From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-7.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS,URIBL_BLOCKED autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 2A3CBC282DA for ; Wed, 17 Apr 2019 15:54:44 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id F0AD920675 for ; Wed, 17 Apr 2019 15:54:43 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1732777AbfDQPym (ORCPT ); Wed, 17 Apr 2019 11:54:42 -0400 Received: from foss.arm.com ([217.140.101.70]:47116 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729940AbfDQPym (ORCPT ); Wed, 17 Apr 2019 11:54:42 -0400 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.72.51.249]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 95FF5A78; Wed, 17 Apr 2019 08:54:41 -0700 (PDT) Received: from [10.1.196.92] (usa-sjc-imap-foss1.foss.arm.com [10.72.51.249]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 6544E3F557; Wed, 17 Apr 2019 08:54:38 -0700 (PDT) Subject: Re: [PATCH v9 1/5] KVM: arm64: Add a vcpu flag to control ptrauth for guest To: Dave Martin Cc: Amit Daniel Kachhap , linux-arm-kernel@lists.infradead.org, Catalin Marinas , Will Deacon , Kristina Martsenko , kvmarm@lists.cs.columbia.edu, Ramana Radhakrishnan , linux-kernel@vger.kernel.org References: <1555039236-10608-1-git-send-email-amit.kachhap@arm.com> <1555039236-10608-2-git-send-email-amit.kachhap@arm.com> <239c5d74-221e-cf8c-2c41-80db016bdc2b@arm.com> <20190417145255.GB3567@e103592.cambridge.arm.com> From: Marc Zyngier Openpgp: preference=signencrypt Autocrypt: addr=marc.zyngier@arm.com; prefer-encrypt=mutual; keydata= mQINBE6Jf0UBEADLCxpix34Ch3kQKA9SNlVQroj9aHAEzzl0+V8jrvT9a9GkK+FjBOIQz4KE g+3p+lqgJH4NfwPm9H5I5e3wa+Scz9wAqWLTT772Rqb6hf6kx0kKd0P2jGv79qXSmwru28vJ t9NNsmIhEYwS5eTfCbsZZDCnR31J6qxozsDHpCGLHlYym/VbC199Uq/pN5gH+5JHZyhyZiNW ozUCjMqC4eNW42nYVKZQfbj/k4W9xFfudFaFEhAf/Vb1r6F05eBP1uopuzNkAN7vqS8XcgQH qXI357YC4ToCbmqLue4HK9+2mtf7MTdHZYGZ939OfTlOGuxFW+bhtPQzsHiW7eNe0ew0+LaL 3wdNzT5abPBscqXWVGsZWCAzBmrZato+Pd2bSCDPLInZV0j+rjt7MWiSxEAEowue3IcZA++7 ifTDIscQdpeKT8hcL+9eHLgoSDH62SlubO/y8bB1hV8JjLW/jQpLnae0oz25h39ij4ijcp8N t5slf5DNRi1NLz5+iaaLg4gaM3ywVK2VEKdBTg+JTg3dfrb3DH7ctTQquyKun9IVY8AsxMc6 lxl4HxrpLX7HgF10685GG5fFla7R1RUnW5svgQhz6YVU33yJjk5lIIrrxKI/wLlhn066mtu1 DoD9TEAjwOmpa6ofV6rHeBPehUwMZEsLqlKfLsl0PpsJwov8TQARAQABtCNNYXJjIFp5bmdp ZXIgPG1hcmMuenluZ2llckBhcm0uY29tPokCOwQTAQIAJQIbAwYLCQgHAwIGFQgCCQoLBBYC AwECHgECF4AFAk6NvYYCGQEACgkQI9DQutE9ekObww/+NcUATWXOcnoPflpYG43GZ0XjQLng LQFjBZL+CJV5+1XMDfz4ATH37cR+8gMO1UwmWPv5tOMKLHhw6uLxGG4upPAm0qxjRA/SE3LC 22kBjWiSMrkQgv5FDcwdhAcj8A+gKgcXBeyXsGBXLjo5UQOGvPTQXcqNXB9A3ZZN9vS6QUYN TXFjnUnzCJd+PVI/4jORz9EUVw1q/+kZgmA8/GhfPH3xNetTGLyJCJcQ86acom2liLZZX4+1 6Hda2x3hxpoQo7pTu+XA2YC4XyUstNDYIsE4F4NVHGi88a3N8yWE+Z7cBI2HjGvpfNxZnmKX 6bws6RQ4LHDPhy0yzWFowJXGTqM/e79c1UeqOVxKGFF3VhJJu1nMlh+5hnW4glXOoy/WmDEM UMbl9KbJUfo+GgIQGMp8mwgW0vK4HrSmevlDeMcrLdfbbFbcZLNeFFBn6KqxFZaTd+LpylIH bOPN6fy1Dxf7UZscogYw5Pt0JscgpciuO3DAZo3eXz6ffj2NrWchnbj+SpPBiH4srfFmHY+Y LBemIIOmSqIsjoSRjNEZeEObkshDVG5NncJzbAQY+V3Q3yo9og/8ZiaulVWDbcpKyUpzt7pv cdnY3baDE8ate/cymFP5jGJK++QCeA6u6JzBp7HnKbngqWa6g8qDSjPXBPCLmmRWbc5j0lvA 6ilrF8m5Ag0ETol/RQEQAM/2pdLYCWmf3rtIiP8Wj5NwyjSL6/UrChXtoX9wlY8a4h3EX6E3 64snIJVMLbyr4bwdmPKULlny7T/R8dx/mCOWu/DztrVNQiXWOTKJnd/2iQblBT+W5W8ep/nS w3qUIckKwKdplQtzSKeE+PJ+GMS+DoNDDkcrVjUnsoCEr0aK3cO6g5hLGu8IBbC1CJYSpple VVb/sADnWF3SfUvJ/l4K8Uk4B4+X90KpA7U9MhvDTCy5mJGaTsFqDLpnqp/yqaT2P7kyMG2E