtnet_get_headroom(vi);
+		unsigned int header_offset = VIRTNET_RX_PAD + xdp_headroom;
+
+		while (packets < budget &&
+		       (buf = virtnet_rq_get_buf_small(rq, &len, &ctx, header_offset))) {
+			receive_buf(vi, rq, buf, len, ctx, xdp_xmit, stats);
+			packets++;
+		}
 	} else {
 		while (packets < budget &&
 		       (buf = virtqueue_get_buf(rq->vq, &len)) != NULL) {
-- 
2.20.1

Re: [PATCH v2] virtio_net: Fix mismatched buf address when unmapping for small packets

[Jason Wang]

On Wed, Sep 4, 2024 at 2:10 PM Wenbo Li <liwenbo.martin@bytedance.com> wrote:
>
> Currently, the virtio-net driver will perform a pre-dma-mapping for
> small or mergeable RX buffer. But for small packets, a mismatched address
> without VIRTNET_RX_PAD and xdp_headroom is used for unmapping.
>
> That will result in unsynchronized buffers when SWIOTLB is enabled, for
> example, when running as a TDX guest.
>
> This patch handles small and mergeable packets separately and fixes
> the mismatched buffer address.
>
> Changes from v1: Use ctx to get xdp_headroom.
>
> Fixes: 295525e29a5b ("virtio_net: merge dma operations when filling mergeable buffers")
> Signed-off-by: Wenbo Li <liwenbo.martin@bytedance.com>
> Signed-off-by: Jiahui Cen <cenjiahui@bytedance.com>
> Signed-off-by: Ying Fang <fangying.tommy@bytedance.com>
> ---
>  drivers/net/virtio_net.c | 29 ++++++++++++++++++++++++++++-
>  1 file changed, 28 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> index c6af18948..cbc3c0ae4 100644
> --- a/drivers/net/virtio_net.c
> +++ b/drivers/net/virtio_net.c
> @@ -891,6 +891,23 @@ static void *virtnet_rq_get_buf(struct receive_queue *rq, u32 *len, void **ctx)
>         return buf;
>  }
>
> +static void *virtnet_rq_get_buf_small(struct receive_queue *rq,
> +                                     u32 *len,
> +                                     void **ctx,
> +                                     unsigned int header_offset)

header_offset is unused?

> +{
> +       void *buf;
> +       unsigned int xdp_headroom;
> +
> +       buf = virtqueue_get_buf_ctx(rq->vq, len, ctx);
> +       if (buf) {
> +               xdp_headroom = (unsigned long)*ctx;
> +               virtnet_rq_unmap(rq, buf + VIRTNET_RX_PAD + xdp_headroom, *len);
> +       }
> +
> +       return buf;
> +}
> +
>  static void virtnet_rq_init_one_sg(struct receive_queue *rq, void *buf, u32 len)
>  {
>         struct virtnet_rq_dma *dma;
> @@ -2692,13 +2709,23 @@ static int virtnet_receive_packets(struct virtnet_info *vi,
>         int packets = 0;
>         void *buf;
>
> -       if (!vi->big_packets || vi->mergeable_rx_bufs) {
> +       if (vi->mergeable_rx_bufs) {
>                 void *ctx;
>                 while (packets < budget &&
>                        (buf = virtnet_rq_get_buf(rq, &len, &ctx))) {
>                         receive_buf(vi, rq, buf, len, ctx, xdp_xmit, stats);
>                         packets++;
>                 }
> +       } else if (!vi->big_packets) {
> +               void *ctx;
> +               unsigned int xdp_headroom = virtnet_get_headroom(vi);
> +               unsigned int header_offset = VIRTNET_RX_PAD + xdp_headroom;
> +
> +               while (packets < budget &&
> +                      (buf = virtnet_rq_get_buf_small(rq, &len, &ctx, header_offset))) {
> +                       receive_buf(vi, rq, buf, len, ctx, xdp_xmit, stats);
> +                       packets++;
> +               }
>         } else {
>                 while (packets < budget &&
>                        (buf = virtqueue_get_buf(rq->vq, &len)) != NULL) {
> --
> 2.20.1
>

Thanks

Re: [PATCH v2] virtio_net: Fix mismatched buf address when unmapping for small packets

[Xuan Zhuo]

On Wed,  4 Sep 2024 14:10:09 +0800, Wenbo Li <liwenbo.martin@bytedance.com> wrote:
> Currently, the virtio-net driver will perform a pre-dma-mapping for
> small or mergeable RX buffer. But for small packets, a mismatched address
> without VIRTNET_RX_PAD and xdp_headroom is used for unmapping.

