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[97.126.123.70]) by smtp.gmail.com with ESMTPSA id a3sm29439695pfi.161.2020.03.11.15.17.56 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 11 Mar 2020 15:17:57 -0700 (PDT) Subject: Re: [PATCH v2 19/19] arm64: mte: Add Memory Tagging Extension documentation To: Catalin Marinas , linux-arm-kernel@lists.infradead.org Cc: linux-arch@vger.kernel.org, Richard Earnshaw , Szabolcs Nagy , Andrey Konovalov , Kevin Brodsky , Peter Collingbourne , linux-mm@kvack.org, Vincenzo Frascino , Will Deacon References: <20200226180526.3272848-1-catalin.marinas@arm.com> <20200226180526.3272848-20-catalin.marinas@arm.com> From: Richard Henderson Message-ID: <0857cca0-9f75-398d-e755-f645d2d8a594@linaro.org> Date: Wed, 11 Mar 2020 15:17:54 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.4.1 MIME-Version: 1.0 In-Reply-To: <20200226180526.3272848-20-catalin.marinas@arm.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On 2/26/20 10:05 AM, Catalin Marinas wrote: > + /* > + * From include/uapi/linux/prctl.h > + */ > + #define PR_SET_TAGGED_ADDR_CTRL 55 > + #define PR_GET_TAGGED_ADDR_CTRL 56 > + # define PR_TAGGED_ADDR_ENABLE (1UL << 0) > + # define PR_MTE_TCF_SHIFT 1 > + # define PR_MTE_TCF_NONE (0UL << PR_MTE_TCF_SHIFT) > + # define PR_MTE_TCF_SYNC (1UL << PR_MTE_TCF_SHIFT) > + # define PR_MTE_TCF_ASYNC (2UL << PR_MTE_TCF_SHIFT) > + # define PR_MTE_TCF_MASK (3UL << PR_MTE_TCF_SHIFT) > + # define PR_MTE_TAG_SHIFT 3 > + # define PR_MTE_TAG_MASK (0xffffUL << PR_MTE_TAG_SHIFT) Is there a reason not to include TCMA into the set of bits that userland can control with this prcrl? I know that ordinarily TCR_ELx requires expensive syncing, but for this particular field there is a note about "software may change this control bit on a context switch". Which I take to mean that the usual TLB-related syncing may be omitted. r~