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[134.134.136.65]) by mx.google.com with ESMTPS id v27si36625868pgn.14.2019.08.01.09.45.06 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 01 Aug 2019 09:45:06 -0700 (PDT) Received-SPF: pass (google.com: domain of dave.hansen@intel.com designates 134.134.136.65 as permitted sender) client-ip=134.134.136.65; Authentication-Results: mx.google.com; spf=pass (google.com: domain of dave.hansen@intel.com designates 134.134.136.65 as permitted sender) smtp.mailfrom=dave.hansen@intel.com; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=intel.com X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from orsmga003.jf.intel.com ([10.7.209.27]) by orsmga103.jf.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 01 Aug 2019 09:45:06 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.64,334,1559545200"; d="scan'208";a="175307534" Received: from ray.jf.intel.com (HELO [10.7.201.140]) ([10.7.201.140]) by orsmga003.jf.intel.com with ESMTP; 01 Aug 2019 09:45:06 -0700 Subject: Re: [PATCH v19 02/15] arm64: Introduce prctl() options to control the tagged user addresses ABI To: Kevin Brodsky , Andrey Konovalov , linux-arm-kernel@lists.infradead.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, amd-gfx@lists.freedesktop.org, dri-devel@lists.freedesktop.org, linux-rdma@vger.kernel.org, linux-media@vger.kernel.org, kvm@vger.kernel.org, linux-kselftest@vger.kernel.org Cc: Catalin Marinas , Vincenzo Frascino , Will Deacon , Mark Rutland , Andrew Morton , Greg Kroah-Hartman , Kees Cook , Yishai Hadas , Felix Kuehling , Alexander Deucher , Christian Koenig , Mauro Carvalho Chehab , Jens Wiklander , Alex Williamson , Leon Romanovsky , Luc Van Oostenryck , Dave Martin , Khalid Aziz , enh , Jason Gunthorpe , Christoph Hellwig , Dmitry Vyukov , Kostya Serebryany , Evgeniy Stepanov , Lee Smith , Ramana Radhakrishnan , Jacob Bramley , Ruben Ayrapetyan , Robin Murphy , Szabolcs Nagy References: <1c05651c53f90d07e98ee4973c2786ccf315db12.1563904656.git.andreyknvl@google.com> <7a34470c-73f0-26ac-e63d-161191d4b1e4@intel.com> <2b274c6f-6023-8eb8-5a86-507e6000e13d@arm.com> From: Dave Hansen Openpgp: preference=signencrypt Autocrypt: addr=dave.hansen@intel.com; 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Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.8.0 MIME-Version: 1.0 In-Reply-To: <2b274c6f-6023-8eb8-5a86-507e6000e13d@arm.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit 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 8/1/19 5:38 AM, Kevin Brodsky wrote: > This patch series only changes what is allowed or not at the syscall > interface. It does not change the address space size. On arm64, TBI (Top > Byte Ignore) has always been enabled for userspace, so it has never been > possible to use the upper 8 bits of user pointers for addressing. Oh, so does the address space that's available already chop that out? > If other architectures were to support a similar functionality, then I > agree that a common and more generic interface (if needed) would be > helpful, but as it stands this is an arm64-specific prctl, and on arm64 > the address tag is defined by the architecture as bits [63:56]. It should then be an arch_prctl(), no?