w+eqtVIqwwweZA0S+tuqput5xdNAcsj2PugVx9tlw/LJo39nh8NrMxAhv5aQ+JJ2I8UTiHLX QvoC0Yc/jZX/JRB5r4x4IhK34Mv5TiH/gFfZbwxd287Y1jOaD9lhnke1SX5MXF7eCT3cgyB+ hgSu42w+2xYl3+rzIhQqxXhaP232t/b3ilJO00ZZ19d4KICGcakeiL6ZBtD8TrtkRiewI3v0 o8rUBWtjcDRgg3tWx/PcJvZnw1twbmRdaNvsvnlapD2Y9Js3woRLIjSAGOijwzFXSJyC2HU1 AAuR9uo4/QkeIrQVHIxP7TJZdJ9sGEWdeGPzzPlKLHwIX2HzfbdtPejPSXm5LJ026qdtJHgz BAb3NygZG6BH6EC1NPDQ6O53EXorXS1tsSAgp5ZDSFEBklpRVT3E0NrDABEBAAGJAh8EGAEC AAkFAk6Jf0UCGwwACgkQI9DQutE9ekMLBQ//U+Mt9DtFpzMCIHFPE9nNlsCm75j22lNiw6mX mx3cUA3pl+uRGQr/zQC5inQNtjFUmwGkHqrAw+SmG5gsgnM4pSdYvraWaCWOZCQCx1lpaCOl MotrNcwMJTJLQGc4BjJyOeSH59HQDitKfKMu/yjRhzT8CXhys6R0kYMrEN0tbe1cFOJkxSbV 0GgRTDF4PKyLT+RncoKxQe8lGxuk5614aRpBQa0LPafkirwqkUtxsPnarkPUEfkBlnIhAR8L kmneYLu0AvbWjfJCUH7qfpyS/FRrQCoBq9QIEcf2v1f0AIpA27f9KCEv5MZSHXGCdNcbjKw1 39YxYZhmXaHFKDSZIC29YhQJeXWlfDEDq6nIhvurZy3mSh2OMQgaIoFexPCsBBOclH8QUtMk a3jW/qYyrV+qUq9Wf3SKPrXf7B3xB332jFCETbyZQXqmowV+2b3rJFRWn5hK5B+xwvuxKyGq qDOGjof2dKl2zBIxbFgOclV7wqCVkhxSJi/QaOj2zBqSNPXga5DWtX3ekRnJLa1+ijXxmdjz hApihi08gwvP5G9fNGKQyRETePEtEAWt0b7dOqMzYBYGRVr7uS4uT6WP7fzOwAJC4lU7ZYWZ yVshCa0IvTtp1085RtT3qhh9mobkcZ+7cQOY+Tx2RGXS9WeOh2jZjdoWUv6CevXNQyOUXMM= Organization: ARM Ltd Message-ID: Date: Wed, 17 Apr 2019 16:54:32 +0100 User-Agent: Mozilla/5.0 (X11; Linux aarch64; rv:60.0) Gecko/20100101 Thunderbird/60.6.1 MIME-Version: 1.0 In-Reply-To: <20190417145255.GB3567@e103592.cambridge.arm.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 17/04/2019 15:52, Dave Martin wrote: > On Wed, Apr 17, 2019 at 03:19:11PM +0100, Marc Zyngier wrote: >> On 17/04/2019 14:08, Amit Daniel Kachhap wrote: >>> Hi, >>> >>> On 4/17/19 2:05 PM, Marc Zyngier wrote: >>>> On 12/04/2019 04:20, Amit Daniel Kachhap wrote: >>>>> A per vcpu flag is added to check if pointer authentication is >>>>> enabled for the vcpu or not. This flag may be enabled according to >>>>> the necessary user policies and host capabilities. >>>>> >>>>> This patch also adds a helper to check the flag. >>>>> >>>>> Signed-off-by: Amit Daniel Kachhap >>>>> Cc: Mark Rutland >>>>> Cc: Marc Zyngier >>>>> Cc: Christoffer Dall >>>>> Cc: kvmarm@lists.cs.columbia.edu >>>>> --- >>>>> >>>>> Changes since v8: >>>>> * Added a new per vcpu flag which will store Pointer Authentication enable >>>>> status instead of checking them again. [Dave Martin] >>>>> >>>>> arch/arm64/include/asm/kvm_host.h | 4 ++++ >>>>> 1 file changed, 4 insertions(+) >>>>> >>>>> diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h >>>>> index 9d57cf8..31dbc7c 100644 >>>>> --- a/arch/arm64/include/asm/kvm_host.h >>>>> +++ b/arch/arm64/include/asm/kvm_host.h >>>>> @@ -355,10 +355,14 @@ struct kvm_vcpu_arch { >>>>> #define KVM_ARM64_HOST_SVE_ENABLED (1 << 4) /* SVE enabled for EL0 */ >>>>> #define KVM_ARM64_GUEST_HAS_SVE (1 << 5) /* SVE exposed to guest */ >>>>> #define KVM_ARM64_VCPU_SVE_FINALIZED (1 << 6) /* SVE config completed */ >>>>> +#define KVM_ARM64_GUEST_HAS_PTRAUTH (1 << 7) /* PTRAUTH exposed to guest */ >>>>> >>>>> #define vcpu_has_sve(vcpu) (system_supports_sve() && \ >>>>> ((vcpu)->arch.flags & KVM_ARM64_GUEST_HAS_SVE)) >>>>> >>>>> +#define vcpu_has_ptrauth(vcpu) \ >>>>> + ((vcpu)->arch.flags & KVM_ARM64_GUEST_HAS_PTRAUTH) >>>>> + >>>> >>>> Just as for SVE, please first check that the system has PTRAUTH. >>>> Something like: >>>> >>>> (cpus_have_const_cap(ARM64_HAS_GENERIC_AUTH_ARCH) && \ >>>> ((vcpu)->arch.flags & KVM_ARM64_GUEST_HAS_PTRAUTH)) >>> >>> In the subsequent