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Thu, 11 Jun 2020 18:42:12 +0900 (KST) Received: from KORCO009652 (unknown [12.36.182.243]) by epsmtip1.samsung.com (KnoxPortal) with ESMTPA id 20200611094212epsmtip182a171f8c9b029809fe6b9b4ef1a2590~Xc-7x-6Dp0286202862epsmtip1T; Thu, 11 Jun 2020 09:42:12 +0000 (GMT) From: "Wooyeon Kim" To: "'Dave Martin'" , "'Mark Rutland'" In-Reply-To: <20200608103340.GA31466@arm.com> Subject: RE: [PATCH] arm64: fpsimd: Added API to manage fpsimd state inside kernel Date: Thu, 11 Jun 2020 18:42:12 +0900 Message-ID: <001401d63fd4$95646690$c02d33b0$@samsung.com> MIME-Version: 1.0 X-Mailer: Microsoft Outlook 16.0 Thread-Index: AQGxBksMB01Mym8I2jEMUBwtLj9rogIZEnF2AoMWIKECIyRV0KjnobCQ Content-Language: ko X-Brightmail-Tracker: H4sIAAAAAAAAA01Ta0yTVxjmfN/Xm1qtBeSMZRPrDBOEtWC7AwHHosEmWxwJJFtmBnT0kzJ7 W1sckzjYdA3gBmNhqOU6oZBBJ65WQSKwURaFCgiTkVAYAsVxKReBzMEAV/pBwr/nfd7nOe/7 nJPDxLkFDF9milJHapQSOY++g7hjPSwM0q2OxPON1WHI2FuMo58erBPoR2cHDc1VfQPQVyX3 AJrRX8HRxYo6OhpursbQ38YROmr7uQ9D+vJT6OFlBRq+r6ch89ifNPRHYzEdGft7MHS3uJ2G RibtOPreeQdD1R0NBLpmtwN0y/wDjprWlwl0aVCIyuy1GCp6UEGL8hWbSk1AXJTZQ4jr8oYJ sbkmmy6e7epiiFtKTAzxrcoM8TOngyGea+6ji3MtNUC8aH41ZueH8ggZKZGSGj9SmaSSpiiT I3nvxCYcTxCK+IIgQRh6k+enlCjISN6Jd2OColPkrvw8v3MSeaqLipFotbw3jkVoVKk60k+m 0uoieaRaKlcLBOpgrUShTVUmByepFOECPj9E6FImymXP5mcI9dSetPa8MVom6NmVA1hMyDkK x39ZoueAHUwupwHA/rU+nCoWACw0fUlsqLicRQBLX/hsOUomWzZFjQBOTxcTVDEJoH2u1+2g c47A55ZLYAN7ceJgj42agXMGGHAsv5220WBxgmCjbd5t8HSJchxNbgPBOQT/Lep282xOGDSU mjAK74Xt1xxuHufw4VxXGU7h/bB+phin1vODy+NVNGpwNMwvvI1RGi9YlK13rw05VhZ8OHR3 03ACLpl/ZVDYE07dt2xiX7g420SncDosr/iWQZmzALyabcWoRii0lHS4MNOFD8K2gc3ldsMs 6xqDotkwS8+l1K/B52Ybfev4J1O9+HeAZ9gWzbAtmmFbNMO2COWAqAH7SLVWkUxqQ9Qh29/b DNzfIyC6ARTMzAe3AowJWgFk4jwv9l6fkXguWyr5/DypUSVoUuWkthUIXbedj/t6J6lc/0up SxAIQ0QifpgQCUUhiOfDzjjwKJ7LSZboyLMkqSY1Wz6MyfLNxKKqWI689sxY+cwRsLrWV/ey PHwoTbpw2+lpaXtF//u5FmN13NuHRJ/0/9VQlut/o3VVEHpjcMjjveg94PHTA12/OVrK9NOF 3bba9fdzE9XGQe/+o/+czIlaSitMqIH+ppOWjIKD1mjvwcudzRP3EhdeH/iaIWG9EBK7KzHJ rnzP+tmdx5wfd651rtZ+NDEcez3XUJ26vKjNGtp32ia6cCpAak32eCS+/rjeemX8Yu0Tx1v2 lcMW1US5LIMcWDl++qk6sC+urT7dwyvwZvDKS7Jxbnto4OjVM+gz/25Z7f4zupTS8z2VN0cr Pg13rn0gZJ81E+lFoypFhM12Qb8i/OI/KY/QyiSCAFyjlfwPI5FU56cEAAA= X-Brightmail-Tracker: H4sIAAAAAAAAA02SXUxTZxjH956vlirjUFBeOy2u0QuqVGWYvRpjlqnkXCgq8QYTKw0cAWlr bRGdM7MqwlAzHZualtZROqirFWL5qgXbUEgUUAwFxIhamzqZhsqHMUCG1dgTE+5+ef7/55fn 4uHjwggh4heqi1mtWqGUUAKipVMiTi2eC8rXDs8sQrV+E47+uRchkGWsh0TjdRcAOm1uByhc dhVHZ6wNFAp4bBgarQ1SqOvmEIbKqjPR/fMqFLhbRiJn6BGJBtwmCtUO92PotqmbRMHXIziq HGvBkK3HRSDDyAhAjc7LOLoTmSVQ6dP16K+RGxiqumclfxAxjmsOwFTp+wmm4WKAYJz2Cop5 29fHY7xmB49p/PskMzn2kseMe4Yo5rcmO2DeOcW7FuwVbMpjlYUlrHbN5hxBweREmNC8iTvW fTFE6kH/wnMghg/pdGh+7cXPAQFfSLsANHT8T3CBCPr0Fh7HCTBQ2kVypVEAH7XXkJ8Dil4N p5tKwWdOpPdAS4c/WsLptzxorbiAcRtPADQOVEa1MXQqdPdORDmBzoKujq6oiaBXwpmqh9F5 LL0BGq85MI7jYbfhZXSO02mwz+elOE6GrWETzp23HM7+W0dyV2TA3680Y1wnEVZVlOGXQIJx nso4T2WcpzLOW6kGhB0sYTU6Vb5Kt06TpmaPynQKle6IOl+We0jlBNEXkUpdoN0+IfMBjA98 APJxSWJsfFJQLozNU/x0nNUe2q89omR1PvANn5Akxb43WuRCOl9RzBaxrIbVfkkxfoxIjykL HZL/yr/K9LSVz5JTf5o/pN/PPrDYdvJqBjvuefXY5d5takI/Tw9kb53sLF01lUFLqee265Vf pyXV6DaktPrps4T9D1lq38b6CiBP3zU24R2OyNS9wnCc3b8y48Z3D5Sz38N9i5uHnmVJD9cO hk/5Sk6sKCgGx1ZcpkfFIl9T/KU44W6DNNm99Q3zWBz+JQTfK17k7tGz4Meg/EUgZ8u7jXZ5 