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Tue, 28 Sep 2021 19:15:08 -0700 From: "Luck, Tony" To: "Yu, Fenghua" Subject: RE: [PATCH 4/8] x86/traps: Demand-populate PASID MSR via #GP Thread-Topic: [PATCH 4/8] x86/traps: Demand-populate PASID MSR via #GP Thread-Index: AQHXrlppUXtiT4Ul9UCq0y1lpkQn1quyuuKAgAWuhwCAAKRkgIAAyOqAgAB9aAD//53xAIAAfQEA//+wWACAAICAgP//j4cAABJzk4AADh9DwA== Date: Wed, 29 Sep 2021 02:15:08 +0000 Message-ID: <9e12eba3e78e4bc98d550943ff639ebe@intel.com> References: <20210920192349.2602141-5-fenghua.yu@intel.com> <1aae375d-3cd4-4ab8-9c64-9e387916e6c0@www.fastmail.com> <035290e6-d914-a113-ea6c-e845d71069cf@intel.com> <3f97b77e-a609-997b-3be7-f44ff7312b0d@intel.com> <840148c7b70f4358852c4f1ccbc5d567@intel.com> In-Reply-To: <840148c7b70f4358852c4f1ccbc5d567@intel.com> Accept-Language: en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: dlp-product: dlpe-windows dlp-reaction: no-action dlp-version: 11.6.200.16 x-originating-ip: [10.1.200.100] MIME-Version: 1.0 Cc: "Shankar, Ravi V" , "Jiang, Dave" , "Raj, Ashok" , "Peter Zijlstra \(Intel\)" , the arch/x86 maintainers , Linux Kernel Mailing List , "Hansen, Dave" , "iommu@lists.linux-foundation.org" , Ingo Molnar , Borislav Petkov , "Pan, Jacob jun" , Andy Lutomirski , Josh Poimboeuf , Thomas Gleixner X-BeenThere: iommu@lists.linux-foundation.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: Development issues for Linux IOMMU support List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: iommu-bounces@lists.linux-foundation.org Sender: "iommu" >> if (!(xsave->header.xfeatures & fmask)) { >> xsave->header.xfeatures |= fmask; //<<<<< >> xsaves(xsave, fmask); >> } > > I'm not sure why the FPU state is initialized here. > > For updating the PASID state, it's unnecessary to init the PASID state. > > Maybe it is necessary in other cases? Dave had suggested initializing feature state when it is unknown (could be garbage). This is my attempt to follow that guidance. I'm not confident that my tests for "is the state in registers, in memory, or is garbage" really capture all the cases. -Tony _______________________________________________ iommu mailing list iommu@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/iommu 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 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 6BA97C433F5 for ; Wed, 29 Sep 2021 02:15:27 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 4D9E1613DB for ; Wed, 29 Sep 2021 02:15:27 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S243731AbhI2CRF convert rfc822-to-8bit (ORCPT ); Tue, 28 Sep 2021 22:17:05 -0400 Received: from mga17.intel.com ([192.55.52.151]:63690 "EHLO mga17.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S243628AbhI2CRD (ORCPT ); Tue, 28 Sep 2021 22:17:03 -0400 X-IronPort-AV: E=McAfee;i="6200,9189,10121"; a="204994181" X-IronPort-AV: E=Sophos;i="5.85,331,1624345200"; d="scan'208";a="204994181" Received: from fmsmga003.fm.intel.com ([10.253.24.29]) by fmsmga107.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 28 Sep 2021 19:15:09 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.85,331,1624345200"; d="scan'208";a="554425552" Received: from fmsmsx601.amr.corp.intel.com ([10.18.126.81]) by FMSMGA003.fm.intel.com with ESMTP; 28 Sep 2021 19:15:09 -0700 Received: from fmsmsx611.amr.corp.intel.com (10.18.126.91) by fmsmsx601.amr.corp.intel.com (10.18.126.81) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2242.12; Tue, 28 Sep 2021 19:15:09 -0700 Received: from fmsmsx610.amr.corp.intel.com (10.18.126.90) by fmsmsx611.amr.corp.intel.com (10.18.126.91) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2242.12; Tue, 28 Sep 2021 19:15:08 -0700 Received: from fmsmsx610.amr.corp.intel.com ([10.18.126.90]) by fmsmsx610.amr.corp.intel.com ([10.18.126.90]) with mapi id 15.01.2242.012; Tue, 28 Sep 2021 19:15:08 -0700 From: "Luck, Tony" To: "Yu, Fenghua" CC: "Hansen, Dave" , Andy Lutomirski , Thomas Gleixner , Ingo Molnar , Borislav Petkov , "Peter Zijlstra (Intel)" , Lu Baolu , Joerg Roedel , Josh Poimboeuf , "Jiang, Dave" , "Pan, Jacob jun" , "Raj, Ashok" , "Shankar, Ravi V" , "iommu@lists.linux-foundation.org" , "the arch/x86 maintainers" , Linux Kernel Mailing List Subject: RE: [PATCH 4/8] x86/traps: Demand-populate PASID MSR via #GP Thread-Topic: [PATCH 4/8] x86/traps: Demand-populate PASID MSR via #GP Thread-Index: AQHXrlppUXtiT4Ul9UCq0y1lpkQn1quyuuKAgAWuhwCAAKRkgIAAyOqAgAB9aAD//53xAIAAfQEA//+wWACAAICAgP//j4cAABJzk4AADh9DwA== Date: Wed, 29 Sep 2021 02:15:08 +0000 Message-ID: <9e12eba3e78e4bc98d550943ff639ebe@intel.com> References: <20210920192349.2602141-5-fenghua.yu@intel.com> <1aae375d-3cd4-4ab8-9c64-9e387916e6c0@www.fastmail.com> <035290e6-d914-a113-ea6c-e845d71069cf@intel.com> <3f97b77e-a609-997b-3be7-f44ff7312b0d@intel.com> <840148c7b70f4358852c4f1ccbc5d567@intel.com> In-Reply-To: <840148c7b70f4358852c4f1ccbc5d567@intel.com> Accept-Language: en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: dlp-product: dlpe-windows dlp-reaction: no-action dlp-version: 11.6.200.16 x-originating-ip: [10.1.200.100] Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 8BIT MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org >> if (!(xsave->header.xfeatures & fmask)) { >> xsave->header.xfeatures |= fmask; //<<<<< >> xsaves(xsave, fmask); >> } > > I'm not sure why the FPU state is initialized here. > > For updating the PASID state, it's unnecessary to init the PASID state. > > Maybe it is necessary in other cases? Dave had suggested initializing feature state when it is unknown (could be garbage). This is my attempt to follow that guidance. I'm not confident that my tests for "is the state in registers, in memory, or is garbage" really capture all the cases. -Tony