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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