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=-7.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS 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 ABFACC10F0E for ; Tue, 9 Apr 2019 09:01:09 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 8060A20883 for ; Tue, 9 Apr 2019 09:01:09 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726592AbfDIJBH (ORCPT ); Tue, 9 Apr 2019 05:01:07 -0400 Received: from mx1.redhat.com ([209.132.183.28]:41602 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726035AbfDIJBH (ORCPT ); Tue, 9 Apr 2019 05:01:07 -0400 Received: from smtp.corp.redhat.com (int-mx08.intmail.prod.int.phx2.redhat.com [10.5.11.23]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id B564E2D7F3; Tue, 9 Apr 2019 09:01:06 +0000 (UTC) Received: from [10.72.12.67] (ovpn-12-67.pek2.redhat.com [10.72.12.67]) by smtp.corp.redhat.com (Postfix) with ESMTP id E65FA272C0; Tue, 9 Apr 2019 09:01:01 +0000 (UTC) Subject: Re: [PATCH] virtio: Honour 'may_reduce_num' in vring_create_virtqueue To: Cornelia Huck , "Michael S . Tsirkin" Cc: Halil Pasic , virtualization@lists.linux-foundation.org, kvm@vger.kernel.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org References: <20190408123322.24086-1-cohuck@redhat.com> From: Jason Wang Message-ID: <9b3d1789-33e1-3ad5-18cd-cacefec8bbb2@redhat.com> Date: Tue, 9 Apr 2019 17:00:59 +0800 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.6.1 MIME-Version: 1.0 In-Reply-To: <20190408123322.24086-1-cohuck@redhat.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit Content-Language: en-US X-Scanned-By: MIMEDefang 2.84 on 10.5.11.23 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.30]); Tue, 09 Apr 2019 09:01:06 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2019/4/8 下午8:33, Cornelia Huck wrote: > vring_create_virtqueue() allows the caller to specify via the > may_reduce_num parameter whether the vring code is allowed to > allocate a smaller ring than specified. > > However, the split ring allocation code tries to allocate a > smaller ring on allocation failure regardless of what the > caller specified. This may cause trouble for e.g. virtio-pci > in legacy mode, which does not support ring resizing. (The > packed ring code does not resize in any case.) > > Let's fix this by bailing out immediately in the split ring code > if the requested size cannot be allocated and may_reduce_num has > not been specified. > > While at it, fix a typo in the usage instructions. > > Fixes: 2a2d1382fe9d ("virtio: Add improved queue allocation API") > Cc: stable@vger.kernel.org # v4.6+ > Signed-off-by: Cornelia Huck > --- > drivers/virtio/virtio_ring.c | 2 ++ > include/linux/virtio_ring.h | 2 +- > 2 files changed, 3 insertions(+), 1 deletion(-) > > diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c > index 18846afb39da..5df92c308286 100644 > --- a/drivers/virtio/virtio_ring.c > +++ b/drivers/virtio/virtio_ring.c > @@ -882,6 +882,8 @@ static struct virtqueue *vring_create_virtqueue_split( > GFP_KERNEL|__GFP_NOWARN|__GFP_ZERO); > if (queue) > break; > + if (!may_reduce_num) > + return NULL; > } > > if (!num) > diff --git a/include/linux/virtio_ring.h b/include/linux/virtio_ring.h > index fab02133a919..3dc70adfe5f5 100644 > --- a/include/linux/virtio_ring.h > +++ b/include/linux/virtio_ring.h > @@ -63,7 +63,7 @@ struct virtqueue; > /* > * Creates a virtqueue and allocates the descriptor ring. If > * may_reduce_num is set, then this may allocate a smaller ring than > - * expected. The caller should query virtqueue_get_ring_size to learn > + * expected. The caller should query virtqueue_get_vring_size to learn > * the actual size of the ring. > */ > struct virtqueue *vring_create_virtqueue(unsigned int index, Acked-by: Jason Wang