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Fri, 19 Oct 2018 04:47:23 -0700 (PDT) Received: from [10.1.196.62] (usa-sjc-imap-foss1.foss.arm.com [10.72.51.249]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 015F93F71D; Fri, 19 Oct 2018 04:47:17 -0700 (PDT) Subject: Re: [PATCH v5 11/17] arm64: docs: document pointer authentication To: Catalin Marinas , Kristina Martsenko Cc: Ramana Radhakrishnan , "linux-arm-kernel@lists.infradead.org" , Mark Rutland , "linux-arch@vger.kernel.org" , Andrew Jones , Jacob Bramley , Arnd Bergmann , Ard Biesheuvel , Adam Wallis , Suzuki Poulose , Will Deacon , Christoffer Dall , "kvmarm@lists.cs.columbia.edu" , Amit Kachhap , Dave P Martin , "linux-kernel@vger.kernel.org" , Kees Cook References: <20181005084754.20950-1-kristina.martsenko@arm.com> <20181005084754.20950-12-kristina.martsenko@arm.com> <9acb0cd2-66b0-1c41-b1a8-7c70608e9a9b@foss.arm.com> <7b0de19b-45b9-f4df-25d1-c7e80fab49dc@arm.com> <20181019113556.ljbdmjo5pdw7muvz@mbp> From: Marc Zyngier Openpgp: preference=signencrypt Autocrypt: addr=marc.zyngier@arm.com; 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Linux aarch64; rv:52.0) Gecko/20100101 Thunderbird/52.9.1 MIME-Version: 1.0 In-Reply-To: <20181019113556.ljbdmjo5pdw7muvz@mbp> Content-Type: text/plain; charset=utf-8 Content-Language: en-GB Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 19/10/18 12:35, Catalin Marinas wrote: > On Tue, Oct 16, 2018 at 05:14:39PM +0100, Kristina Martsenko wrote: >> On 05/10/2018 10:04, Ramana Radhakrishnan wrote: >>> On 05/10/2018 09:47, Kristina Martsenko wrote: [...] >> The other option is to turn off trapping entirely. However then on a >> big.LITTLE system with mismatched pointer authentication support >> instructions will work intermittently on some CPUs but not others. > > That's another case but let's assume we never see such configurations ;). I'd like to put it on the record that I'm not willing to support such a configuration. So my ask is that if we detect a system where only some of the CPUs have pointer authentication support, we either: 1) prevent some of the CPUs from booting (that's harsh) 2) disable KVM (that's easy) I'm perfectly happy with (2). Thanks, M. -- Jazz is not dead. It just smells funny...