patches, vcpu->arch.flags is only set to >>> KVM_ARM64_GUEST_HAS_PTRAUTH when all host capability check conditions >>> matches such as system_supports_address_auth(), >>> system_supports_generic_auth() so doing them again is repetitive in my view. >> >> It isn't the setting of the flag I care about, but the check of that >> flag. Checking a flag for a feature that cannot be used on the running >> system should have a zero cost, which isn't the case here. >> >> Granted, the impact should be minimal and it looks like it mostly happen >> on the slow path, but at the very least it would be consistent. So even >> if you don't buy my argument about efficiency, please change it in the >> name of consistency. > > One of the annoyances here is there is no single static key for ptrauth. > > I'm assuming we don't want to check both static keys (for address and > generic auth) on hot paths. They both just branches, so I don't see why not. Of course, for people using a lesser compiler (gcc 4.8 or clang), things will suck. But they got it coming anyway. Thanks, M. > Checking just one of the two possibilities is OK for now, but we need > to comment clearly somewhere that that will break if KVM is changed > later to expose ptrauth to guests when the host doesn't support both > types. > > Cheers > ---Dave > -- Jazz is not dead. It just smells funny... From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-7.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS,URIBL_BLOCKED autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 5F0D1C282DC for ; Wed, 17 Apr 2019 15:54:48 +0000 (UTC) Received: from mm01.cs.columbia.edu (mm01.cs.columbia.edu [128.59.11.253]) by mail.kernel.org (Postfix) with ESMTP id 0965D20835 for ; Wed, 17 Apr 2019 15:54:47 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 0965D20835 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=arm.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=kvmarm-bounces@lists.cs.columbia.edu Received: from localhost (localhost [127.0.0.1]) by mm01.cs.columbia.edu (Postfix) with ESMTP id 8BC4D4A51B; Wed, 17 Apr 2019 11:54:47 -0400 (EDT) X-Virus-Scanned: at lists.cs.columbia.edu Received: from mm01.cs.columbia.edu ([127.0.0.1]) by localhost (mm01.cs.columbia.edu [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id Wn5EauDRamix; Wed, 17 Apr 2019 11:54:45 -0400 (EDT) Received: from mm01.cs.columbia.edu (localhost [127.0.0.1]) by mm01.cs.columbia.edu (Postfix) with ESMTP id 338B24A52F; Wed, 17 Apr 2019 11:54:45 -0400 (EDT) Received: from localhost (localhost [127.0.0.1]) by mm01.cs.columbia.edu (Postfix) with ESMTP id A9EF64A511 for ; Wed, 17 Apr 2019 11:54:43 -0400 (EDT) X-Virus-Scanned: at lists.cs.columbia.edu Received: from mm01.cs.columbia.edu ([127.0.0.1]) by localhost (mm01.cs.columbia.edu [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id S5RS1hVIjpUH for ; Wed, 17 Apr 2019 11:54:42 -0400 (EDT) Received: from foss.arm.com (foss.arm.com [217.140.101.70]) by mm01.cs.columbia.edu (Postfix) with ESMTP id 28E914A4CA for ; Wed, 17 Apr 2019 11:54:42 -0400 (EDT) Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.72.51.249]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 95FF5A78; Wed, 17 Apr 2019 08:54:41 -0700 (PDT) Received: from [10.1.196.92] (usa-sjc-imap-foss1.foss.arm.com [10.72.51.249]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 6544E3F557; Wed, 17 Apr 2019 08:54:38 -0700 (PDT) Subject: Re: [PATCH v9 1/5] KVM: arm64: Add a vcpu flag to control ptrauth for guest To: Dave Martin References: <1555039236-10608-1-git-send-email-amit.kachhap@arm.com> <1555039236-10608-2-git-send-email-amit.kachhap@arm.com> <239c5d74-221e-cf8c-2c41-80db016bdc2b@arm.com> <20190417145255.GB3567@e103592.cambridge.arm.com> From: Marc Zyngier Openpgp: preference=signencrypt Autocrypt: addr=marc.zyngier@arm.com; prefer-encrypt=mutual; keydata= mQINBE6Jf0UBEADLCxpix34Ch3kQKA9SNlVQroj9aHAEzzl0+V8jrvT9a9GkK+FjBOIQz4KE g+3p+lqgJH4NfwPm9H5I5e3wa+Scz9wAqWLTT772Rqb6hf6kx0kKd0P2jGv79qXSmwru28vJ t9NNsmIhEYwS5eTfCbsZZDCnR31J6qxozsDHpCGLHlYym/VbC199Uq/pN5gH+5JHZyhyZiNW ozUCjMqC4eNW42nYVKZQfbj/k4W9xFfudFaFEhAf/Vb1r6F05eBP1uopuzNkAN7vqS8XcgQH qXI357YC4ToCbmqLue4HK9+2mtf7MTdHZYGZ939OfTlOGuxFW+bhtPQzsHiW7eNe0ew0+LaL 3wdNzT5abPBscqXWVGsZWCAzBmrZato+Pd2bSCDPLInZV0j+rjt7MWiSxEAEowue3IcZA++7 ifTDIscQdpeKT8hcL+9eHLgoSDH62SlubO/y8bB1hV8JjLW/jQpLnae0oz25h39ij4ijcp8N t5slf5DNRi1NLz5+iaaLg4gaM3ywVK2VEKdBTg+JTg3dfrb3DH7ctTQquyKun9IVY8AsxMc6 lxl4HxrpLX7HgF10685GG5fFla7R1RUnW5svgQhz6YVU33yJjk5lIIrrxKI/wLlhn066mtu1 DoD9TEAjwOmpa6ofV6rHeBPehUwMZEsLqlKfLsl0PpsJwov8TQARAQABtCNNYXJjIFp5bmdp ZXIgPG1hcmMuenluZ2llckBhcm0uY29tPokCOwQTAQIAJQIbAwYLCQgHAwIGFQgCCQoLBBYC AwECHgECF4AFAk6NvYYCGQEACgkQI9DQutE9ekObww/+NcUATWXOcnoPflpYG43GZ0XjQLng LQFjBZL+CJV5+1XMDfz4ATH37cR+8gMO1UwmWPv5tOMKLHhw6uLxGG4upPAm0qxjRA/SE3LC 22kBjWiSMrkQgv5FDcwdhAcj8A+gKgcXBeyXsGBXLjo5UQOGvPTQXcqNXB9A3ZZN9vS6QUYN TXFjnUnzCJd+PVI/4jORz9EUVw1q/+kZgmA8/GhfPH3xNetTGLyJCJcQ86acom2liLZZX4+1 6Hda2x3hxpoQo7pTu+XA2YC4XyUstNDYIsE4F4NVHGi88a3N8yWE+Z7cBI2HjGvpfNxZnmKX 6bws6RQ4LHDPhy0yzWFowJXGTqM/e79c1UeqOVxKGFF3VhJJu1nMlh+5hnW4glXOoy/WmDEM UMbl9KbJUfo+GgIQGMp8mwgW0vK4HrSmevlDeMcrLdfbbFbcZLNeFFBn6KqxFZaTd+LpylIH bOPN6fy1Dxf7UZscogYw5Pt0JscgpciuO3DAZo3eXz6ffj2NrWchnbj+SpPBiH4srfFmHY+Y LBemIIOmSqIsjoSRjNEZeEObkshDVG5NncJzbAQY+V3Q3yo9og/8ZiaulVWDbcpKyUpzt7pv cdnY3baDE8ate/cymFP5jGJK++QCeA6u6JzBp7HnKbngqWa6g8qDSjPXBPCLmmRWbc5j0lvA 6ilrF8m5Ag0ETol/RQEQAM/2pdLYCWmf3rtIiP8Wj5NwyjSL6/UrChXtoX9wlY8a4h3EX6E3 64snIJVMLbyr4bwdmPKULlny7T/R8dx/mCOWu/DztrVNQiXWOTKJnd/2iQblBT+W5W8ep/nS w3qUIckKwKdplQtzSKeE+PJ+GMS+DoNDDkcrVjUnsoCEr0aK3cO6g5hLGu8IBbC1CJYSpple VVb/sADnWF3SfUvJ/l4K8Uk4B4+X90KpA7U9MhvDTCy5mJGaTsFqDLpnqp/yqaT2P7kyMG2E w+eqtVIqwwweZA0S+tuqput5xdNAcsj2PugVx9tlw/LJo39nh8NrMxAhv5aQ+JJ2I8UTiHLX QvoC0Yc/jZX/JRB5r4x4IhK34Mv5TiH/gFfZbwxd287Y1jOaD9lhnke1SX5MXF7eCT3cgyB+ hgSu42w+2xYl3+rzIhQqxXhaP232t/b3ilJO00ZZ19d4KICGcakeiL6ZBtD8TrtkRiewI3v0 o8rUBWtjcDRgg3tWx/PcJvZnw1twbmRdaNvsvnlapD2Y9Js3woRLIjSAGOijwzFXSJyC2HU1 AAuR9uo4/QkeIrQVHIxP7TJZdJ9sGEWdeGPzzPlKLHwIX2HzfbdtPejPSXm5LJ026qdtJHgz BAb3NygZG6BH6EC1NPDQ6O53EXorXS1tsSAgp5ZDSFEBklpRVT3E0NrDABEBAAGJAh8EGAEC AAkFAk6Jf0UCGwwACgkQI9DQutE9ekMLBQ//U+Mt9DtFpzMCIHFPE9nNlsCm75j22lNiw6mX mx3cUA3pl+uRGQr/zQC5inQNtjFUmwGkHqrAw+SmG5gsgnM4pSdYvraWaCWOZCQCx1lpaCOl MotrNcwMJTJLQGc4BjJyOeSH59HQDitKfKMu/yjRhzT8CXhys6R0kYMrEN0tbe1cFOJkxSbV 0GgRTDF4PKyLT+RncoKxQe8lGxuk5614aRpBQa0LPafkirwqkUtxsPnarkPUEfkBlnIhAR8L kmneYLu0AvbWjfJCUH7qfpyS/FRrQCoBq9QIEcf2v1f0AIpA27f9KCEv5MZSHXGCdNcbjKw1 39YxYZhmXaHFKDSZIC29YhQJeXWlfDEDq6nIhvurZy3mSh2OMQgaIoFexPCsBBOclH8QUtMk a3jW/qYyrV+qUq9Wf3SKPrXf7B3xB332jFCETbyZQXqmowV+2b3rJFRWn5hK5B+xwvuxKyGq qDOGjof2dKl2zBIxbFgOclV7wqCVkhxSJi/QaOj2zBqSNPXga5DWtX3ekRnJLa1+ijXxmdjz hApihi08gwvP5G9fNGKQyRETePEtEAWt0b7dOqMzYBYGRVr7uS4uT6WP7fzOwAJC4lU7ZYWZ yVshCa0IvTtp1085RtT3qhh9mobkcZ+7cQOY+Tx2RGXS9WeOh2jZjdoWUv6CevXNQyOUXMM= Organization: ARM Ltd Message-ID: Date: Wed, 17 Apr 2019 16:54:32 +0100 User-Agent: Mozilla/5.0 (X11; Linux aarch64; rv:60.0) Gecko/20100101 Thunderbird/60.6.1 MIME-Version: 1.0 In-Reply-To: <20190417145255.GB3567@e103592.cambridge.arm.com> Content-Language: en-US Cc: Catalin Marinas , Will Deacon , linux-kernel@vger.kernel.org, Kristina Martsenko , Ramana Radhakrishnan , Amit Daniel Kachhap , kvmarm@lists.cs.columbia.edu, linux-arm-kernel@lists.infradead.org X-BeenThere: kvmarm@lists.cs.columbia.edu X-Mailman-Version: 2.1.14 Precedence: list List-Id: Where KVM/ARM decisions are made List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit Errors-To: kvmarm-bounces@lists.cs.columbia.edu Sender: kvmarm-bounces@lists.cs.columbia.edu Message-ID: <20190417155432.DEnWHvBi2pfclV4R7Bv8h-6TFzp40vA_oCw2ihvPWT0@z> On 17/04/2019 15:52, Dave Martin wrote: > On Wed, Apr 17, 2019 at 03:19:11PM +0100, Marc Zyngier wrote: >> On 17/04/2019 14:08, Amit Daniel Kachhap wrote: >>> Hi, >>> >>> On 4/17/19 2:05 PM, Marc Zyngier wrote: >>>> On 12/04/2019 04:20, Amit Daniel Kachhap wrote: >>>>> A per vcpu flag is added to check if pointer authentication is >>>>> enabled for the vcpu or not. This flag may be enabled according to >>>>> the necessary user policies and host capabilities. >>>>> >>>>> This patch also adds a helper to check the flag. >>>>> >>>>> Signed-off-by: Amit Daniel Kachhap >>>>> Cc: Mark Rutland >>>>> Cc: Marc Zyngier >>>>> Cc: Christoffer Dall >>>>> Cc: kvmarm@lists.cs.columbia.edu >>>>> --- >>>>> >>>>> Changes since v8: >>>>> * Added a new per vcpu flag which will store Pointer Authentication enable >>>>> status instead of checking them again. [Dave Martin] >>>>> >>>>> arch/arm64/include/asm/kvm_host.h | 4 ++++ >>>>> 1 file changed, 4 insertions(+) >>>>> >>>>> diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h >>>>> index 9d57cf8..31dbc7c 100644 >>>>> --- a/arch/arm64/include/asm/kvm_host.h >>>>> +++ b/arch/arm64/include/asm/kvm_host.h >>>>> @@ -355,10 +355,14 @@ struct kvm_vcpu_arch { >>>>> #define KVM_ARM64_HOST_SVE_ENABLED (1 << 4) /* SVE enabled for EL0 */ >>>>> #define KVM_ARM64_GUEST_HAS_SVE (1 << 5) /* SVE exposed to guest */ >>>>> #define KVM_ARM64_VCPU_SVE_FINALIZED (1 << 6) /* SVE config completed */ >>>>> +#define KVM_ARM64_GUEST_HAS_PTRAUTH (1 << 7) /* PTRAUTH exposed to guest */ >>>>> >>>>> #define vcpu_has_sve(vcpu) (system_supports_sve() && \ >>>>> ((vcpu)->arch.flags & KVM_ARM64_GUEST_HAS_SVE)) >>>>> >>>>> +#define vcpu_has_ptrauth(vcpu) \ >>>>> + ((vcpu)->arch.flags & KVM_ARM64_GUEST_HAS_PTRAUTH) >>>>> + >>>> >>>> Just as for SVE, please first check that the system has PTRAUTH. >>>> Something like: >>>> >>>> (cpus_have_const_cap(ARM64_HAS_GENERIC_AUTH_ARCH) && \ >>>> ((vcpu)->arch.flags & KVM_ARM64_GUEST_HAS_PTRAUTH)) >>> >>> In the subsequent patches, vcpu->arch.flags is only set to >>> KVM_ARM64_GUEST_HAS_PTRAUTH when all host capability check conditions >>> matches such as system_supports_address_auth(), >>> system_supports_generic_auth() so doing them again is repetitive in my view. >> >> It isn't the setting of the flag I care about, but the check of that >> flag. Checking a flag for a feature that cannot be used on the running >> system should have a zero cost, which isn't the case here. >> >> Granted, the impact should be minimal and it looks like it mostly happen >> on the slow path, but at the very least it would be consistent. So even >> if you don't buy my argument about