VsnNkNOouvvxjDUCZvbC89/KS+ob4Kad2bcs/mWFdcm/to5PzW3PMaRYQuVzm3sP5nufi7Rt a8yeFJx+uqRxh9iRt2xbZrpK0GJt3TZtMxUt9Qy6Owc11yWErkCxToprdYpPDRhL0pEDAAA= X-CMS-MailID: 20200611094212epcas2p4a9d6736f8ad58d796a602739665844ad X-Msg-Generator: CA X-Sendblock-Type: AUTO_CONFIDENTIAL CMS-TYPE: 102P DLP-Filter: Pass X-CFilter-Loop: Reflected X-CMS-RootMailID: 20200605073214epcas2p1576f3f90dbcefaad6180f2559ca5980d References: <20200605073052.23044-1-wooy88.kim@samsung.com> <20200605103705.GD85498@C02TD0UTHF1T.local> <20200608103340.GA31466@arm.com> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20200611_024223_820118_77425E28 X-CRM114-Status: GOOD ( 18.71 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: 'Catalin Marinas' , 'Bhupesh Sharma' , 'Julien Grall' , 'Vincenzo Frascino' , 'Will Deacon' , yhwan.joo@samsung.com, 'Anisse Astier' , 'Marc Zyngier' , 'Allison Randal' , 'Sanghoon Lee' , jihun.kim@samsung.com, 'Kees Cook' , 'Suzuki K Poulose' , 'Wooki Min' , 'Kristina Martsenko' , 'Jeongtae Park' , 'Thomas Gleixner' , linux-arm-kernel@lists.infradead.org, 'Steve Capper' , 'Greg Kroah-Hartman' , linux-kernel@vger.kernel.org, 'James Morse' , 'Sudeep Holla' , dh.han@samsung.com Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org (Previous Mail account information is broken and send again. Sorry for inconvenience) Dear Dave Martin & Mark Rutland Thank you for your kind answer. > On Fri, Jun 05, 2020 at 11:37:05AM +0100, Mark Rutland wrote: > > Hi Wooyeon, > > > > There are a *lot* of people Cc' here, many of whomo will find this > > irrelevant. Please try to keep the Cc list constrained to a > > reasonable number of interested parties. I have adjusted the mailing list according to your opinion. > > Please introduce the problem you are trying to solve in more detail. > > We already have kernel_neon_{begin,end}() for kernel-mode NEON; why > > is that not sufficient for your needs? Please answer this before > > considering other details. > > > > What do you want to use this for? > Ack, this looks supicious. Can you explain why your usecase > _requires_ FPSIMD in hardirq context? > > For now, these functions are strictly for EFI use only and should > never be used by modules. I am in charge of camera driver development in Samsung S.LSI division. In order to guarantee real time processing such as Camera 3A algorithm in current or ongoing projects, prebuilt binary is loaded and used in kernel space, rather than user space. Because the binary is built with other standard library which could use FPSIMD register, kernel API should keep the original FPSIMD state for other user tasks. It is mostly used for internal kernel operation including hardirq context. (ex> hardIRQ context, kernel API called by user, kernel task) In the case of the kernel_neon_begin / kernel_neon_end that you mentioned, there is a limitation that cannot be used in hardirq context. Also, if another kernel task switching occurs while kernel API is being used, fpsimd register corruption may occur. In addition to kernel_neon_* API, It was necessary to add and utilize API considering kernel context. It is for this reason that I have tried to utilize efi_fpsimd_begin/end. Regards Wooyeon Kim _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel