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=-17.6 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 2F901C433DB for ; Mon, 1 Feb 2021 06:47:38 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id F275264E24 for ; Mon, 1 Feb 2021 06:47:37 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232310AbhBAGrE (ORCPT ); Mon, 1 Feb 2021 01:47:04 -0500 Received: from us-smtp-delivery-124.mimecast.com ([216.205.24.124]:37068 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231597AbhBAFls (ORCPT ); Mon, 1 Feb 2021 00:41:48 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1612158016; 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=5mQIIlM5CFm8xeXBVRv4nhYcFaur8L2TXYtvPPpQAxw=; b=dhKJrP/xoCyPJVF3+19azybF6bXigf5S1QqUbP0OcLRkomGIkEA3LySWzpHkifxUuXWbSz rBSsQD3V/+pwLc0faEQwEoL9/26syyuQeVsDNbzTjzXQandpt9gPgc9Aa0cfsJV1Bq2qAX ZiE2kpegDo8REL30KL8gSu1fDwLa3PU= 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-229-vKvb8gjeOfq7lZK4FcopZQ-1; Mon, 01 Feb 2021 00:40:15 -0500 X-MC-Unique: vKvb8gjeOfq7lZK4FcopZQ-1 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 mimecast-mx01.redhat.com (Postfix) with ESMTPS id BD98FCC620; Mon, 1 Feb 2021 05:40:13 +0000 (UTC) Received: from [10.72.13.120] (ovpn-13-120.pek2.redhat.com [10.72.13.120]) by smtp.corp.redhat.com (Postfix) with ESMTP id 476F627CA9; Mon, 1 Feb 2021 05:40:03 +0000 (UTC) Subject: Re: [PATCH RFC v2 03/10] vringh: reset kiov 'consumed' field in __vringh_iov() To: Stefano Garzarella , virtualization@lists.linux-foundation.org Cc: Xie Yongji , "Michael S. Tsirkin" , Laurent Vivier , Stefan Hajnoczi , linux-kernel@vger.kernel.org, Max Gurtovoy , kvm@vger.kernel.org References: <20210128144127.113245-1-sgarzare@redhat.com> <20210128144127.113245-4-sgarzare@redhat.com> From: Jason Wang Message-ID: <62bb2e93-4ac3-edf5-2baa-4c2be8257cf0@redhat.com> Date: Mon, 1 Feb 2021 13:40:01 +0800 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.10.0 MIME-Version: 1.0 In-Reply-To: <20210128144127.113245-4-sgarzare@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 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2021/1/28 下午10:41, Stefano Garzarella wrote: > __vringh_iov() overwrites the contents of riov and wiov, in fact it > resets the 'i' and 'used' fields, but also the consumed field should > be reset to avoid an inconsistent state. > > Signed-off-by: Stefano Garzarella I had a question(I remember we had some discussion like this but I forget the conclusion): I see e.g in vringh_getdesc_kern() it has the following comment: /*  * Note that you may need to clean up riov and wiov, even on error!  */ So it looks to me the correct way is to call vringh_kiov_cleanup() before? Thanks > --- > drivers/vhost/vringh.c | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > > diff --git a/drivers/vhost/vringh.c b/drivers/vhost/vringh.c > index f68122705719..bee63d68201a 100644 > --- a/drivers/vhost/vringh.c > +++ b/drivers/vhost/vringh.c > @@ -290,9 +290,9 @@ __vringh_iov(struct vringh *vrh, u16 i, > return -EINVAL; > > if (riov) > - riov->i = riov->used = 0; > + riov->i = riov->used = riov->consumed = 0; > if (wiov) > - wiov->i = wiov->used = 0; > + wiov->i = wiov->used = wiov->consumed = 0; > > for (;;) { > void *addr;