6.17-stable review patch. If anyone has any objections, please let me know.
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From: Michael S. Tsirkin mst@redhat.com
commit c3838262b824c71c145cd3668722e99a69bc9cd9 upstream.
Changing alignment of header would mean it's no longer safe to cast a 2 byte aligned pointer between formats. Use two 16 bit fields to make it 2 byte aligned as previously.
This fixes the performance regression since commit ("virtio_net: enable gso over UDP tunnel support.") as it uses virtio_net_hdr_v1_hash_tunnel which embeds virtio_net_hdr_v1_hash. Pktgen in guest + XDP_DROP on TAP + vhost_net shows the TX PPS is recovered from 2.4Mpps to 4.45Mpps.
Fixes: 56a06bd40fab ("virtio_net: enable gso over UDP tunnel support.") Cc: stable@vger.kernel.org Signed-off-by: Michael S. Tsirkin mst@redhat.com Signed-off-by: Jason Wang jasowang@redhat.com Tested-by: Lei Yang leiyang@redhat.com Link: https://patch.msgid.link/20251031060551.126-1-jasowang@redhat.com Signed-off-by: Jakub Kicinski kuba@kernel.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- drivers/net/virtio_net.c | 15 +++++++++++++-- include/linux/virtio_net.h | 3 ++- include/uapi/linux/virtio_net.h | 3 ++- 3 files changed, 17 insertions(+), 4 deletions(-)
--- a/drivers/net/virtio_net.c +++ b/drivers/net/virtio_net.c @@ -2539,6 +2539,13 @@ err_buf: return NULL; }
+static inline u32 +virtio_net_hash_value(const struct virtio_net_hdr_v1_hash *hdr_hash) +{ + return __le16_to_cpu(hdr_hash->hash_value_lo) | + (__le16_to_cpu(hdr_hash->hash_value_hi) << 16); +} + static void virtio_skb_set_hash(const struct virtio_net_hdr_v1_hash *hdr_hash, struct sk_buff *skb) { @@ -2565,7 +2572,7 @@ static void virtio_skb_set_hash(const st default: rss_hash_type = PKT_HASH_TYPE_NONE; } - skb_set_hash(skb, __le32_to_cpu(hdr_hash->hash_value), rss_hash_type); + skb_set_hash(skb, virtio_net_hash_value(hdr_hash), rss_hash_type); }
static void virtnet_receive_done(struct virtnet_info *vi, struct receive_queue *rq, @@ -3311,6 +3318,10 @@ static int xmit_skb(struct send_queue *s
pr_debug("%s: xmit %p %pM\n", vi->dev->name, skb, dest);
+ /* Make sure it's safe to cast between formats */ + BUILD_BUG_ON(__alignof__(*hdr) != __alignof__(hdr->hash_hdr)); + BUILD_BUG_ON(__alignof__(*hdr) != __alignof__(hdr->hash_hdr.hdr)); + can_push = vi->any_header_sg && !((unsigned long)skb->data & (__alignof__(*hdr) - 1)) && !skb_header_cloned(skb) && skb_headroom(skb) >= hdr_len; @@ -6759,7 +6770,7 @@ static int virtnet_xdp_rx_hash(const str hash_report = VIRTIO_NET_HASH_REPORT_NONE;
*rss_type = virtnet_xdp_rss_type[hash_report]; - *hash = __le32_to_cpu(hdr_hash->hash_value); + *hash = virtio_net_hash_value(hdr_hash); return 0; }
--- a/include/linux/virtio_net.h +++ b/include/linux/virtio_net.h @@ -401,7 +401,8 @@ virtio_net_hdr_tnl_from_skb(const struct if (!tnl_hdr_negotiated) return -EINVAL;
- vhdr->hash_hdr.hash_value = 0; + vhdr->hash_hdr.hash_value_lo = 0; + vhdr->hash_hdr.hash_value_hi = 0; vhdr->hash_hdr.hash_report = 0; vhdr->hash_hdr.padding = 0;
--- a/include/uapi/linux/virtio_net.h +++ b/include/uapi/linux/virtio_net.h @@ -193,7 +193,8 @@ struct virtio_net_hdr_v1 {
struct virtio_net_hdr_v1_hash { struct virtio_net_hdr_v1 hdr; - __le32 hash_value; + __le16 hash_value_lo; + __le16 hash_value_hi; #define VIRTIO_NET_HASH_REPORT_NONE 0 #define VIRTIO_NET_HASH_REPORT_IPv4 1 #define VIRTIO_NET_HASH_REPORT_TCPv4 2