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=-17.3 required=3.0 tests=BAYES_00,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, URIBL_BLOCKED,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 422C9C43603 for ; Mon, 17 May 2021 14:24:05 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 2667761997 for ; Mon, 17 May 2021 14:24:05 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S239152AbhEQOZU (ORCPT ); Mon, 17 May 2021 10:25:20 -0400 Received: from mx2.suse.de ([195.135.220.15]:50520 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S238856AbhEQOVm (ORCPT ); Mon, 17 May 2021 10:21:42 -0400 X-Virus-Scanned: by amavisd-new at test-mx.suse.de DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.com; s=susede1; t=1621261224; h=from:from:reply-to: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=pBvkavdK2+tEKfPns8/0KtXvMxeeFCb6/eSO70iXjJI=; b=KLTOub7TZSUOtkuHjpjekTAeT7wCeVfOQvosdmBXGcqwk4DiC/5/awqVvT7u7JBOfoHIyE v7KGYFo5pFFclu6Ss7cK58jfDScXMPZZBsPG4CyN9PmNL1hEk1EfZO+4UK8ttQkgRhH+L2 e/oEsvaU+rkOSW2y8kZNRwFlPjxMsro= Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id C0BC3B271; Mon, 17 May 2021 14:20:23 +0000 (UTC) Subject: Re: [PATCH 5/8] xen/netfront: read response from backend only once To: Juergen Gross Cc: Boris Ostrovsky , Stefano Stabellini , "David S. Miller" , Jakub Kicinski , xen-devel@lists.xenproject.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org References: <20210513100302.22027-1-jgross@suse.com> <20210513100302.22027-6-jgross@suse.com> From: Jan Beulich Message-ID: Date: Mon, 17 May 2021 16:20:21 +0200 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:78.0) Gecko/20100101 Thunderbird/78.10.1 MIME-Version: 1.0 In-Reply-To: <20210513100302.22027-6-jgross@suse.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 13.05.2021 12:02, Juergen Gross wrote: > In order to avoid problems in case the backend is modifying a response > on the ring page while the frontend has already seen it, just read the > response into a local buffer in one go and then operate on that buffer > only. > > Signed-off-by: Juergen Gross Reviewed-by: Jan Beulich with one remark: > @@ -830,24 +830,22 @@ static int xennet_get_extras(struct netfront_queue *queue, > break; > } > > - extra = (struct xen_netif_extra_info *) > - RING_GET_RESPONSE(&queue->rx, ++cons); > + RING_COPY_RESPONSE(&queue->rx, ++cons, &extra); > > - if (unlikely(!extra->type || > - extra->type >= XEN_NETIF_EXTRA_TYPE_MAX)) { > + if (unlikely(!extra.type || > + extra.type >= XEN_NETIF_EXTRA_TYPE_MAX)) { > if (net_ratelimit()) > dev_warn(dev, "Invalid extra type: %d\n", > - extra->type); > + extra.type); > err = -EINVAL; > } else { > - memcpy(&extras[extra->type - 1], extra, > - sizeof(*extra)); > + memcpy(&extras[extra.type - 1], &extra, sizeof(extra)); Maybe take the opportunity and switch to (type safe) structure assignment? Jan