diff mbox series

[net-next,v5,02/10] virtio-net: fix calculation of MTU for single-buffer xdp

Message ID 20230114082229.62143-3-hengqi@linux.alibaba.com (mailing list archive)
State Accepted
Commit e814b958ad8857d6f7354d3a189776eb604d86dd
Delegated to: Netdev Maintainers
Headers show
Series virtio-net: support multi buffer xdp | expand

Checks

Context Check Description
netdev/tree_selection success Clearly marked for net-next
netdev/fixes_present success Fixes tag not required for -next series
netdev/subject_prefix success Link
netdev/cover_letter success Series has a cover letter
netdev/patch_count success Link
netdev/header_inline success No static functions without inline keyword in header files
netdev/build_32bit success Errors and warnings before: 0 this patch: 0
netdev/cc_maintainers warning 2 maintainers not CCed: virtualization@lists.linux-foundation.org hawk@kernel.org
netdev/build_clang success Errors and warnings before: 0 this patch: 0
netdev/module_param success Was 0 now: 0
netdev/verify_signedoff success Signed-off-by tag matches author and committer
netdev/check_selftest success No net selftest shell script
netdev/verify_fixes success No Fixes tag
netdev/build_allmodconfig_warn success Errors and warnings before: 0 this patch: 0
netdev/checkpatch success total: 0 errors, 0 warnings, 0 checks, 18 lines checked
netdev/kdoc success Errors and warnings before: 0 this patch: 0
netdev/source_inline success Was 0 now: 0

Commit Message

Heng Qi Jan. 14, 2023, 8:22 a.m. UTC 
When single-buffer xdp is loaded, the size of the buffer filled each time
is 'sz = (PAGE_SIZE - headroom - tailroom)', which is the maximum packet
length that the driver allows the device to pass in. Otherwise, the packet
with a length greater than sz will come in, so num_buf will be greater than
or equal to 2, and xdp_linearize_page() will be performed and the packet
will be dropped because the total length is greater than PAGE_SIZE. So the
maximum value of MTU for single-buffer xdp is 'max_sz = sz - ETH_HLEN'.

Signed-off-by: Heng Qi <hengqi@linux.alibaba.com>
Reviewed-by: Xuan Zhuo <xuanzhuo@linux.alibaba.com>
Acked-by: Jason Wang <jasowang@redhat.com>
---
In fact, this is a fix patch belonging to the net branch, which needs
to be backported to the stable branch.

 drivers/net/virtio_net.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)
diff mbox series

Patch

diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index 443aa7b8f0ad..1203e4176b66 100644
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c
@@ -3074,7 +3074,9 @@  static int virtnet_restore_guest_offloads(struct virtnet_info *vi)
 static int virtnet_xdp_set(struct net_device *dev, struct bpf_prog *prog,
 			   struct netlink_ext_ack *extack)
 {
-	unsigned long int max_sz = PAGE_SIZE - sizeof(struct padded_vnet_hdr);
+	unsigned int room = SKB_DATA_ALIGN(VIRTIO_XDP_HEADROOM +
+					   sizeof(struct skb_shared_info));
+	unsigned int max_sz = PAGE_SIZE - room - ETH_HLEN;
 	struct virtnet_info *vi = netdev_priv(dev);
 	struct bpf_prog *old_prog;
 	u16 xdp_qp = 0, curr_qp;
@@ -3097,7 +3099,7 @@  static int virtnet_xdp_set(struct net_device *dev, struct bpf_prog *prog,
 
 	if (dev->mtu > max_sz) {
 		NL_SET_ERR_MSG_MOD(extack, "MTU too large to enable XDP");
-		netdev_warn(dev, "XDP requires MTU less than %lu\n", max_sz);
+		netdev_warn(dev, "XDP requires MTU less than %u\n", max_sz);
 		return -EINVAL;
 	}