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=-9.6 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=ham 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 8051BC433EF for ; Tue, 7 Sep 2021 10:01:41 +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 43A6061106 for ; Tue, 7 Sep 2021 10:01:41 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.1 mail.kernel.org 43A6061106 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=xen.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=lists.xenproject.org Received: from list by lists.xenproject.org with outflank-mailman.180715.327479 (Exim 4.92) (envelope-from ) id 1mNXuv-0008Av-2H; Tue, 07 Sep 2021 10:01:25 +0000 X-Outflank-Mailman: Message body and most headers restored to incoming version Received: by outflank-mailman (output) from mailman id 180715.327479; Tue, 07 Sep 2021 10:01:25 +0000 Received: from localhost ([127.0.0.1] helo=lists.xenproject.org) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1mNXuu-0008Ao-Uz; Tue, 07 Sep 2021 10:01:24 +0000 Received: by outflank-mailman (input) for mailman id 180715; Tue, 07 Sep 2021 10:01:24 +0000 Received: from mail.xenproject.org ([104.130.215.37]) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1mNXuu-0008Ai-0M for xen-devel@lists.xenproject.org; Tue, 07 Sep 2021 10:01:24 +0000 Received: from xenbits.xenproject.org ([104.239.192.120]) by mail.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1mNXul-00019S-DD; Tue, 07 Sep 2021 10:01:15 +0000 Received: from [54.239.6.187] (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 1mNXul-0000A5-6A; Tue, 07 Sep 2021 10:01:15 +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=PkCgRNrbFPgPtKA37oxT20cFd+oz/vvNiad1HjOCvq0=; b=GV/ghNPTj7NjTiTquDGTwIIuK3 wHp+5s0AAtFICUwV6aX8CXeqpg8pNsNqw6jSWj0C248h9LtaaLOHaGk6rA11l5GW2uzkdB7kYFADy W6efVik1PCy1enFFxYA1QfdowzGGbOLUXpvl8qFaauFHQVxeJq1w2IcaRE35MvORsOTo=; Subject: Re: [PATCH v1 01/14] xen/pci: Refactor MSI code that implements MSI functionality within XEN To: Rahul Singh Cc: xen-devel , Bertrand Marquis , Jan Beulich , Andrew Cooper , =?UTF-8?Q?Roger_Pau_Monn=c3=a9?= , Wei Liu , George Dunlap , Ian Jackson , Stefano Stabellini , Paul Durrant , Daniel De Graaf , "Daniel P. Smith" References: <9022cf38-532f-05bd-d78d-50f46cdbd8f5@xen.org> <4909CE53-15AE-4A6D-A32D-69B5E6AC6DDD@arm.com> From: Julien Grall Message-ID: <10505763-238a-1a9b-88cc-b19312a16e44@xen.org> Date: Tue, 7 Sep 2021 11:01:12 +0100 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:78.0) Gecko/20100101 Thunderbird/78.13.0 MIME-Version: 1.0 In-Reply-To: <4909CE53-15AE-4A6D-A32D-69B5E6AC6DDD@arm.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-GB Content-Transfer-Encoding: 7bit On 19/08/2021 15:16, Rahul Singh wrote: > Hi Julien, Hi Rahul, Sorry for the late reply. >> On 19 Aug 2021, at 1:18 pm, Julien Grall wrote: >> >> Hi Rahul, >> >> On 19/08/2021 13:02, Rahul Singh wrote: >>> MSI code that implements MSI functionality to support MSI within XEN is >>> not usable on ARM. Move the code under CONFIG_HAS_PCI_MSI flag to gate >> >> Can you clarify what you mean by not usable? Is it because we lack of support or we have no plan to use it? > > We have no plan to use it. Code moved to CONFIG_HAS_PCI_MSI will only be required for ARM if we I read "not usable", as the code doesn't yet work on Arm. This is quite possible, but from you wrote the main reason is that the code is not necessary yet (see below) on Arm. > decide to support PCI device access (PCI MSI interrupt support) within XEN. As of now, we are planning > to add support for PCI device access for DOM0/DOMU guests not for XEN. This is probably going to happen sooner rather than later as, AFAICT, there are SMMUs out which signals using MSIs. But, AFAICT, this code would also be used if we need to manage the MSIs in Xen on behalf of the guest (such as if the platform is using GICv2m). That said, I would be fine with gating the MSI code behind a new config. However, I think the commit message wants to be clarified into why we don't need the option. Maybe something like: "On Arm, the inital plan is to only support GICv3 ITS which doesn't require us to manage the MSIs because the HW will protect against spoofing. Introduce a new option XXXX to protect the MSI code. " Cheers, -- Julien Grall