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[217.140.110.172]) by mx.google.com with ESMTP id l42si24788948edc.120.2019.08.02.03.08.39 for ; Fri, 02 Aug 2019 03:08:40 -0700 (PDT) Received-SPF: pass (google.com: domain of catalin.marinas@arm.com designates 217.140.110.172 as permitted sender) client-ip=217.140.110.172; Authentication-Results: mx.google.com; spf=pass (google.com: domain of catalin.marinas@arm.com designates 217.140.110.172 as permitted sender) smtp.mailfrom=catalin.marinas@arm.com Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 2C9EB344; Fri, 2 Aug 2019 03:08:39 -0700 (PDT) Received: from arrakis.emea.arm.com (arrakis.cambridge.arm.com [10.1.196.78]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id B1D323F71F; Fri, 2 Aug 2019 03:08:37 -0700 (PDT) Date: Fri, 2 Aug 2019 11:08:35 +0100 From: Catalin Marinas To: Dave Hansen Cc: Vincenzo Frascino , linux-arm-kernel@lists.infradead.org, linux-doc@vger.kernel.org, linux-mm@kvack.org, linux-arch@vger.kernel.org, linux-kselftest@vger.kernel.org, linux-kernel@vger.kernel.org, Will Deacon , Andrey Konovalov , Szabolcs Nagy Subject: Re: [PATCH v6 1/2] arm64: Define Documentation/arm64/tagged-address-abi.rst Message-ID: <20190802100835.GA4175@arrakis.emea.arm.com> References: <20190725135044.24381-1-vincenzo.frascino@arm.com> <20190725135044.24381-2-vincenzo.frascino@arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.10.1 (2018-07-13) 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: Hi Dave, On Wed, Jul 31, 2019 at 09:43:46AM -0700, Dave Hansen wrote: > On 7/25/19 6:50 AM, Vincenzo Frascino wrote: > > With the relaxed ABI proposed through this document, it is now possible > > to pass tagged pointers to the syscalls, when these pointers are in > > memory ranges obtained by an anonymous (MAP_ANONYMOUS) mmap(). > > I don't see a lot of description of why this restriction is necessary. > What's the problem with supporting MAP_SHARED? We could support MAP_SHARED | MAP_ANONYMOUS (and based on some internal discussions, this would be fine with the hardware memory tagging as well). What we don't want in the ABI is to support file mmap() for top-byte-ignore (or MTE). If you see a use-case, please let us know. -- Catalin