From nobody Fri Dec 19 14:44:32 2025 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 5BF7427C863 for ; Tue, 20 May 2025 11:05:39 +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=1747739140; cv=none; b=lfZQo7YL1UpeKu+Mv+zcojfusNwgfKe3xe0qVCGth1jYhNO/u9qIX045bH7PGVrrhVrajbdYxFUdESCQxRJsyhwylCxF7Q1HDOYfcFENPzhZaGKSLxJrBQ2xX03038vLchFZiN6rsuqVSGydUSrk4g2sQH5uqdmTVl3Td2sw8gI= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1747739140; c=relaxed/simple; bh=b+YrCJ42KjHUkvwgT4xR/mxKsHO8cOHl9FN4Vq7fOL4=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=Z4pbVjkfttYI/7LnDwpo4CQA9DoDN/Xu4HLBCRPIakzYpu74M2yX9yfIvtYQ77exgvMvJgVWCxWWlYxaOX74CLUWgl2aiilw/Jw6vOVjaPimryuvC84yfMSjpLQvei4h0/18NMArMx7diQeyeHkhzit2hlUvO+GPZDrCvImNX9g= 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=KsefpQsp; 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="KsefpQsp" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1747739138; 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: in-reply-to:in-reply-to:references:references; bh=j3L6s3nZuJ4uDKFUqy+XqgUhFnSv9Fk5O3ApL5qopTw=; b=KsefpQsp0V25jbLE2/os+ZwpM2Okn5q3/qMU47EOPGIhkSSQlRyTmTkivm2j1soxWx+igv UQVZimwZcp3AlDpYv6s1HoQKSK4kHQAzerb8uEAGmr9lW+sz0NOgE2dVKXm7sIGwdLUnWv Q1Qz/owv7QzYO7vycXYGdVFSdqX5ANo= Received: from mx-prod-mc-06.mail-002.prod.us-west-2.aws.redhat.com (ec2-35-165-154-97.us-west-2.compute.amazonaws.com [35.165.154.97]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-82-fTA5-6DCO7aER2-un1MXKQ-1; Tue, 20 May 2025 07:05:36 -0400 X-MC-Unique: fTA5-6DCO7aER2-un1MXKQ-1 X-Mimecast-MFC-AGG-ID: fTA5-6DCO7aER2-un1MXKQ_1747739135 Received: from mx-prod-int-04.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-04.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.40]) (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-06.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 9369F180034E; Tue, 20 May 2025 11:05:35 +0000 (UTC) Received: from lenovo-t14s.redhat.com (unknown [10.44.33.64]) by mx-prod-int-04.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTP id B003E19560A3; Tue, 20 May 2025 11:05:33 +0000 (UTC) From: Laurent Vivier To: linux-kernel@vger.kernel.org Cc: Jason Wang , "Michael S. Tsirkin" , netdev@vger.kernel.org, Xuan Zhuo Subject: [PATCH 2/2] virtio_net: Enforce minimum TX ring size for reliability Date: Tue, 20 May 2025 13:05:26 +0200 Message-ID: <20250520110526.635507-3-lvivier@redhat.com> In-Reply-To: <20250520110526.635507-1-lvivier@redhat.com> References: <20250520110526.635507-1-lvivier@redhat.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-Scanned-By: MIMEDefang 3.0 on 10.30.177.40 Content-Type: text/plain; charset="utf-8" The `tx_may_stop()` logic stops TX queues if free descriptors (`sq->vq->num_free`) fall below the threshold of (2 + `MAX_SKB_FRAGS`). If the total ring size (`ring_num`) is not strictly greater than this value, queues can become persistently stopped or stop after minimal use, severely degrading performance. A single sk_buff transmission typically requires descriptors for: - The virtio_net_hdr (1 descriptor) - The sk_buff's linear data (head) (1 descriptor) - Paged fragments (up to MAX_SKB_FRAGS descriptors) This patch enforces that the TX ring size ('ring_num') must be strictly greater than (2 + MAX_SKB_FRAGS). This ensures that the ring is always large enough to hold at least one maximally-fragmented packet plus at least one additional slot. Reported-by: Lei Yang Signed-off-by: Laurent Vivier Acked-by: Jason Wang --- drivers/net/virtio_net.c | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c index e53ba600605a..866961f368a2 100644 --- a/drivers/net/virtio_net.c +++ b/drivers/net/virtio_net.c @@ -3481,6 +3481,12 @@ static int virtnet_tx_resize(struct virtnet_info *vi= , struct send_queue *sq, { int qindex, err; =20 + if (ring_num <=3D 2+MAX_SKB_FRAGS) { + netdev_err(vi->dev, "tx size (%d) cannot be smaller than %d\n", + ring_num, 2+MAX_SKB_FRAGS); + return -EINVAL; + } + qindex =3D sq - vi->sq; =20 virtnet_tx_pause(vi, sq); --=20 2.49.0