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=-7.3 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 6FF61C433ED for ; Fri, 16 Apr 2021 16:09:12 +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 1D1BC610CE for ; Fri, 16 Apr 2021 16:09:12 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 1D1BC610CE 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 list by lists.xenproject.org with outflank-mailman.111910.213987 (Exim 4.92) (envelope-from ) id 1lXR1j-0001at-8l; Fri, 16 Apr 2021 16:09:03 +0000 X-Outflank-Mailman: Message body and most headers restored to incoming version Received: by outflank-mailman (output) from mailman id 111910.213987; Fri, 16 Apr 2021 16:09:03 +0000 Received: from localhost ([127.0.0.1] helo=lists.xenproject.org) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1lXR1j-0001am-5q; Fri, 16 Apr 2021 16:09:03 +0000 Received: by outflank-mailman (input) for mailman id 111910; Fri, 16 Apr 2021 16:09:02 +0000 Received: from mail.xenproject.org ([104.130.215.37]) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1lXR1i-0001ah-PV for xen-devel@lists.xenproject.org; Fri, 16 Apr 2021 16:09:02 +0000 Received: from xenbits.xenproject.org ([104.239.192.120]) by mail.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1lXR1h-0001uS-Mf; Fri, 16 Apr 2021 16:09:01 +0000 Received: from [54.239.6.186] (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 1lXR1h-00085X-Fw; Fri, 16 Apr 2021 16:09:01 +0000 X-BeenThere: xen-devel@lists.xenproject.org List-Id: Xen developer discussion List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Errors-To: xen-devel-bounces@lists.xenproject.org Precedence: list Sender: "Xen-devel" 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=orFF7aaepF8eXlbSp7s24PPTR892b/JKbx/l2YTPOTg=; b=kqAogKeYO18B4HmRnx+KdYbDuy X6OSPDuL3NSVGaI4DDcxKv+z2JE4ZEaHpC2a+RJwgktKwF9F/oFtCVcXOdwQSfWMdwevBXYRewQBf uu/DzDHjUZCnvGtpO9t4DZ4KN3NPOtxfxiu6Hd0piCC73fEz5PWbJaIb6AlzAkJnTLaE=; Subject: Re: [PATCH] xen/arm: smmuv1: Revert associating the group pointer with the S2CR To: Rahul Singh Cc: xen-devel , Bertrand Marquis , Stefano Stabellini , Volodymyr Babchuk References: <6e75d112-6cc1-4b7c-9751-4064b3250dbf@xen.org> <8569c856-8838-e5d1-b653-e7eb476dacdc@xen.org> <4C9CE5FC-551A-4F26-B975-FC7F33877FF2@arm.com> From: Julien Grall Message-ID: <78c30978-c3be-4357-fecc-5b2f24bf563f@xen.org> Date: Fri, 16 Apr 2021 17:08:59 +0100 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:78.0) Gecko/20100101 Thunderbird/78.9.1 MIME-Version: 1.0 In-Reply-To: <4C9CE5FC-551A-4F26-B975-FC7F33877FF2@arm.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-GB Content-Transfer-Encoding: 8bit On 16/04/2021 17:05, Rahul Singh wrote: >> On 16 Apr 2021, at 4:23 pm, Julien Grall wrote: >> >> >> >> On 16/04/2021 16:01, Rahul Singh wrote: >>> Hi Julien, >> >> Hi Rahul, >> >>>> On 16 Apr 2021, at 3:35 pm, Julien Grall wrote: >>>> >>>> Hi, >>>> >>>> On 16/04/2021 12:25, Rahul Singh wrote: >>>>> Revert the code that associates the group pointer with the S2CR as this >>>>> code causing an issue when the SMMU device has more than one master >>>>> device. >>>> >>>> It is not clear to me why this change was first added. Are we missing any feature when reverting it? >>> This feature was added when we backported the code from Linux to fix the stream match conflict issue >>> as part of commit "xen/arm: smmuv1: Intelligent SMR allocation”. >>> This is an extra feature added to allocate IOMMU group based on stream-id. If two device has the >>> same stream-id then we assign those devices to the same group. >> >> If we revert the patch, then it would not be possible to use the SMMU if two devices use the same stream-id. Is that correct? > > No. If we revert the patch we can use the SMMU if two devices use the same stream-id without any issue but each device will be in a separate group.This is same behaviour before the code is merged. Ok. So there is no change in behavior. Good. Can you propose a commit message clarifying that? OOI why was the code added if it doesn't make any difference? Anyway, thanks for the explanation! Cheers, -- Julien Grall