From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 2B37E2E54DE for ; Fri, 31 Oct 2025 06:06:13 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=170.10.133.124 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1761890777; cv=none; b=i7hskyoNAJnx6B2WWO+JOa9Ia6PaeUViOLXmO66NBqcMBtX5+TmxWhBU4UjWSSG7euPLA+m+w9mFERfvpDieWBreuSsFao00lFM5RXpZPcxJvJKr7pd92S7qOxClhRYf3wcRYpJr5Kqcjagg6QnaM/o4P0Z4IGfwV2kL6dKczLQ= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1761890777; c=relaxed/simple; bh=uzKsr8p0ZgM+SLgICEjgau4Cc9/3BVPso+PqdA0y7L8=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version; b=SdVv3oDUymPKAYpwh6Bbm0NQQM6/+TZfMeVvWvU2LBuRaz35sXSmdhxG/IRR9CV9c+EuOl1CBZsS8qTEnOclHCq5R1WV9BsxgL8KNOkeyAArrKeIWJSQo4zTGlXdiJE7iR0uu8Bx2KhvPDnLr9eBEqio+h7iH9AVD7UeOwGXsc0= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=redhat.com; spf=pass smtp.mailfrom=redhat.com; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b=FoAGExTF; arc=none smtp.client-ip=170.10.133.124 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=redhat.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=redhat.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="FoAGExTF" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1761890773; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding; bh=+bCrk/NYYmYlKBsMjf6Y0gKt7P2+73Hm3s9fxJ/Q+sk=; b=FoAGExTF79kTZ/cca5BoXsCs3OUqZD6LQQnhZL1T2yKWxhb+mboPu6R/VlG00+R4RSfDii unBC9PZDUMZ4Tlz0PAfyq+zSPeOc9nAi3X4pM58m4M9Ol/wz9p/jRkbXcCTgeCXVGYnXiC XS49UR2hEy2dBDRI3tpadUsnVzJBd8o= Received: from mx-prod-mc-01.mail-002.prod.us-west-2.aws.redhat.com (ec2-54-186-198-63.us-west-2.compute.amazonaws.com [54.186.198.63]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-618-7ClablYyO1OVe2uC7hp5hQ-1; Fri, 31 Oct 2025 02:06:09 -0400 X-MC-Unique: 7ClablYyO1OVe2uC7hp5hQ-1 X-Mimecast-MFC-AGG-ID: 7ClablYyO1OVe2uC7hp5hQ_1761890768 Received: from mx-prod-int-05.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-05.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.17]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mx-prod-mc-01.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 79D581953958; Fri, 31 Oct 2025 06:06:07 +0000 (UTC) Received: from localhost.localdomain (unknown [10.72.120.6]) by mx-prod-int-05.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTP id 96EE21955BE3; Fri, 31 Oct 2025 06:05:55 +0000 (UTC) From: Jason Wang To: mst@redhat.com, jasowang@redhat.com, xuanzhuo@linux.alibaba.com, eperezma@redhat.com, andrew+netdev@lunn.ch, davem@davemloft.net, edumazet@google.com, kuba@kernel.org, pabeni@redhat.com Cc: virtualization@lists.linux.dev, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org Subject: [PATCH net V2] virtio_net: fix alignment for virtio_net_hdr_v1_hash Date: Fri, 31 Oct 2025 14:05:51 +0800 Message-ID: <20251031060551.126-1-jasowang@redhat.com> Precedence: bulk X-Mailing-List: virtualization@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Scanned-By: MIMEDefang 3.0 on 10.30.177.17 From: "Michael S. Tsirkin" 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 Signed-off-by: Jason Wang --- Changes since V1: - Fix build issues of virtio_net_hdr_tnl_from_skb() --- 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(-) 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 @@ static struct sk_buff *receive_mergeable(struct net_device *dev, 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; } diff --git a/include/linux/virtio_net.h b/include/linux/virtio_net.h index 4d1780848d0e..b673c31569f3 100644 --- a/include/linux/virtio_net.h +++ b/include/linux/virtio_net.h @@ -401,7 +401,8 @@ virtio_net_hdr_tnl_from_skb(const struct sk_buff *skb, 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; diff --git a/include/uapi/linux/virtio_net.h b/include/uapi/linux/virtio_net.h index 8bf27ab8bcb4..1db45b01532b 100644 --- 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 -- 2.31.1