diff options
| author | Michael S. Tsirkin <mst@redhat.com> | 2025-10-31 14:05:51 +0800 |
|---|---|---|
| committer | Jakub Kicinski <kuba@kernel.org> | 2025-11-04 17:14:07 -0800 |
| commit | c3838262b824c71c145cd3668722e99a69bc9cd9 (patch) | |
| tree | 5ac686699c9fe70fd2eb7d2467f86f02376b34e4 /drivers/net/virtio_net.c | |
| parent | e120f46768d98151ece8756ebd688b0e43dc8b29 (diff) | |
virtio_net: fix alignment for virtio_net_hdr_v1_hash
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>
Diffstat (limited to 'drivers/net/virtio_net.c')
| -rw-r--r-- | drivers/net/virtio_net.c | 15 |
1 files changed, 13 insertions, 2 deletions
diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c index 8e8a179aaa49..e6e650bc3bc3 100644 --- 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 struct virtio_net_hdr_v1_hash *hdr_hash, 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 *sq, struct sk_buff *skb, bool orphan) 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; @@ -6750,7 +6761,7 @@ static int virtnet_xdp_rx_hash(const struct xdp_md *_ctx, u32 *hash, 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; } |