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 5A0A1C10F12 for ; Wed, 17 Apr 2019 09:39:12 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 3304E2073F for ; Wed, 17 Apr 2019 09:39:12 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731626AbfDQJjK (ORCPT ); Wed, 17 Apr 2019 05:39:10 -0400 Received: from foss.arm.com ([217.140.101.70]:41566 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726237AbfDQJjK (ORCPT ); Wed, 17 Apr 2019 05:39:10 -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 0885A374; Wed, 17 Apr 2019 02:39:08 -0700 (PDT) Received: from [10.162.0.144] (a075553-lin.blr.arm.com [10.162.0.144]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 724023F68F; Wed, 17 Apr 2019 02:39:05 -0700 (PDT) Subject: Re: [PATCH v9 4/5] KVM: arm64: Add capability to advertise ptrauth for guest To: Dave Martin Cc: linux-arm-kernel@lists.infradead.org, Marc Zyngier , 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> <1555039236-10608-5-git-send-email-amit.kachhap@arm.com> <20190416163212.GX3567@e103592.cambridge.arm.com> From: Amit Daniel Kachhap Message-ID: <0070b1c2-07d6-7472-1bbc-c252710f6ca3@arm.com> Date: Wed, 17 Apr 2019 15:09:02 +0530 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.4.0 MIME-Version: 1.0 In-Reply-To: <20190416163212.GX3567@e103592.cambridge.arm.com> Content-Type: text/plain; charset=utf-8; format=flowed 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 Hi, On 4/16/19 10:02 PM, Dave Martin wrote: > On Fri, Apr 12, 2019 at 08:50:35AM +0530, Amit Daniel Kachhap wrote: >> This patch advertises the capability of two cpu feature called address >> pointer authentication and generic pointer authentication. These >> capabilities depend upon system support for pointer authentication and >> VHE mode. >> >> The current arm64 KVM partially implements pointer authentication and >> support of address/generic authentication are tied together. However, >> separate ABI requirements for both of them is added so that any future >> isolated implementation will not require any ABI changes. >> >> Signed-off-by: Amit Daniel Kachhap >> Cc: Mark Rutland >> Cc: Marc Zyngier >> Cc: Christoffer Dall >> Cc: kvmarm@lists.cs.columbia.edu >> --- >> Changes since v8: >> * Keep the capability check same for the 2 vcpu ptrauth features. [Dave Martin] >> >> Documentation/virtual/kvm/api.txt | 2 ++ >> arch/arm64/kvm/reset.c | 5 +++++ >> include/uapi/linux/kvm.h | 2 ++ >> 3 files changed, 9 insertions(+) >> >> diff --git a/Documentation/virtual/kvm/api.txt b/Documentation/virtual/kvm/api.txt >> index 9d202f4..56021d0 100644 >> --- a/Documentation/virtual/kvm/api.txt >> +++ b/Documentation/virtual/kvm/api.txt >> @@ -2756,9 +2756,11 @@ Possible features: >> - KVM_ARM_VCPU_PTRAUTH_ADDRESS: Enables Address Pointer authentication >> for the CPU and supported only on arm64 architecture. >> Must be requested if KVM_ARM_VCPU_PTRAUTH_GENERIC is also requested. >> + Depends on KVM_CAP_ARM_PTRAUTH_ADDRESS. > > What if KVM_CAP_ARM_PTRAUTH_ADDRESS is absent and > KVM_ARM_VCPU_PTRAUTH_GENERIC is requested? By these rules, we have a > contradiction: userspace both must request and must not request > KVM_ARM_VCPU_PTRAUTH_ADDRESS. > > We could qualify as follows: > > Depends on KVM_CAP_ARM_PTRAUTH_ADDRESS. > Must be requested if KVM_CAP_ARM_PTRAUTH_ADDRESS is present and > KVM_ARM_VCPU_PTRAUTH_GENERIC is also requested. ok agree. This makes it clear. > >> - KVM_ARM_VCPU_PTRAUTH_GENERIC: Enables Generic Pointer authentication >> for the CPU and supported only on arm64 architecture. >> Must be requested if KVM_ARM_VCPU_PTRAUTH_ADDRESS is also requested. >> + Depends on KVM_CAP_ARM_PTRAUTH_GENERIC. > > Similarly. > > Or, we go back to having a single cap and a single feature, and add > more caps/features later on if we decide it's possible to support > address/generic auth separately later on. > > Otherwise, we end up with complex rules that can't be tested. This is a > high price to pay for forwards compatibility: userspace's conformance to > the rules can't be fully tested, so there's a fair chance it won't work > properly anyway when hardware/KVM with just one auth type appears. > > [...] > > Thoughts? I agree that single