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 DC992C433E0 for ; Tue, 23 Mar 2021 02:39:51 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id AE14C619AB for ; Tue, 23 Mar 2021 02:39:51 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229822AbhCWCjS (ORCPT ); Mon, 22 Mar 2021 22:39:18 -0400 Received: from us-smtp-delivery-124.mimecast.com ([216.205.24.124]:46356 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229548AbhCWCjF (ORCPT ); Mon, 22 Mar 2021 22:39:05 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1616467144; 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=VioJuhqdUyJCQVP29PR+eSQQoRfuRxX0mBNikg8J2Ak=; b=N37SljRPTa4sBErU7VYDE7kwE6MxIS5k1T8BgDiCjHj0LjD+oX7j7hx8PPM46n/cb4POU0 1kMsIL4pTwtZ99bAUnXUNgSE01r+0bvAWgwkSZEFaEv632nWbD9JmAop3QNRwrl1basvtk fuCRjTsE34UWRYiP4CNws/ynyTkXQGQ= 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-525-6Vei-IDwNMa_H6gVgguhBA-1; Mon, 22 Mar 2021 22:39:02 -0400 X-MC-Unique: 6Vei-IDwNMa_H6gVgguhBA-1 Received: from smtp.corp.redhat.com (int-mx02.intmail.prod.int.phx2.redhat.com [10.5.11.12]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 49B171009456; Tue, 23 Mar 2021 02:39:01 +0000 (UTC) Received: from wangxiaodeMacBook-Air.local (ovpn-12-238.pek2.redhat.com [10.72.12.238]) by smtp.corp.redhat.com (Postfix) with ESMTP id 5907760C5F; Tue, 23 Mar 2021 02:38:43 +0000 (UTC) Subject: Re: [PATCH 1/3] virtio_ring: always warn when descriptor chain exceeds queue size To: "Michael S. Tsirkin" Cc: Connor Kuehl , virtio-fs@redhat.com, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, virtualization@lists.linux-foundation.org, stefanha@redhat.com, vgoyal@redhat.com, miklos@szeredi.hu References: <20210318135223.1342795-1-ckuehl@redhat.com> <20210318135223.1342795-2-ckuehl@redhat.com> <20210322041414-mutt-send-email-mst@kernel.org> From: Jason Wang Message-ID: Date: Tue, 23 Mar 2021 10:38:41 +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: <20210322041414-mutt-send-email-mst@kernel.org> Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit X-Scanned-By: MIMEDefang 2.79 on 10.5.11.12 Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org 在 2021/3/22 下午4:17, Michael S. Tsirkin 写道: > On Mon, Mar 22, 2021 at 11:22:15AM +0800, Jason Wang wrote: >> 在 2021/3/18 下午9:52, Connor Kuehl 写道: >>> 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 > It would be quite strange for packed and split to differ here: > so for packed would you say there's no limit on # of descriptors at all? > > I am guessing I just forgot to move this part from > the format specific to the common part of the spec. > > This needs discussion in the TC mailing list - want to start a thread > there? Will do. 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;