From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-17.5 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,NICE_REPLY_A, SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 1E064C433DB for ; Mon, 22 Mar 2021 03:23:30 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id EAD2A61939 for ; Mon, 22 Mar 2021 03:23:29 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229866AbhCVDWy (ORCPT ); Sun, 21 Mar 2021 23:22:54 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]:50724 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229621AbhCVDWg (ORCPT ); Sun, 21 Mar 2021 23:22:36 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1616383356; 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: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=7CxCPTphkLxAAe7WrRHdqu9Vis3F0z32vdPzkrtEuSY=; b=ZCUVfpSav6elQAMpAGFmVj9kWjAuTkPjN1X2d6b59ouTM1YxWqy0jbAFif0ae8sL98vc0u QTfpH67V0APGckVBeo8bVRXTztpzX4wRd4aOz7vpwUQ41Kv1MMZhP299X2P9jbEiU4GdY9 LWeLDvUkii3e3ql2EnD8oMXBgcWE0Pg= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-250-iZsFkDiAOR6s_9WODNEMaw-1; Sun, 21 Mar 2021 23:22:32 -0400 X-MC-Unique: iZsFkDiAOR6s_9WODNEMaw-1 Received: from smtp.corp.redhat.com (int-mx06.intmail.prod.int.phx2.redhat.com [10.5.11.16]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 646D8180FCA8; Mon, 22 Mar 2021 03:22:30 +0000 (UTC) Received: from wangxiaodeMacBook-Air.local (ovpn-13-188.pek2.redhat.com [10.72.13.188]) by smtp.corp.redhat.com (Postfix) with ESMTP id 046675F9C9; Mon, 22 Mar 2021 03:22:16 +0000 (UTC) Subject: Re: [PATCH 1/3] virtio_ring: always warn when descriptor chain exceeds queue size To: Connor Kuehl , virtio-fs@redhat.com Cc: linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, virtualization@lists.linux-foundation.org, stefanha@redhat.com, vgoyal@redhat.com, miklos@szeredi.hu, mst@redhat.com References: <20210318135223.1342795-1-ckuehl@redhat.com> <20210318135223.1342795-2-ckuehl@redhat.com> From: Jason Wang Message-ID: Date: Mon, 22 Mar 2021 11:22:15 +0800 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.16; rv:78.0) Gecko/20100101 Thunderbird/78.8.1 MIME-Version: 1.0 In-Reply-To: <20210318135223.1342795-2-ckuehl@redhat.com> Content-Type: text/plain; charset=gbk; format=flowed Content-Transfer-Encoding: 8bit X-Scanned-By: MIMEDefang 2.79 on 10.5.11.16 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org ÔÚ 2021/3/18 ÏÂÎç9:52, Connor Kuehl дµÀ: > From section 2.6.5.3.1 (Driver Requirements: Indirect Descriptors) > of the virtio spec: > > "A driver MUST NOT create a descriptor chain longer than the Queue > Size of the device." > > This text suggests that the warning should trigger even if > indirect descriptors are in use. So I think at least the commit log needs some tweak. For split virtqueue. We had: 2.6.5.2 Driver Requirements: The Virtqueue Descriptor Table Drivers MUST NOT add a descriptor chain longer than 2^32 bytes in total; this implies that loops in the descriptor chain are forbidden! 2.6.5.3.1 Driver Requirements: Indirect Descriptors A driver MUST NOT create a descriptor chain longer than the Queue Size of the device. If I understand the spec correctly, the check is only needed for a single indirect descriptor table? For packed virtqueue. We had: 2.7.17 Driver Requirements: Scatter-Gather Support A driver MUST NOT create a descriptor list longer than allowed by the device. A driver MUST NOT create a descriptor list longer than the Queue Size. 2.7.19 Driver Requirements: Indirect Descriptors A driver MUST NOT create a descriptor chain longer than allowed by the device. So it looks to me the packed part is fine. Note that if I understand the spec correctly 2.7.17 implies 2.7.19. Thanks > > Reported-by: Stefan Hajnoczi > Signed-off-by: Connor Kuehl > --- > drivers/virtio/virtio_ring.c | 7 ++++--- > 1 file changed, 4 insertions(+), 3 deletions(-) > > diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c > index 71e16b53e9c1..1bc290f9ba13 100644 > --- a/drivers/virtio/virtio_ring.c > +++ b/drivers/virtio/virtio_ring.c > @@ -444,11 +444,12 @@ static inline int virtqueue_add_split(struct virtqueue *_vq, > > head = vq->free_head; > > + WARN_ON_ONCE(total_sg > vq->split.vring.num); > + > if (virtqueue_use_indirect(_vq, total_sg)) > desc = alloc_indirect_split(_vq, total_sg, gfp); > else { > desc = NULL; > - WARN_ON_ONCE(total_sg > vq->split.vring.num && !vq->indirect); > } > > if (desc) { > @@ -1118,6 +1119,8 @@ static inline int virtqueue_add_packed(struct virtqueue *_vq, > > BUG_ON(total_sg == 0); > > + WARN_ON_ONCE(total_sg > vq->packed.vring.num); > + > if (virtqueue_use_indirect(_vq, total_sg)) > return virtqueue_add_indirect_packed(vq, sgs, total_sg, > out_sgs, in_sgs, data, gfp); > @@ -1125,8 +1128,6 @@ static inline int virtqueue_add_packed(struct virtqueue *_vq, > head = vq->packed.next_avail_idx; > avail_used_flags = vq->packed.avail_used_flags; > > - WARN_ON_ONCE(total_sg > vq->packed.vring.num && !vq->indirect); > - > desc = vq->packed.vring.desc; > i = head; > descs_used = total_sg;