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=-5.6 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=no 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 BB52FC433E1 for ; Sat, 15 Aug 2020 17:31:11 +0000 (UTC) Received: from lists.xenproject.org (lists.xenproject.org [192.237.175.120]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 8DD4023B30 for ; Sat, 15 Aug 2020 17:31:11 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=xen.org header.i=@xen.org header.b="4eV1aXoP" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 8DD4023B30 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=xen.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=xen-devel-bounces@lists.xenproject.org Received: from localhost ([127.0.0.1] helo=lists.xenproject.org) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1k7019-0004js-Eq; Sat, 15 Aug 2020 17:30:55 +0000 Received: from us1-rack-iad1.inumbo.com ([172.99.69.81]) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1k7018-0004jn-6Z for xen-devel@lists.xenproject.org; Sat, 15 Aug 2020 17:30:54 +0000 X-Inumbo-ID: c84d8f31-a07c-441c-a620-477a9040542a Received: from mail.xenproject.org (unknown [104.130.215.37]) by us1-rack-iad1.inumbo.com (Halon) with ESMTPS id c84d8f31-a07c-441c-a620-477a9040542a; Sat, 15 Aug 2020 17:30:53 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=xen.org; s=20200302mail; h=Content-Transfer-Encoding:Content-Type:In-Reply-To: MIME-Version:Date:Message-ID:From:References:Cc:To:Subject; bh=yJqxU9lMiE+a3Fv429IhMJzKSz4RYuQrf9/UIaAUCFg=; b=4eV1aXoPWlabsf2WhHFG2x4WzO QjQTNcyv9U9q2WiodAlijbZ0aT+xrllIIuc2e/e9eqaaaRazaSd0hH4vznvC0YL5cxh3VESS1Pt22 96jP+G9+wtzDHTu5DbbmeFiElzcQnYoD7uX2rupKFmGpYvoRVEGZDj6SNoA1Hx8Qvagg=; Received: from xenbits.xenproject.org ([104.239.192.120]) by mail.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1k700z-0006Pu-2R; Sat, 15 Aug 2020 17:30:45 +0000 Received: from [54.239.6.185] (helo=a483e7b01a66.ant.amazon.com) by xenbits.xenproject.org with esmtpsa (TLS1.3:ECDHE_RSA_AES_128_GCM_SHA256:128) (Exim 4.92) (envelope-from ) id 1k700y-00030y-M6; Sat, 15 Aug 2020 17:30:44 +0000 Subject: Re: [RFC PATCH V1 01/12] hvm/ioreq: Make x86's IOREQ feature common To: Oleksandr Tyshchenko , xen-devel@lists.xenproject.org Cc: Kevin Tian , Stefano Stabellini , Jun Nakajima , Wei Liu , Paul Durrant , Andrew Cooper , Ian Jackson , George Dunlap , Tim Deegan , Oleksandr Tyshchenko , Julien Grall , Jan Beulich , =?UTF-8?Q?Roger_Pau_Monn=c3=a9?= References: <1596478888-23030-1-git-send-email-olekstysh@gmail.com> <1596478888-23030-2-git-send-email-olekstysh@gmail.com> From: Julien Grall Message-ID: <73ab810e-f7c0-14cd-c400-24ddeb79eda5@xen.org> Date: Sat, 15 Aug 2020 18:30:41 +0100 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:68.0) Gecko/20100101 Thunderbird/68.11.0 MIME-Version: 1.0 In-Reply-To: <1596478888-23030-2-git-send-email-olekstysh@gmail.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-GB Content-Transfer-Encoding: 7bit X-BeenThere: xen-devel@lists.xenproject.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Xen developer discussion List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Errors-To: xen-devel-bounces@lists.xenproject.org Sender: "Xen-devel" Hi Oleksandr, On 03/08/2020 19:21, Oleksandr Tyshchenko wrote: > +static int hvm_send_buffered_ioreq(struct hvm_ioreq_server *s, ioreq_t *p) > +{ [...] > + /* Canonicalize read/write pointers to prevent their overflow. */ > + while ( (s->bufioreq_handling == HVM_IOREQSRV_BUFIOREQ_ATOMIC) && > + qw++ < IOREQ_BUFFER_SLOT_NUM && > + pg->ptrs.read_pointer >= IOREQ_BUFFER_SLOT_NUM ) > + { > + union bufioreq_pointers old = pg->ptrs, new; > + unsigned int n = old.read_pointer / IOREQ_BUFFER_SLOT_NUM; > + > + new.read_pointer = old.read_pointer - n * IOREQ_BUFFER_SLOT_NUM; > + new.write_pointer = old.write_pointer - n * IOREQ_BUFFER_SLOT_NUM; > + cmpxchg(&pg->ptrs.full, old.full, new.full); While working on the implementation of cmpxchg(), I realized the operation will happen on memory shared with a the emulator. This will need to be switched to guest_cmpxchg64() to prevent a domain to DoS Xen on Arm. I looked at the rest of the IOREQ and didn't notice any other example. Cheers, -- Julien Grall