Will used virt_to_head_page(), so could you say more about it?

	struct page *page = virt_to_head_page(buf);

Thanks.

>
> That will result in unsynchronized buffers when SWIOTLB is enabled, for
> example, when running as a TDX guest.
>
> This patch handles small and mergeable packets separately and fixes
> the mismatched buffer address.
>
> Changes from v1: Use ctx to get xdp_headroom.
>
> Fixes: 295525e29a5b ("virtio_net: merge dma operations when filling mergeable buffers")
> Signed-off-by: Wenbo Li <liwenbo.martin@bytedance.com>
> Signed-off-by: Jiahui Cen <cenjiahui@bytedance.com>
> Signed-off-by: Ying Fang <fangying.tommy@bytedance.com>
> ---
>  drivers/net/virtio_net.c | 29 ++++++++++++++++++++++++++++-
>  1 file changed, 28 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> index c6af18948..cbc3c0ae4 100644
> --- a/drivers/net/virtio_net.c
> +++ b/drivers/net/virtio_net.c
> @@ -891,6 +891,23 @@ static void *virtnet_rq_get_buf(struct receive_queue *rq, u32 *len, void **ctx)
>  	return buf;
>  }
>
> +static void *virtnet_rq_get_buf_small(struct receive_queue *rq,
> +				      u32 *len,
> +				      void **ctx,
> +				      unsigned int header_offset)
> +{
> +	void *buf;
> +	unsigned int xdp_headroom;
> +
> +	buf = virtqueue_get_buf_ctx(rq->vq, len, ctx);
> +	if (buf) {
> +		xdp_headroom = (unsigned long)*ctx;
> +		virtnet_rq_unmap(rq, buf + VIRTNET_RX_PAD + xdp_headroom, *len);
> +	}
> +
> +	return buf;
> +}
> +
>  static void virtnet_rq_init_one_sg(struct receive_queue *rq, void *buf, u32 len)
>  {
>  	struct virtnet_rq_dma *dma;
> @@ -2692,13 +2709,23 @@ static int virtnet_receive_packets(struct virtnet_info *vi,
>  	int packets = 0;
>  	void *buf;
>
> -	if (!vi->big_packets || vi->mergeable_rx_bufs) {
> +	if (vi->mergeable_rx_bufs) {
>  		void *ctx;
>  		while (packets < budget &&
>  		       (buf = virtnet_rq_get_buf(rq, &len, &ctx))) {
>  			receive_buf(vi, rq, buf, len, ctx, xdp_xmit, stats);
>  			packets++;
>  		}
> +	} else if (!vi->big_packets) {
> +		void *ctx;
> +		unsigned int xdp_headroom = virtnet_get_headroom(vi);
> +		unsigned int header_offset = VIRTNET_RX_PAD + xdp_headroom;
> +
> +		while (packets < budget &&
> +		       (buf = virtnet_rq_get_buf_small(rq, &len, &ctx, header_offset))) {
> +			receive_buf(vi, rq, buf, len, ctx, xdp_xmit, stats);
> +			packets++;
> +		}
>  	} else {
>  		while (packets < budget &&
>  		       (buf = virtqueue_get_buf(rq->vq, &len)) != NULL) {
> --
> 2.20.1
>

Re: [External] Re: [PATCH v2] virtio_net: Fix mismatched buf address when unmapping for small packets

[Xuan Zhuo]

On Wed, 4 Sep 2024 15:21:28 +0800, =?utf-8?b?5paH5Y2a5p2O?= <liwenbo.martin@bytedance.com> wrote:
> When SWIOTLB is enabled, a DMA map will allocate a bounce buffer for real
> DMA operations,
> and when unmapping, SWIOTLB copies the content in the bounce buffer to the
> driver-allocated
> buffer (the `buf` variable). Such copy only synchronizes data in the buffer
> range, not the whole page.
> So we should give the correct offset for DMA unmapping.

I see.

But I think we should pass the "correct" buf to virtio core as the "data" by
virtqueue_add_inbuf_ctx().

In the merge mode, we pass the pointer that points to the virtnet header.
In the small mode, we pass the pointer that points to the virtnet header - offset.

But this is not the only problem, we try to get the virtnet header by the buf
inside receive_buf(before receive_small).

	flags = ((struct virtio_net_common_hdr *)buf)->hdr.flags;

So I think it is time to unify the buf that passed to the virtio core into a
pointer pointed to the virtnet header.

Thanks.


>
> Thanks.
>
> On Wed, Sep 4, 2024 at 2:46 PM Xuan Zhuo <xuanzhuo@linux.alibaba.com> wrote:
> >
> > On Wed,  4 Sep 2024 14:10:09 +0800, Wenbo Li <liwenbo.martin@bytedance.com>
> wrote:
> > > Currently, the virtio-net driver will perform a pre-dma-mapping for
> > > small or mergeable RX buffer. But for small packets, a mismatched
> address
> > > without VIRTNET_RX_PAD and xdp_headroom is used for unmapping.
> >
> > Will used virt_to_head_page(), so could you say more about it?
> >
> >         struct page *page = virt_to_head_page(buf);
> >
> > Thanks.
> >
> > >
> > > That will result in unsynchronized buffers when SWIOTLB is enabled, for
> > > example, when running as a TDX guest.
> > >
> > > This patch handles small and mergeable packets separately and fixes
> > > the mismatched buffer address.
> > >
> > > Changes from v1: Use ctx to get xdp_headroom.
> > >
> > > Fixes: 295525e29a5b ("virtio_net: merge dma operations when filling
> mergeable buffers")
> > > Signed-off-by: Wenbo Li <liwenbo.martin@bytedance.com>
> > > Signed-off-by: Jiahui Cen <cenjiahui@bytedance.com>
> > > Signed-off-by: Ying Fang <fangying.tommy@bytedance.com>
> > > ---
> > >  drivers/net/virtio_net.c | 29 ++++++++++++++++++++++++++++-
> > >  1 file changed, 28 insertions(+), 1 deletion(-)
> > >
> > > diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> > > index c6af18948..cbc3c0ae4 100644
> > > --- a/drivers/net/virtio_net.c
> > > +++ b/drivers/net/virtio_net.c
> > > @@ -891,6 +891,23 @@ static void *virtnet_rq_get_buf(struct
> receive_queue *rq, u32 *len, void **ctx)
> > >       return buf;
> > >  }
> > >
> > > +static void *virtnet_rq_get_buf_small(struct receive_queue *rq,
> > > +                                   u32 *len,
> > > +                                   void **ctx,
> > > +                                   unsigned int header_offset)
> > > +{
> > > +     void *buf;
> > > +     unsigned int xdp_headroom;
> > > +
> > > +     buf = virtqueue_get_buf_ctx(rq->vq, len, ctx);
> > > +     if (buf) {
> > > +             xdp_headroom = (unsigned long)*ctx;
> > > +             virtnet_rq_unmap(rq, buf + VIRTNET_RX_PAD + xdp_headroom,
> *len);
> > > +     }
> > > +
> > > +     return buf;
> > > +}
> > > +
> > >  static void virtnet_rq_init_one_sg(struct receive_queue *rq, void
> *buf, u32 len)
> > >  {
> > >       struct virtnet_rq_dma *dma;
> > > @@ -2692,13 +2709,23 @@ static int virtnet_receive_packets(struct
> virtnet_info *vi,
> > >       int packets = 0;
> > >       void *buf;
> > >
> > > -     if (!vi->big_packets || vi->mergeable_rx_bufs) {
> > > +     if (vi->mergeable_rx_bufs) {
> > >               void *ctx;
> > >               while (packets < budget &&
> > >                      (buf = virtnet_rq_get_buf(rq, &len, &ctx))) {
> > >                       receive_buf(vi, rq, buf, len, ctx, xdp_xmit,
> stats);
> > >                       packets++;
> > >               }
> > > +     } else if (!vi->big_packets) {
> > > +             void *ctx;
> > > +             unsigned int xdp_headroom = virtnet_get_headroom(vi);
> > > +             unsigned int header_offset = VIRTNET_RX_PAD +
> xdp_headroom;
> > > +
> > > +             while (packets < budget &&
> > > +                    (buf = virtnet_rq_get_buf_small(rq, &len, &ctx,
> header_offset))) {
> > > +                     receive_buf(vi, rq, buf, len, ctx, xdp_xmit,
> stats);
> > > +                     packets++;
> > > +             }
> > >       } else {
> > >               while (packets < budget &&
> > >                      (buf = virtqueue_get_buf(rq->vq, &len)) != NULL) {
> > > --
> > > 2.20.1
> > >
>