cpufeature/capability is a simple solution to implement. The bifurcation of feature was done to reflect the different ID register split up. But the h/w implementation provides a same EL2 exception trap for both the features and hence current implementation ties both of the features together. I guess in future if this is limitation goes away then one auth type is possible. Here I am not sure if the future h/w will retain this merged exception trap and add 2 new separate exception trap in addition to it. I guess it will be probably simple split-up of this merged exception trap. In this case there won't be any ABI change required as per current implementation. Thanks, Amit Daniel > > Cheers > ---Dave > 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 D315FC282DA for ; Wed, 17 Apr 2019 09:39:13 +0000 (UTC) Received: from mm01.cs.columbia.edu (mm01.cs.columbia.edu [128.59.11.253]) by mail.kernel.org (Postfix) with ESMTP id 6D6CC2073F for ; Wed, 17 Apr 2019 09:39:13 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 6D6CC2073F 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 D7FDD4A4C6; Wed, 17 Apr 2019 05:39:12 -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 5pzzs2eOrIgn; Wed, 17 Apr 2019 05:39:11 -0400 (EDT) Received: from mm01.cs.columbia.edu (localhost [127.0.0.1]) by mm01.cs.columbia.edu (Postfix) with ESMTP id 75EFD4A4F3; Wed, 17 Apr 2019 05:39:11 -0400 (EDT) Received: from localhost (localhost [127.0.0.1]) by mm01.cs.columbia.edu (Postfix) with ESMTP id 39E404A4F3 for ; Wed, 17 Apr 2019 05:39:10 -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 FZSMuBzGDVp1 for ; Wed, 17 Apr 2019 05:39:08 -0400 (EDT) Received: from foss.arm.com (foss.arm.com [217.140.101.70]) by mm01.cs.columbia.edu (Postfix) with ESMTP id B53AA4A4C6 for ; Wed, 17 Apr 2019 05:39:08 -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 0885A374; Wed, 17 Apr 2019 02:39:08 -0700 (PDT) Received: from [10.162.0.144] (a075553-lin.blr.arm.com [10.162.0.144]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 724023F68F; Wed, 17 Apr 2019 02:39:05 -0700 (PDT) Subject: Re: [PATCH v9 4/5] KVM: arm64: Add capability to advertise ptrauth for guest To: Dave Martin References: <1555039236-10608-1-git-send-email-amit.kachhap@arm.com> <1555039236-10608-5-git-send-email-amit.kachhap@arm.com> <20190416163212.GX3567@e103592.cambridge.arm.com> From: Amit Daniel Kachhap Message-ID: <0070b1c2-07d6-7472-1bbc-c252710f6ca3@arm.com> Date: Wed, 17 Apr 2019 15:09:02 +0530 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.4.0 MIME-Version: 1.0 In-Reply-To: <20190416163212.GX3567@e103592.cambridge.arm.com> Content-Language: en-US Cc: Marc Zyngier , Catalin Marinas , Will Deacon , linux-kernel@vger.kernel.org, Kristina Martsenko , Ramana Radhakrishnan , 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-Transfer-Encoding: 7bit Content-Type: text/plain; charset="UTF-8"; format="flowed" Errors-To: kvmarm-bounces@lists.cs.columbia.edu Sender: kvmarm-bounces@lists.cs.columbia.edu Message-ID: <20190417093902.8FSM8TxurvepkaljHA7-OSBJQm7gvHq4B00_B_mWQbI@z> Hi, On 4/16/19 10:02 PM, Dave Martin wrote: > On Fri, Apr 12, 2019 at 08:50:35AM +0530, Amit Daniel Kachhap wrote: >> This patch advertises the capability of two cpu feature called address >> pointer authentication and generic pointer authentication. These >> capabilities depend upon system support for pointer authentication and >> VHE mode. >> >> The current arm64 KVM partially implements pointer authentication and >> support of address/generic authentication are tied together. However, >> separate ABI requirements for both of them is added so that any future >> isolated implementation will not require any ABI changes. >> >> Signed-off-by: Amit Daniel Kachhap >> Cc: Mark Rutland >> Cc: Marc Zyngier >> Cc: Christoffer Dall >> Cc: kvmarm@lists.cs.columbia.edu >> --- >> Changes since v8: >> * Keep the capability check same for the 2 vcpu ptrauth features. [Dave Martin] >> >> Documentation/virtual/kvm/api.txt | 2 ++ >> arch/arm64/kvm/reset.c | 5 +++++ >> include/uapi/linux/kvm.h | 2 ++ >> 3 files changed, 9 insertions(+) >> >> diff --git a/Documentation/virtual/kvm/api.txt b/Documentation/virtual/kvm/api.txt >> index 