| Message ID | 20241029084615.91049-2-xuanzhuo@linux.alibaba.com (mailing list archive) |
|---|---|
| State | Accepted |
| Commit | 6aacd1484468361d1d04badfe75f264fa5314864 |
| Delegated to: | Netdev Maintainers |
| Headers | show |
| Series | virtio_net: enable premapped mode by default | expand |
On Tue, Oct 29, 2024 at 4:47 PM Xuan Zhuo <xuanzhuo@linux.alibaba.com> wrote: > > When the frag just got a page, then may lead to regression on VM. > Specially if the sysctl net.core.high_order_alloc_disable value is 1, > then the frag always get a page when do refill. > > Which could see reliable crashes or scp failure (scp a file 100M in size > to VM). > > The issue is that the virtnet_rq_dma takes up 16 bytes at the beginning > of a new frag. When the frag size is larger than PAGE_SIZE, > everything is fine. However, if the frag is only one page and the > total size of the buffer and virtnet_rq_dma is larger than one page, an > overflow may occur. > > The commit f9dac92ba908 ("virtio_ring: enable premapped mode whatever > use_dma_api") introduced this problem. And we reverted some commits to > fix this in last linux version. Now we try to enable it and fix this > bug directly. > > Here, when the frag size is not enough, we reduce the buffer len to fix > this problem. > > Reported-by: "Si-Wei Liu" <si-wei.liu@oracle.com> > Tested-by: Darren Kenny <darren.kenny@oracle.com> > Signed-off-by: Xuan Zhuo <xuanzhuo@linux.alibaba.com> Acked-by: Jason Wang <jasowang@redhat.com> Thanks
On Tue, Oct 29, 2024 at 04:46:12PM +0800, Xuan Zhuo wrote: > When the frag just got a page, then may lead to regression on VM. > Specially if the sysctl net.core.high_order_alloc_disable value is 1, > then the frag always get a page when do refill. > > Which could see reliable crashes or scp failure (scp a file 100M in size > to VM). > > The issue is that the virtnet_rq_dma takes up 16 bytes at the beginning > of a new frag. When the frag size is larger than PAGE_SIZE, > everything is fine. However, if the frag is only one page and the > total size of the buffer and virtnet_rq_dma is larger than one page, an > overflow may occur. > > The commit f9dac92ba908 ("virtio_ring: enable premapped mode whatever > use_dma_api") introduced this problem. And we reverted some commits to > fix this in last linux version. Now we try to enable it and fix this > bug directly. > > Here, when the frag size is not enough, we reduce the buffer len to fix > this problem. > > Reported-by: "Si-Wei Liu" <si-wei.liu@oracle.com> > Tested-by: Darren Kenny <darren.kenny@oracle.com> > Signed-off-by: Xuan Zhuo <xuanzhuo@linux.alibaba.com> This one belongs in net I feel. However, patches 2 and on depend on it not to cause regressions. So I suggest merging it on both branches, git will figure out the conflict I think. > --- > drivers/net/virtio_net.c | 12 +++++++++--- > 1 file changed, 9 insertions(+), 3 deletions(-) > > diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c > index 792e9eadbfc3..d50c1940eb23 100644 > --- a/drivers/net/virtio_net.c > +++ b/drivers/net/virtio_net.c > @@ -926,9 +926,6 @@ static void *virtnet_rq_alloc(struct receive_queue *rq, u32 size, gfp_t gfp) > void *buf, *head; > dma_addr_t addr; > > - if (unlikely(!skb_page_frag_refill(size, alloc_frag, gfp))) > - return NULL; > - > head = page_address(alloc_frag->page); > > if (rq->do_dma) { > @@ -2423,6 +2420,9 @@ static int add_recvbuf_small(struct virtnet_info *vi, struct receive_queue *rq, > len = SKB_DATA_ALIGN(len) + > SKB_DATA_ALIGN(sizeof(struct skb_shared_info)); > > + if (unlikely(!skb_page_frag_refill(len, &rq->alloc_frag, gfp))) > + return -ENOMEM; > + > buf = virtnet_rq_alloc(rq, len, gfp); > if (unlikely(!buf)) > return -ENOMEM; > @@ -2525,6 +2525,12 @@ static int add_recvbuf_mergeable(struct virtnet_info *vi, > */ > len = get_mergeable_buf_len(rq, &rq->mrg_avg_pkt_len, room); > > + if (unlikely(!skb_page_frag_refill(len + room, alloc_frag, gfp))) > + return -ENOMEM; > + > + if (!alloc_frag->offset && len + room + sizeof(struct virtnet_rq_dma) > alloc_frag->size) > + len -= sizeof(struct virtnet_rq_dma); > + > buf = virtnet_rq_alloc(rq, len + room, gfp); > if (unlikely(!buf)) > return -ENOMEM; > -- > 2.32.0.3.g01195cf9f
diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c index 792e9eadbfc3..d50c1940eb23 100644 --- a/drivers/net/virtio_net.c +++ b/drivers/net/virtio_net.c @@ -926,9 +926,6 @@ static void *virtnet_rq_alloc(struct receive_queue *rq, u32 size, gfp_t gfp) void *buf, *head; dma_addr_t addr; - if (unlikely(!skb_page_frag_refill(size, alloc_frag, gfp))) - return NULL; - head = page_address(alloc_frag->page); if (rq->do_dma) { @@ -2423,6 +2420,9 @@ static int add_recvbuf_small(struct virtnet_info *vi, struct receive_queue *rq, len = SKB_DATA_ALIGN(len) + SKB_DATA_ALIGN(sizeof(struct skb_shared_info)); + if (unlikely(!skb_page_frag_refill(len, &rq->alloc_frag, gfp))) + return -ENOMEM; + buf = virtnet_rq_alloc(rq, len, gfp); if (unlikely(!buf)) return -ENOMEM; @@ -2525,6 +2525,12 @@ static int add_recvbuf_mergeable(struct virtnet_info *vi, */ len = get_mergeable_buf_len(rq, &rq->mrg_avg_pkt_len, room); + if (unlikely(!skb_page_frag_refill(len + room, alloc_frag, gfp))) + return -ENOMEM; + + if (!alloc_frag->offset && len + room + sizeof(struct virtnet_rq_dma) > alloc_frag->size) + len -= sizeof(struct virtnet_rq_dma); + buf = virtnet_rq_alloc(rq, len + room, gfp); if (unlikely(!buf)) return -ENOMEM;
When the frag just got a page, then may lead to regression on VM. Specially if the sysctl net.core.high_order_alloc_disable value is 1, then the frag always get a page when do refill. Which could see reliable crashes or scp failure (scp a file 100M in size to VM). The issue is that the virtnet_rq_dma takes up 16 bytes at the beginning of a new frag. When the frag size is larger than PAGE_SIZE, everything is fine. However, if the frag is only one page and the total size of the buffer and virtnet_rq_dma is larger than one page, an overflow may occur. The commit f9dac92ba908 ("virtio_ring: enable premapped mode whatever use_dma_api") introduced this problem. And we reverted some commits to fix this in last linux version. Now we try to enable it and fix this bug directly. Here, when the frag size is not enough, we reduce the buffer len to fix this problem. Reported-by: "Si-Wei Liu" <si-wei.liu@oracle.com> Tested-by: Darren Kenny <darren.kenny@oracle.com> Signed-off-by: Xuan Zhuo <xuanzhuo@linux.alibaba.com> --- drivers/net/virtio_net.c | 12 +++++++++--- 1 file changed, 9 insertions(+), 3 deletions(-)