efficiency, please change it in the >> name of consistency. > > One of the annoyances here is there is no single static key for ptrauth. > > I'm assuming we don't want to check both static keys (for address and > generic auth) on hot paths. They both just branches, so I don't see why not. Of course, for people using a lesser compiler (gcc 4.8 or clang), things will suck. But they got it coming anyway. Thanks, M. > Checking just one of the two possibilities is OK for now, but we need > to comment clearly somewhere that that will break if KVM is changed > later to expose ptrauth to guests when the host doesn't support both > types. > > Cheers > ---Dave > -- Jazz is not dead. It just smells funny... _______________________________________________ kvmarm mailing list kvmarm@lists.cs.columbia.edu https://lists.cs.columbia.edu/mailman/listinfo/kvmarm From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-7.0 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_PASS,URIBL_BLOCKED autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 87616C282DA for ; Wed, 17 Apr 2019 15:54:52 +0000 (UTC) Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 567D720663 for ; Wed, 17 Apr 2019 15:54:52 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="dF8fHFE1" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 567D720663 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=arm.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20170209; h=Sender: Content-Transfer-Encoding:Content-Type:Cc:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:Date: Message-ID:From:References:To:Subject:Reply-To:Content-ID:Content-Description :Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=e7J283vvg71Yo4+gqfe/UoGKBBCzlanr3GPtCh/xCCs=; b=dF8fHFE1HKLpjd RmpplWScfmUxSJgdfm5HePYqad9MtAb+XgNeMSu3C07r4Sdnh3gt1e7CPGTZKvvqXsSZrwPAktbl9 8ghdqQrvlf7H3MMNrumyvkz8T209bSECSe8nWl5zDtSLYU0RQt+9GkT9WsYOr6iAOiNrgP0X6C7PM 6VpwybILX1fd0iez6aFhyQiFu3jydKdscDsKKxM/o9alGjSoi87oBVZ7ANcM7u4QgLwWMEcEltGzV qpfOEJpKpgUVod2/4GmBPCIA1aJj4oNHXw5RX1dS8bIotUhjgLHX/sxaSd3jjKA2VkTnRYZSWaFED b2UnV6+e53gxHPtbhiUg==; Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.90_1 #2 (Red Hat Linux)) id 1hGmtb-0003fh-8z; Wed, 17 Apr 2019 15:54:47 +0000 Received: from foss.arm.com ([217.140.101.70]) by bombadil.infradead.org with esmtp (Exim 4.90_1 #2 (Red Hat Linux)) id 1hGmtY-0003ey-AX for linux-arm-kernel@lists.infradead.org; Wed, 17 Apr 2019 15:54:45 +0000 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.72.51.249]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 95FF5A78; Wed, 17 Apr 2019 08:54:41 -0700 (PDT) Received: from [10.1.196.92] (usa-sjc-imap-foss1.foss.arm.com [10.72.51.249]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 6544E3F557; Wed, 17 Apr 2019 08:54:38 -0700 (PDT) Subject: Re: [PATCH v9 1/5] KVM: arm64: Add a vcpu flag to control ptrauth for guest To: Dave Martin References: <1555039236-10608-1-git-send-email-amit.kachhap@arm.com> <1555039236-10608-2-git-send-email-amit.kachhap@arm.com> <239c5d74-221e-cf8c-2c41-80db016bdc2b@arm.com> <20190417145255.GB3567@e103592.cambridge.arm.com> From: Marc Zyngier Openpgp: preference=signencrypt Autocrypt: addr=marc.zyngier@arm.com; prefer-encrypt=mutual; keydata= mQINBE6Jf0UBEADLCxpix34Ch3kQKA9SNlVQroj9aHAEzzl0+V8jrvT9a9GkK+FjBOIQz4KE g+3p+lqgJH4NfwPm9H5I5e3wa+Scz9wAqWLTT772Rqb6hf6kx0kKd0P2jGv79qXSmwru28vJ t9NNsmIhEYwS5eTfCbsZZDCnR31J6qxozsDHpCGLHlYym/VbC199Uq/pN5gH+5JHZyhyZiNW ozUCjMqC4eNW42nYVKZQfbj/k4W9xFfudFaFEhAf/Vb1r6F05eBP1uopuzNkAN7vqS8XcgQH qXI357YC4ToCbmqLue4HK9+2mtf7MTdHZYGZ939OfTlOGuxFW+bhtPQzsHiW7eNe0ew0+LaL 3wdNzT5abPBscqXWVGsZWCAzBmrZato+Pd2bSCDPLInZV0j+rjt7MWiSxEAEowue3IcZA++7 ifTDIscQdpeKT8hcL+9eHLgoSDH62SlubO/y8bB1hV8JjLW/jQpLnae0oz25h39ij4ijcp8N t5slf5DNRi1NLz5+iaaLg4gaM3ywVK2VEKdBTg+JTg3dfrb3DH7ctTQquyKun9IVY8AsxMc6 lxl4HxrpLX7HgF10685GG5fFla7R1RUnW5svgQhz6YVU33yJjk5lIIrrxKI/wLlhn066mtu1 DoD9TEAjwOmpa6ofV6rHeBPehUwMZEsLqlKfLsl0PpsJwov8TQARAQABtCNNYXJjIFp5bmdp ZXIgPG1hcmMuenluZ2llckBhcm0uY29tPokCOwQTAQIAJQIbAwYLCQgHAwIGFQgCCQoLBBYC AwECHgECF4AFAk6NvYYCGQEACgkQI9DQutE9ekObww/+NcUATWXOcnoPflpYG43GZ0XjQLng LQFjBZL+CJV5+1XMDfz4ATH37cR+8gMO1UwmWPv5tOMKLHhw6uLxGG4upPAm0qxjRA/SE3LC 22kBjWiSMrkQgv5FDcwdhAcj8A+gKgcXBeyXsGBXLjo5UQOGvPTQXcqNXB9A3ZZN9vS6QUYN TXFjnUnzCJd+PVI/4jORz9EUVw1q/+kZgmA8/GhfPH3xNetTGLyJCJcQ86acom2liLZZX4+1 6Hda2x3hxpoQo7pTu+XA2YC4XyUstNDYIsE4F4NVHGi88a3N8yWE+Z7cBI2HjGvpfNxZnmKX 6bws6RQ4LHDPhy0yzWFowJXGTqM/e79c1UeqOVxKGFF3VhJJu1nMlh+5hnW4glXOoy/WmDEM UMbl9KbJUfo+GgIQGMp8mwgW0vK4HrSmevlDeMcrLdfbbFbcZLNeFFBn6KqxFZaTd+LpylIH bOPN6fy1Dxf7UZscogYw5Pt0JscgpciuO3DAZo3eXz6ffj2NrWchnbj+SpPBiH4srfFmHY+Y LBemIIOmSqIsjoSRjNEZeEObkshDVG5NncJzbAQY+V3Q3yo9og/8ZiaulVWDbcpKyUpzt7pv cdnY3baDE8ate/cymFP5jGJK++QCeA6u6JzBp7HnKbngqWa6g8qDSjPXBPCLmmRWbc5j0lvA 6ilrF8m5Ag0ETol/RQEQAM/2pdLYCWmf3rtIiP8Wj5NwyjSL6/UrChXtoX9wlY8a4h3EX6E3 64snIJVMLbyr4bwdmPKULlny7T/R8dx/mCOWu/DztrVNQiXWOTKJnd/2iQblBT+W5W8ep/nS w3qUIckKwKdplQtzSKeE+PJ+GMS+DoNDDkcrVjUnsoCEr0aK3cO6g5hLGu8IBbC1CJYSpple VVb/sADnWF3SfUvJ/l4K8Uk4B4+X90KpA7U9MhvDTCy5mJGaTsFqDLpnqp/yqaT2P7kyMG2E w+eqtVIqwwweZA0S+tuqput5xdNAcsj2PugVx9tlw/LJo39nh8NrMxAhv5aQ+JJ2I8UTiHLX QvoC0Yc/jZX/JRB5r4x4IhK34Mv5TiH/gFfZbwxd287Y1jOaD9lhnke1SX5MXF7eCT3cgyB+ hgSu42w+2xYl3+rzIhQqxXhaP232t/b3ilJO00ZZ19d4KICGcakeiL6ZBtD8TrtkRiewI3v0 o8rUBWtjcDRgg3tWx/PcJvZnw1twbmRdaNvsvnlapD2Y9Js3woRLIjSAGOijwzFXSJyC2HU1 AAuR9uo4/QkeIrQVHIxP7TJZdJ9sGEWdeGPzzPlKLHwIX2HzfbdtPejPSXm5LJ026qdtJHgz BAb3NygZG6BH6EC1NPDQ6O53EXorXS1tsSAgp5ZDSFEBklpRVT3E0NrDABEBAAGJAh8EGAEC AAkFAk6Jf0UCGwwACgkQI9DQutE9ekMLBQ//U+Mt9DtFpzMCIHFPE9nNlsCm75j22lNiw6mX mx3cUA3pl+uRGQr/zQC5inQNtjFUmwGkHqrAw+SmG5gsgnM4pSdYvraWaCWOZCQCx1lpaCOl MotrNcwMJTJLQGc4BjJyOeSH59HQDitKfKMu/yjRhzT8CXhys6R0kYMrEN0tbe1cFOJkxSbV 0GgRTDF4PKyLT+RncoKxQe8lGxuk5614aRpBQa0LPafkirwqkUtxsPnarkPUEfkBlnIhAR8L kmneYLu0AvbWjfJCUH7qfpyS/FRrQCoBq9QIEcf2v1f0AIpA27f9KCEv5MZSHXGCdNcbjKw1 39YxYZhmXaHFKDSZIC29YhQJeXWlfDEDq6nIhvurZy3mSh2OMQgaIoFexPCsBBOclH8QUtMk a3jW/qYyrV+qUq9Wf3SKPrXf7B3xB332jFCETbyZQXqmowV+2b3rJFRWn5hK5B+xwvuxKyGq qDOGjof2dKl2zBIxbFgOclV7wqCVkhxSJi/QaOj2zBqSNPXga5DWtX3ekRnJLa1+ijXxmdjz hApihi08gwvP5G9fNGKQyRETePEtEAWt0b7dOqMzYBYGRVr7uS4uT6WP7fzOwAJC4lU7ZYWZ yVshCa0IvTtp1085RtT3qhh9mobkcZ+7cQOY+Tx2RGXS9WeOh2jZjdoWUv6CevXNQyOUXMM= Organization: ARM Ltd Message-ID: Date: Wed, 17 Apr 2019 16:54:32 +0100 User-Agent: Mozilla/5.0 (X11; Linux aarch64; rv:60.0) Gecko/20100101 Thunderbird/60.6.1 MIME-Version: 1.0 In-Reply-To: <20190417145255.GB3567@e103592.cambridge.arm.com> Content-Language: en-US X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20190417_085444_379303_C2D3AF57 X-CRM114-Status: GOOD ( 22.84 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Catalin Marinas , Will Deacon , linux-kernel@vger.kernel.org, Kristina Martsenko , Ramana Radhakrishnan , Amit Daniel Kachhap , kvmarm@lists.cs.columbia.edu, linux-arm-kernel@lists.infradead.org Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org