9d202f4..56021d0 100644 >> --- a/Documentation/virtual/kvm/api.txt >> +++ b/Documentation/virtual/kvm/api.txt >> @@ -2756,9 +2756,11 @@ Possible features: >> - KVM_ARM_VCPU_PTRAUTH_ADDRESS: Enables Address Pointer authentication >> for the CPU and supported only on arm64 architecture. >> Must be requested if KVM_ARM_VCPU_PTRAUTH_GENERIC is also requested. >> + Depends on KVM_CAP_ARM_PTRAUTH_ADDRESS. > > What if KVM_CAP_ARM_PTRAUTH_ADDRESS is absent and > KVM_ARM_VCPU_PTRAUTH_GENERIC is requested? By these rules, we have a > contradiction: userspace both must request and must not request > KVM_ARM_VCPU_PTRAUTH_ADDRESS. > > We could qualify as follows: > > Depends on KVM_CAP_ARM_PTRAUTH_ADDRESS. > Must be requested if KVM_CAP_ARM_PTRAUTH_ADDRESS is present and > KVM_ARM_VCPU_PTRAUTH_GENERIC is also requested. ok agree. This makes it clear. > >> - KVM_ARM_VCPU_PTRAUTH_GENERIC: Enables Generic Pointer authentication >> for the CPU and supported only on arm64 architecture. >> Must be requested if KVM_ARM_VCPU_PTRAUTH_ADDRESS is also requested. >> + Depends on KVM_CAP_ARM_PTRAUTH_GENERIC. > > Similarly. > > Or, we go back to having a single cap and a single feature, and add > more caps/features later on if we decide it's possible to support > address/generic auth separately later on. > > Otherwise, we end up with complex rules that can't be tested. This is a > high price to pay for forwards compatibility: userspace's conformance to > the rules can't be fully tested, so there's a fair chance it won't work > properly anyway when hardware/KVM with just one auth type appears. > > [...] > > Thoughts? I agree that single cpufeature/capability is a simple solution to implement. The bifurcation of feature was done to reflect the different ID register split up. But the h/w implementation provides a same EL2 exception trap for both the features and hence current implementation ties both of the features together. I guess in future if this is limitation goes away then one auth type is possible. Here I am not sure if the future h/w will retain this merged exception trap and add 2 new separate exception trap in addition to it. I guess it will be probably simple split-up of this merged exception trap. In this case there won't be any ABI change required as per current implementation. Thanks, Amit Daniel > > Cheers > ---Dave > _______________________________________________ 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 40418C10F12 for ; Wed, 17 Apr 2019 09:39:17 +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 0BC092073F for ; Wed, 17 Apr 2019 09:39:16 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="HYIGx8uB" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 0BC092073F 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-Type: Content-Transfer-Encoding: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=2ZQGY0vCa8GyvXMaGuwtpFo45mmuz6W5yAEkp5X//sE=; b=HYIGx8uBB2d48hI69bjnHC6ha Z9ctAps880VY6kaZpHWlETEF6J9hyboHW6yGTFIH3kiNkKHBRmnhBcU7AvGJr+4iYNreY9/98li1D Bh5vxoT6VwR3kwUXeWUhZrIc32+lWSbidw4wPLn5fvt+BU8179vkrIFS2VFozXPwr02KqO09y3F3a RaGnhaUdj0aESbRb1mPGRUQb6lvhhSM97YDvSjH4j/njqa9fPXZKU9qpSx2wgo/e9Mo62yGrgosw4 1n8MFHlYqMb0I+FKKzFo+wgAUaYMp6rwDHCajMvJaJnBtkP5BkpkAfSRIvqVWkvRZt6m7leVjRbxE wZoiCBhBQ==; 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 1hGh27-0003jh-Cr; Wed, 17 Apr 2019 09:39:11 +0000 Received: from usa-sjc-mx-foss1.foss.arm.com ([217.140.101.70] helo=foss.arm.com) by bombadil.infradead.org with esmtp (Exim 4.90_1 #2 (Red Hat Linux)) id 1hGh24-0003jF-SZ for linux-arm-kernel@lists.infradead.org; Wed, 17 Apr 2019 09:39:10 +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 0885A374; Wed, 17 Apr 2019 02:39:08 -0700 (PDT) Received: from [10.162.0.144] (a075553-lin.blr.arm.com [10.162.0.144]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 724023F68F; Wed, 17 Apr 2019 02:39:05 -0700 (PDT) Subject: Re: [PATCH v9 4/5] KVM: arm64: Add capability to advertise ptrauth for guest To: Dave Martin References: <1555039236-10608-1-git-send-email-amit.kachhap@arm.com> <1555039236-10608-5-git-send-email-amit.kachhap@arm.com> <20190416163212.GX3567@e103592.cambridge.arm.com> From: Amit Daniel Kachhap Message-ID: <0070b1c2-07d6-7472-1bbc-c252710f6ca3@arm.com> Date: Wed, 17 Apr 2019 15:09:02 +0530 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.4.0 MIME-Version: 1.0 In-Reply-To: <20190416163212.GX3567@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_023908_936995_B6BD5B7B X-CRM114-Status: GOOD ( 24.19 ) 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: Marc Zyngier , Catalin Marinas , Will Deacon , linux-kernel@vger.kernel.org, Kristina Martsenko , Ramana Radhakrishnan , kvmarm@lists.cs.columbia.edu, linux-arm-kernel@lists.infradead.org Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset="us-ascii"; Format="flowed" Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org Hi, On 4/16/19 10:02 PM, Dave Martin wrote: > On Fri, Apr 12, 2019 at 08:50:35AM +0530, Amit Daniel Kachhap wrote: >> This patch advertises the capability of two cpu feature called address >> pointer authentication and generic pointer authentication. These >> capabilities depend upon system support for pointer authentication and >> VHE mode. >> >> The current arm64 KVM partially implements pointer authentication and >> support of address/generic authentication are tied together. However, >> separate ABI requirements for both of them is added so that any future >> isolated implementation will not require any ABI changes. >> >> Signed-off-by: Amit Daniel Kachhap >> Cc: Mark Rutland >> Cc: Marc Zyngier >> Cc: Christoffer Dall >> Cc: kvmarm@lists.cs.columbia.edu >> --- >> Changes since v8: >> * Keep the capability check same for the 2 vcpu ptrauth features. [Dave Martin] >> >> Documentation/virtual/kvm/api.txt | 2 ++ >> arch/arm64/kvm/reset.c | 5 +++++ >> include/uapi/linux/kvm.h | 2 ++ >> 3 files changed, 9 insertions(+) >> >> diff --git a/Documentation/virtual/kvm/api.txt b/Documentation/virtual/kvm/api.txt >> index 9d202f4..56021d0 100644 >> --- a/Documentation/virtual/kvm/api.txt >> +++ b/Documentation/virtual/kvm/api.txt >> @@ -2756,9 +2756,11 @@ Possible features: >> - KVM_ARM_VCPU_PTRAUTH_ADDRESS: Enables Address Pointer authentication >> for the CPU and supported only on arm64 architecture. >> Must be requested if KVM_ARM_VCPU_PTRAUTH_GENERIC is also requested. >> + Depends on KVM_CAP_ARM_PTRAUTH_ADDRESS. > > What if KVM_CAP_ARM_PTRAUTH_ADDRESS is absent and > KVM_ARM_VCPU_PTRAUTH_GENERIC is requested? By these rules, we have a > contradiction: userspace both must request and must not request > KVM_ARM_VCPU_PTRAUTH_ADDRESS. > > We could qualify as follows: > > Depends on KVM_CAP_ARM_PTRAUTH_ADDRESS. > Must be requested if KVM_CAP_ARM_PTRAUTH_ADDRESS is present and > KVM_ARM_VCPU_PTRAUTH_GENERIC is also requested. ok agree. This makes it clear. > >> - KVM_ARM_VCPU_PTRAUTH_GENERIC: Enables Generic Pointer authentication >> for the CPU and supported only on arm64 architecture. >> Must be requested if KVM_ARM_VCPU_PTRAUTH_ADDRESS is also requested. >> + Depends on KVM_CAP_ARM_PTRAUTH_GENERIC. > > Similarly. > > Or, we go back to having a single cap and a single feature, and add > more caps/features later on if we decide it's possible to support > address/generic auth separately later on. > > Otherwise, we end up with complex rules that can't be tested. This is a > high price to pay for forwards compatibility: userspace's conformance to > the rules can't be fully tested, so there's a fair chance it won't work > properly anyway when hardware/KVM with just one auth type appears. > > [...] > > Thoughts? I agree that single cpufeature/capability is a simple solution to implement. The bifurcation of feature was done to reflect the different ID register split up. But the h/w implementation provides a same EL2 exception trap for both the features and hence current implementation ties both of the features together. I guess in future if this is limitation goes away then one auth type is possible. Here I am not sure if the future h/w will retain this merged exception trap and add 2 new separate exception trap in addition to it. I guess it will be probably simple split-up of this merged exception trap. In this case there won't be any ABI change required as per current implementation. Thanks, Amit Daniel > > Cheers > ---Dave > _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel