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[134.134.136.100]) by mx.google.com with ESMTPS id f10si1822617pjw.89.2019.07.31.09.43.47 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 31 Jul 2019 09:43:47 -0700 (PDT) Received-SPF: pass (google.com: domain of dave.hansen@intel.com designates 134.134.136.100 as permitted sender) client-ip=134.134.136.100; Authentication-Results: mx.google.com; spf=pass (google.com: domain of dave.hansen@intel.com designates 134.134.136.100 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 orsmga002.jf.intel.com ([10.7.209.21]) by orsmga105.jf.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 31 Jul 2019 09:43:46 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.64,330,1559545200"; d="scan'208";a="183748784" Received: from ray.jf.intel.com (HELO [10.7.201.140]) ([10.7.201.140]) by orsmga002.jf.intel.com with ESMTP; 31 Jul 2019 09:43:46 -0700 Subject: Re: [PATCH v6 1/2] arm64: Define Documentation/arm64/tagged-address-abi.rst To: 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 Cc: Catalin Marinas , Will Deacon , Andrey Konovalov , Szabolcs Nagy References: <20190725135044.24381-1-vincenzo.frascino@arm.com> <20190725135044.24381-2-vincenzo.frascino@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: <20190725135044.24381-2-vincenzo.frascino@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 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?