On 17/04/2019 15:52, Dave Martin wrote: > On Wed, Apr 17, 2019 at 03:19:11PM +0100, Marc Zyngier wrote: >> On 17/04/2019 14:08, Amit Daniel Kachhap wrote: >>> Hi, >>> >>> On 4/17/19 2:05 PM, Marc Zyngier wrote: >>>> On 12/04/2019 04:20, Amit Daniel Kachhap wrote: >>>>> A per vcpu flag is added to check if pointer authentication is >>>>> enabled for the vcpu or not. This flag may be enabled according to >>>>> the necessary user policies and host capabilities. >>>>> >>>>> This patch also adds a helper to check the flag. >>>>> >>>>> Signed-off-by: Amit Daniel Kachhap >>>>> Cc: Mark Rutland >>>>> Cc: Marc Zyngier >>>>> Cc: Christoffer Dall >>>>> Cc: kvmarm@lists.cs.columbia.edu >>>>> --- >>>>> >>>>> Changes since v8: >>>>> * Added a new per vcpu flag which will store Pointer Authentication enable >>>>> status instead of checking them again. [Dave Martin] >>>>> >>>>> arch/arm64/include/asm/kvm_host.h | 4 ++++ >>>>> 1 file changed, 4 insertions(+) >>>>> >>>>> diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h >>>>> index 9d57cf8..31dbc7c 100644 >>>>> --- a/arch/arm64/include/asm/kvm_host.h >>>>> +++ b/arch/arm64/include/asm/kvm_host.h >>>>> @@ -355,10 +355,14 @@ struct kvm_vcpu_arch { >>>>> #define KVM_ARM64_HOST_SVE_ENABLED (1 << 4) /* SVE enabled for EL0 */ >>>>> #define KVM_ARM64_GUEST_HAS_SVE (1 << 5) /* SVE exposed to guest */ >>>>> #define KVM_ARM64_VCPU_SVE_FINALIZED (1 << 6) /* SVE config completed */ >>>>> +#define KVM_ARM64_GUEST_HAS_PTRAUTH (1 << 7) /* PTRAUTH exposed to guest */ >>>>> >>>>> #define vcpu_has_sve(vcpu) (system_supports_sve() && \ >>>>> ((vcpu)->arch.flags & KVM_ARM64_GUEST_HAS_SVE)) >>>>> >>>>> +#define vcpu_has_ptrauth(vcpu) \ >>>>> + ((vcpu)->arch.flags & KVM_ARM64_GUEST_HAS_PTRAUTH) >>>>> + >>>> >>>> Just as for SVE, please first check that the system has PTRAUTH. >>>> Something like: >>>> >>>> (cpus_have_const_cap(ARM64_HAS_GENERIC_AUTH_ARCH) && \ >>>> ((vcpu)->arch.flags & KVM_ARM64_GUEST_HAS_PTRAUTH)) >>> >>> In the subsequent patches, vcpu->arch.flags is only set to >>> KVM_ARM64_GUEST_HAS_PTRAUTH when all host capability check conditions >>> matches such as system_supports_address_auth(), >>> system_supports_generic_auth() so doing them again is repetitive in my view. >> >> It isn't the setting of the flag I care about, but the check of that >> flag. Checking a flag for a feature that cannot be used on the running >> system should have a zero cost, which isn't the case here. >> >> Granted, the impact should be minimal and it looks like it mostly happen >> on the slow path, but at the very least it would be consistent. So even >> if you don't buy my argument about efficiency, please change it in the >> name of consistency. > > One of the annoyances here is there is no single static key for ptrauth. > > I'm assuming we don't want to check both static keys (for address and > generic auth) on hot paths. They both just branches, so I don't see why not. Of course, for people using a lesser compiler (gcc 4.8 or clang), things will suck. But they got it coming anyway. Thanks, M. > Checking just one of the two possibilities is OK for now, but we need > to comment clearly somewhere that that will break if KVM is changed > later to expose ptrauth to guests when the host doesn't support both > types. > > Cheers > ---Dave > -- Jazz is not dead. It just smells funny... _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel