From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) (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 53A42345752 for ; Wed, 8 Apr 2026 14:35:00 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=170.10.129.124 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1775658901; cv=none; b=AwYsxijxK+PJS1RMQZHZLTZOKvXwbIjE9k87Ch90pe8x8Hmh2Qcz1U3JOr9xRGYDTMCDI9s5rXmGNve1z4B7FtFXpeL0ci57ftLmSesA67NB7OPE34HoUtz0kBxlIYFuy+HZ5dA1smAXilfqxsrWVagxBuJPJwNyAZU4lgbpNyE= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1775658901; c=relaxed/simple; bh=N7XK2sc9Y3RBBMpaH0o/Ed414b2BWZC+QsSoE0jg1II=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=RIomxilJlJDLUIvQk+Q52B1M1eT2v+trsIDBjSL8io+HCv+s/5500okb+oCi33quKP/X8gcxxaTQYwrOYy0KIswqn6DfG1eLtcijPoyfTWcswxfxG0MFFT4zNfQIHfJVOX972dhZO04m967wlbURowZARy/HjQ637weMHkUSimY= 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=aAnB3L2F; dkim=pass (2048-bit key) header.d=redhat.com header.i=@redhat.com header.b=pDquGTlJ; arc=none smtp.client-ip=170.10.129.124 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="aAnB3L2F"; dkim=pass (2048-bit key) header.d=redhat.com header.i=@redhat.com header.b="pDquGTlJ" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1775658899; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=x4/BN8y0SPi4BZrletYbddWuxFfzk7dPv2eFPKQlKnM=; b=aAnB3L2FAgGlv9YKGgaoQkBWn0ygb2aK1miVCPDsXxzQS6s0XyVkOO/lbxOuksfif4wNBl jxok3dPkOL2LRahBgpTAUJRr9v52OOhei7sUVEgyX7rcexXd9GQiw8Ekpx7plJWjf3peoj bccNuTU24sQQWJnp+uc0TpLhg0wI6ug= Received: from mail-wm1-f69.google.com (mail-wm1-f69.google.com [209.85.128.69]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-157-S4sVfwyRNX-QoWiLmHuH6w-1; Wed, 08 Apr 2026 10:34:56 -0400 X-MC-Unique: S4sVfwyRNX-QoWiLmHuH6w-1 X-Mimecast-MFC-AGG-ID: S4sVfwyRNX-QoWiLmHuH6w_1775658896 Received: by mail-wm1-f69.google.com with SMTP id 5b1f17b1804b1-4888b17ffa6so49320145e9.3 for ; Wed, 08 Apr 2026 07:34:56 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=google; t=1775658896; x=1776263696; darn=vger.kernel.org; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:from:to:cc:subject:date:message-id:reply-to; bh=x4/BN8y0SPi4BZrletYbddWuxFfzk7dPv2eFPKQlKnM=; b=pDquGTlJnD+5uMAb036rGsMin89OhBQC0lcjyPXFVvhky3/wxE1eswixNwK8Dz5RUo 4Hq2sKLmWyuZ9MgeyjvW3RTMdJAcOrxhIK94RPsrbQ8rdmdzbK72hSCeEU2xWVZCbUQZ ACb//SuWKgv48zdizzGPJGAorghO4coSNAoukbmOu3Qs+bOFMgjrVeuM4BGFWns+S2uK s9r86H7sZzV1ziifU9m2zbGGP0aBvwX/ZGgw4G/SSSiOCy52CZ/UDhix8r3bQb4kTK85 2o7RIcdcxyROlBQf3IYCwNRNgOLpBKyTa9/zeRkiZOg12ARWGpXhS+uKz2pvE5o/BVln QCQg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1775658896; x=1776263696; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:x-gm-gg:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=x4/BN8y0SPi4BZrletYbddWuxFfzk7dPv2eFPKQlKnM=; b=b89+VQk/FlE34MJqedlWivtw+VtE51IOmZRoAR5BfETTrHtiaiBqYWHeda/7BEXQfV p4QO1pScHUoGHhvikq9t5AGrVXsogHOO1cPmVFSKBfaM0lvmFtRtFC5GYPoxNU/f8DNx dRZJ82D/zAoLdi4eeDQA7JWggmMiyJm8DaSldZJ6iilGg55lIL7jfMnVeqkRWznC3/wx ZU+5vW1/MyyePVeaJpVn8jP4H7psG0HUYi9VZCmGvaTPPZ4lI1jarX8cIAsyI7F5TiUJ bcgWZu8FMCzll1qypNwHB2MWtDTGoLteY2czldDpb/p5h0DpU8V78cN+rs6dA8kxM9mI 9UUQ== X-Forwarded-Encrypted: i=1; AJvYcCVHjIm+4qo/Lvo+hi68onCZ7QsX4nQzXVjPfIcwhA9H+yhIkQfGqE+bqwGQpZ7uyPkhX8QiaTA=@vger.kernel.org X-Gm-Message-State: AOJu0YwhZJuhqu72AAFsTNvPzRIyErsggW7h8jzz0UeUrZFE4XyRGAfa MoH4Ysma7MTozEiDGzUe4+vZAfOoowGjdwY5gma1ooEvgxdAC2D3Z1OP3RLeslasIljaeXtcHIO iYA3NBPox1LlxKxFBF1yPe2ryeB1+B+zVV2cOAc9K++ZXMqSUjIBf4PAjzw== X-Gm-Gg: AeBDietFwE/z8IPoeL5pPb6LQLbbUN4z3QYvlvcPk2IFYaiDmO9GKmGN3zwMJkQjYX6 YM7euGpPgZ9AW0u8RESlzGmn2leK9YAJfq3zx4UcgSEAAGzG6zynzKTjiwxTxQreWQmm/QNQdml HIQv4T1zmOZDAgL+OVBmaQOKDxdznD4O7xtS6OO8XL1ZvHIu/+xKcWOVoZCnmLb5XToxgMlIn1x 4Rd1+iqdCtHYB1DBSwiUJcN84YdZOS9ree7X8M9MpRJnS3NPXyizDidKwweG7g7FdWx5ZU56dQE Dd5cucazLWv8Qb3SuIgercJY4ehupI9dDo+s7b+FYRsE1jQ2ed+YHSZ2cNo35u9NdJCZtV2SOZw duBw5K14iVxAKYcxsb+D0Atsx7p6UK5ztBtZac/TUmKE= X-Received: by 2002:a05:600c:c11b:b0:488:be58:bb5b with SMTP id 5b1f17b1804b1-488be58c8fbmr73118295e9.24.1775658895502; Wed, 08 Apr 2026 07:34:55 -0700 (PDT) X-Received: by 2002:a05:600c:c11b:b0:488:be58:bb5b with SMTP id 5b1f17b1804b1-488be58c8fbmr73118015e9.24.1775658894950; Wed, 08 Apr 2026 07:34:54 -0700 (PDT) Received: from redhat.com (IGLD-80-230-25-21.inter.net.il. [80.230.25.21]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-4888a7165aasm651511625e9.14.2026.04.08.07.34.53 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 08 Apr 2026 07:34:54 -0700 (PDT) Date: Wed, 8 Apr 2026 10:34:52 -0400 From: "Michael S. Tsirkin" To: Sasha Levin Cc: Srujana Challa , "stable@vger.kernel.org" , Jakub Kicinski Subject: Re: [EXTERNAL] [PATCH 6.12.y] virtio_net: clamp rss_max_key_size to NETDEV_RSS_KEY_LEN Message-ID: <20260408103355-mutt-send-email-mst@kernel.org> References: <2026040855-hatless-marbled-c4ed@gregkh> <20260408131906.1087303-1-sashal@kernel.org> Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: On Wed, Apr 08, 2026 at 10:14:13AM -0400, Sasha Levin wrote: > On Wed, Apr 08, 2026 at 01:49:48PM +0000, Srujana Challa wrote: > > > From: Srujana Challa > > > > > > [ Upstream commit b4e5f04c58a29c499faa85d12952ca9a4faf1cb9 ] > > > > > > rss_max_key_size in the virtio spec is the maximum key size supported by the > > > device, not a mandatory size the driver must use. Also the value 40 is a spec > > > minimum, not a spec maximum. > > > > > > The current code rejects RSS and can fail probe when the device reports a > > > larger rss_max_key_size than the driver buffer limit. Instead, clamp the > > > effective key length to min(device rss_max_key_size, NETDEV_RSS_KEY_LEN) > > > and keep RSS enabled. > > > > > > This keeps probe working on devices that advertise larger maximum key sizes > > > while respecting the netdev RSS key buffer size limit. > > > > > > Fixes: 3f7d9c1964fc ("virtio_net: Add hash_key_length check") > > > Cc: stable@vger.kernel.org > > > Signed-off-by: Srujana Challa > > > Acked-by: Michael S. Tsirkin > > > Link: https://urldefense.proofpoint.com/v2/url?u=https- > > > 3A__patch.msgid.link_20260326142344.1171317-2D1-2Dschalla- > > > 40marvell.com&d=DwIDAg&c=nKjWec2b6R0mOyPaz7xtfQ&r=Fj4OoD5hcKFp > > > ANhTWdwQzjT1Jpf7veC5263T47JVpnc&m=0XuKVXgk9_1LUIZHeqL0znGhAh > > > x5KvAOLvrCl-orVeQSt__4o6Djr-79rwCl6KNp&s=cfQpAcZTTE7nTYku- > > > MVkfip0xUJoBBw4ikqm9iEdgcc&e= > > > Signed-off-by: Jakub Kicinski [ changed clamp target from > > > NETDEV_RSS_KEY_LEN to VIRTIO_NET_RSS_MAX_KEY_SIZE ] > > > Signed-off-by: Sasha Levin > > > --- > > > drivers/net/virtio_net.c | 16 ++++++++-------- > > > 1 file changed, 8 insertions(+), 8 deletions(-) > > > > > > diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c index > > > 5c83983f0eb3f..5a31ccdae2e22 100644 > > > --- a/drivers/net/virtio_net.c > > > +++ b/drivers/net/virtio_net.c > > > @@ -6502,6 +6502,7 @@ static int virtnet_probe(struct virtio_device *vdev) > > > struct virtnet_info *vi; > > > u16 max_queue_pairs; > > > int mtu = 0; > > > + u16 key_sz; > > > > > > /* Find if host supports multiqueue/rss virtio_net device */ > > > max_queue_pairs = 1; > > > @@ -6624,14 +6625,13 @@ static int virtnet_probe(struct virtio_device > > > *vdev) > > > goto free; > > > > > > if (vi->has_rss || vi->has_rss_hash_report) { > > > - vi->rss_key_size = > > > - virtio_cread8(vdev, offsetof(struct virtio_net_config, > > > rss_max_key_size)); > > > - if (vi->rss_key_size > VIRTIO_NET_RSS_MAX_KEY_SIZE) { > > > - dev_err(&vdev->dev, "rss_max_key_size=%u exceeds > > > the limit %u.\n", > > > - vi->rss_key_size, > > > VIRTIO_NET_RSS_MAX_KEY_SIZE); > > > - err = -EINVAL; > > > - goto free; > > > - } > > > + key_sz = virtio_cread8(vdev, offsetof(struct virtio_net_config, > > > +rss_max_key_size)); > > > + > > > + vi->rss_key_size = min_t(u16, key_sz, > > > VIRTIO_NET_RSS_MAX_KEY_SIZE); > > > + if (key_sz > vi->rss_key_size) > > > + dev_warn(&vdev->dev, > > > + "rss_max_key_size=%u exceeds driver limit > > > %u, clamping\n", > > > + key_sz, vi->rss_key_size); > > > > > > vi->rss_hash_types_supported = > > > virtio_cread32(vdev, offsetof(struct virtio_net_config, > > > supported_hash_types)); > > > -- > > > 2.53.0 > > > > We used `NETDEV_RSS_KEY_LEN` intentionally for clamping. > > `rss_max_key_size` is the maximum supported by the device, > > while `40` is a spec minimum, not a maximum. > > Clamping to `VIRTIO_NET_RSS_MAX_KEY_SIZE` would unnecessarily > > limit valid devices(for example devices advertising 48/52 bytes) and > > could reintroduce the original issue. > > > > Could you please share the reason for changing the clamp target > > from `NETDEV_RSS_KEY_LEN` to `VIRTIO_NET_RSS_MAX_KEY_SIZE`? > > Hi Srujana, > > In the upstream commit, the key buffer was also enlarged from 40 to 52 bytes as > part of the `TRAILING_OVERLAP` / `rss_trailer` refactoring: > > - u8 rss_hash_key_data[VIRTIO_NET_RSS_MAX_KEY_SIZE]; > + u8 rss_hash_key_data[NETDEV_RSS_KEY_LEN]; > > That refactoring isn't present in 6.12, so the key buffer is still `u8 > key[VIRTIO_NET_RSS_MAX_KEY_SIZE]` (40 bytes). Clamping to `NETDEV_RSS_KEY_LEN` > (52) here would allow writing up to 52 bytes into a 40-byte buffer, so the > clamp target had to match the actual buffer size in this tree. > > -- > Thanks, > Sasha problem is, the commit log now says one thing and the patch does a completely different, and in fact opposite, thing. Why not pick that dependency then? -- MST