Re: [External] Re: [PATCH v2] virtio_net: Fix mismatched buf address when unmapping for small packets

[Wenbo Li]

Thank you. I'll fix these in v3.

On 9/4/24 15:30, Xuan Zhuo wrote:
> On Wed, 4 Sep 2024 15:21:28 +0800, =?utf-8?b?5paH5Y2a5p2O?= <liwenbo.martin@bytedance.com> wrote:
>> When SWIOTLB is enabled, a DMA map will allocate a bounce buffer for real
>> DMA operations,
>> and when unmapping, SWIOTLB copies the content in the bounce buffer to the
>> driver-allocated
>> buffer (the `buf` variable). Such copy only synchronizes data in the buffer
>> range, not the whole page.
>> So we should give the correct offset for DMA unmapping.
> I see.
>
> But I think we should pass the "correct" buf to virtio core as the "data" by
> virtqueue_add_inbuf_ctx().
>
> In the merge mode, we pass the pointer that points to the virtnet header.
> In the small mode, we pass the pointer that points to the virtnet header - offset.
>
> But this is not the only problem, we try to get the virtnet header by the buf
> inside receive_buf(before receive_small).
>
> 	flags = ((struct virtio_net_common_hdr *)buf)->hdr.flags;
>
> So I think it is time to unify the buf that passed to the virtio core into a
> pointer pointed to the virtnet header.
>
> Thanks.
>
>
>> Thanks.
>>
>> On Wed, Sep 4, 2024 at 2:46 PM Xuan Zhuo <xuanzhuo@linux.alibaba.com> wrote:
>>> On Wed,  4 Sep 2024 14:10:09 +0800, Wenbo Li <liwenbo.martin@bytedance.com>
>> wrote:
>>>> Currently, the virtio-net driver will perform a pre-dma-mapping for
>>>> small or mergeable RX buffer. But for small packets, a mismatched
>> address
>>>> without VIRTNET_RX_PAD and xdp_headroom is used for unmapping.
>>> Will used virt_to_head_page(), so could you say more about it?
>>>
>>>          struct page *page = virt_to_head_page(buf);
>>>
>>> Thanks.
>>>
>>>> That will result in unsynchronized buffers when SWIOTLB is enabled, for
>>>> example, when running as a TDX guest.
>>>>
>>>> This patch handles small and mergeable packets separately and fixes
>>>> the mismatched buffer address.
>>>>
>>>> Changes from v1: Use ctx to get xdp_headroom.
>>>>
>>>> Fixes: 295525e29a5b ("virtio_net: merge dma operations when filling
>> mergeable buffers")
>>>> Signed-off-by: Wenbo Li <liwenbo.martin@bytedance.com>
>>>> Signed-off-by: Jiahui Cen <cenjiahui@bytedance.com>
>>>> Signed-off-by: Ying Fang <fangying.tommy@bytedance.com>
>>>> ---
>>>>   drivers/net/virtio_net.c | 29 ++++++++++++++++++++++++++++-
>>>>   1 file changed, 28 insertions(+), 1 deletion(-)
>>>>
>>>> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
>>>> index c6af18948..cbc3c0ae4 100644
>>>> --- a/drivers/net/virtio_net.c
>>>> +++ b/drivers/net/virtio_net.c
>>>> @@ -891,6 +891,23 @@ static void *virtnet_rq_get_buf(struct
>> receive_queue *rq, u32 *len, void **ctx)
>>>>        return buf;
>>>>   }
>>>>
>>>> +static void *virtnet_rq_get_buf_small(struct receive_queue *rq,
>>>> +                                   u32 *len,
>>>> +                                   void **ctx,
>>>> +                                   unsigned int header_offset)
>>>> +{
>>>> +     void *buf;
>>>> +     unsigned int xdp_headroom;
>>>> +
>>>> +     buf = virtqueue_get_buf_ctx(rq->vq, len, ctx);
>>>> +     if (buf) {
>>>> +             xdp_headroom = (unsigned long)*ctx;
>>>> +             virtnet_rq_unmap(rq, buf + VIRTNET_RX_PAD + xdp_headroom,
>> *len);
>>>> +     }
>>>> +
>>>> +     return buf;
>>>> +}
>>>> +
>>>>   static void virtnet_rq_init_one_sg(struct receive_queue *rq, void
>> *buf, u32 len)
>>>>   {
>>>>        struct virtnet_rq_dma *dma;
>>>> @@ -2692,13 +2709,23 @@ static int virtnet_receive_packets(struct
>> virtnet_info *vi,
>>>>        int packets = 0;
>>>>        void *buf;
>>>>
>>>> -     if (!vi->big_packets || vi->mergeable_rx_bufs) {
>>>> +     if (vi->mergeable_rx_bufs) {
>>>>                void *ctx;
>>>>                while (packets < budget &&
>>>>                       (buf = virtnet_rq_get_buf(rq, &len, &ctx))) {
>>>>                        receive_buf(vi, rq, buf, len, ctx, xdp_xmit,
>> stats);
>>>>                        packets++;
>>>>                }
>>>> +     } else if (!vi->big_packets) {
>>>> +             void *ctx;
>>>> +             unsigned int xdp_headroom = virtnet_get_headroom(vi);
>>>> +             unsigned int header_offset = VIRTNET_RX_PAD +
>> xdp_headroom;
>>>> +
>>>> +             while (packets < budget &&
>>>> +                    (buf = virtnet_rq_get_buf_small(rq, &len, &ctx,
>> header_offset))) {
>>>> +                     receive_buf(vi, rq, buf, len, ctx, xdp_xmit,
>> stats);
>>>> +                     packets++;
>>>> +             }
>>>>        } else {
>>>>                while (packets < budget &&
>>>>                       (buf = virtqueue_get_buf(rq->vq, &len)) != NULL) {
>>>> --
>>>> 2.20.1
>>>>

Re: [External] Re: [PATCH v2] virtio_net: Fix mismatched buf address when unmapping for small packets

[Michael S. Tsirkin]

On Wed, Sep 04, 2024 at 03:30:02PM +0800, Xuan Zhuo wrote:
> On Wed, 4 Sep 2024 15:21:28 +0800, =?utf-8?b?5paH5Y2a5p2O?= <liwenbo.martin@bytedance.com> wrote:
> > When SWIOTLB is enabled, a DMA map will allocate a bounce buffer for real
> > DMA operations,
> > and when unmapping, SWIOTLB copies the content in the bounce buffer to the
> > driver-allocated
> > buffer (the `buf` variable). Such copy only synchronizes data in the buffer
> > range, not the whole page.
> > So we should give the correct offset for DMA unmapping.
> 
> I see.
> 
> But I think we should pass the "correct" buf to virtio core as the "data" by
> virtqueue_add_inbuf_ctx().
> 
> In the merge mode, we pass the pointer that points to the virtnet header.
> In the small mode, we pass the pointer that points to the virtnet header - offset.
> 
> But this is not the only problem, we try to get the virtnet header by the buf
> inside receive_buf(before receive_small).
> 
> 	flags = ((struct virtio_net_common_hdr *)buf)->hdr.flags;
> 
> So I think it is time to unify the buf that passed to the virtio core into a
> pointer pointed to the virtnet header.
> 
> Thanks.

Hard to say without seeing what is proposed, but I think
data pointer is opaque to virtio, it does not have to
point to anything specific - just !NULL.


> 
> >
> > Thanks.
> >
> > On Wed, Sep 4, 2024 at 2:46 PM Xuan Zhuo <xuanzhuo@linux.alibaba.com> wrote:
> > >
> > > On Wed,  4 Sep 2024 14:10:09 +0800, Wenbo Li <liwenbo.martin@bytedance.com>
> > wrote:
> > > > Currently, the virtio-net driver will perform a pre-dma-mapping for
> > > > small or mergeable RX buffer. But for small packets, a mismatched
> > address
> > > > without VIRTNET_RX_PAD and xdp_headroom is used for unmapping.
> > >
> > > Will used virt_to_head_page(), so could you say more about it?
> > >
> > >         struct page *page = virt_to_head_page(buf);
> > >
> > > Thanks.
> > >
> > > >
> > > > That will result in unsynchronized buffers when SWIOTLB is enabled, for
> > > > example, when running as a TDX guest.
> > > >
> > > > This patch handles small and mergeable packets separately and fixes
> > > > the mismatched buffer address.
> > > >
> > > > Changes from v1: Use ctx to get xdp_headroom.
> > > >
> > > > Fixes: 295525e29a5b ("virtio_net: merge dma operations when filling
> > mergeable buffers")
> > > > Signed-off-by: Wenbo Li <liwenbo.martin@bytedance.com>
> > > > Signed-off-by: Jiahui Cen <cenjiahui@bytedance.com>
> > > > Signed-off-by: Ying Fang <fangying.tommy@bytedance.com>
> > > > ---
> > > >  drivers/net/virtio_net.c | 29 ++++++++++++++++++++++++++++-
> > > >  1 file changed, 28 insertions(+), 1 deletion(-)
> > > >
> > > > diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> > > > index c6af18948..cbc3c0ae4 100644
> > > > --- a/drivers/net/virtio_net.c
> > > > +++ b/drivers/net/virtio_net.c
> > > > @@ -891,6 +891,23 @@ static void *virtnet_rq_get_buf(struct
> > receive_queue *rq, u32 *len, void **ctx)
> > > >       return buf;
> > > >  }
> > > >
> > > > +static void *virtnet_rq_get_buf_small(struct receive_queue *rq,
> > > > +                                   u32 *len,
> > > > +                                   void **ctx,
> > > > +                                   unsigned int header_offset)
> > > > +{
> > > > +     void *buf;
> > > > +     unsigned int xdp_headroom;
> > > > +
> > > > +     buf = virtqueue_get_buf_ctx(rq->vq, len, ctx);
> > > > +     if (buf) {
> > > > +             xdp_headroom = (unsigned long)*ctx;
> > > > +             virtnet_rq_unmap(rq, buf + VIRTNET_RX_PAD + xdp_headroom,
> > *len);
> > > > +     }
> > > > +
> > > > +     return buf;
> > > > +}
> > > > +
> > > >  static void virtnet_rq_init_one_sg(struct receive_queue *rq, void
> > *buf, u32 len)
> > > >  {
> > > >       struct virtnet_rq_dma *dma;
> > > > @@ -2692,13 +2709,23 @@ static int virtnet_receive_packets(struct
> > virtnet_info *vi,
> > > >       int packets = 0;
> > > >       void *buf;
> > > >
> > > > -     if (!vi->big_packets || vi->mergeable_rx_bufs) {
> > > > +     if (vi->mergeable_rx_bufs) {
> > > >               void *ctx;
> > > >               while (packets < budget &&
> > > >                      (buf = virtnet_rq_get_buf(rq, &len, &ctx))) {
> > > >                       receive_buf(vi, rq, buf, len, ctx, xdp_xmit,
> > stats);
> > > >                       packets++;
> > > >               }
> > > > +     } else if (!vi->big_packets) {
> > > > +             void *ctx;
> > > > +             unsigned int xdp_headroom = virtnet_get_headroom(vi);
> > > > +             unsigned int header_offset = VIRTNET_RX_PAD +
> > xdp_headroom;
> > > > +
> > > > +             while (packets < budget &&
> > > > +                    (buf = virtnet_rq_get_buf_small(rq, &len, &ctx,
> > header_offset))) {
> > > > +                     receive_buf(vi, rq, buf, len, ctx, xdp_xmit,
> > stats);
> > > > +                     packets++;
> > > > +             }
> > > >       } else {
> > > >               while (packets < budget &&
> > > >                      (buf = virtqueue_get_buf(rq->vq, &len)) != NULL) {
> > > > --
> > > > 2.20.1
> > > >
> >