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 07B83C282CE for ; Mon, 8 Apr 2019 08:51:51 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id D6B0120883 for ; Mon, 8 Apr 2019 08:51:50 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726670AbfDHIvt (ORCPT ); Mon, 8 Apr 2019 04:51:49 -0400 Received: from foss.arm.com ([217.140.101.70]:44274 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726497AbfDHIvt (ORCPT ); Mon, 8 Apr 2019 04:51:49 -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 7787215AD; Mon, 8 Apr 2019 01:51:48 -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 375663F718; Mon, 8 Apr 2019 01:51:44 -0700 (PDT) Subject: Re: [PATCH v8 8/9] 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, Mark Rutland References: <1554172037-4516-1-git-send-email-amit.kachhap@arm.com> <1554172037-4516-9-git-send-email-amit.kachhap@arm.com> <20190405110339.GU3567@e103592.cambridge.arm.com> From: Amit Daniel Kachhap Message-ID: Date: Mon, 8 Apr 2019 14:21:42 +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: <20190405110339.GU3567@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 4/5/19 4:33 PM, Dave Martin wrote: > On Tue, Apr 02, 2019 at 07:57:16AM +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 the 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 v7: >> * Created 2 capabilities KVM_CAP_ARM_PTRAUTH_ADDRESS and KVM_CAP_ARM_PTRAUTH_GENERIC >> instead of one KVM_CAP_ARM_PTRAUTH [Kristina Martsenko]. >> * Added documentation here itself instead of in a new patch. >> >> Documentation/virtual/kvm/api.txt | 3 +++ >> arch/arm64/kvm/reset.c | 6 ++++++ >> include/uapi/linux/kvm.h | 2 ++ >> 3 files changed, 11 insertions(+) >> >> diff --git a/Documentation/virtual/kvm/api.txt b/Documentation/virtual/kvm/api.txt >> index aaa048d..9b56892 100644 >> --- a/Documentation/virtual/kvm/api.txt >> +++ b/Documentation/virtual/kvm/api.txt >> @@ -2661,8 +2661,11 @@ Possible features: >> Depends on KVM_CAP_ARM_PMU_V3. >> - KVM_ARM_VCPU_PTRAUTH_ADDRESS: Enables Address Pointer authentication >> for the CPU and supported only on arm64 architecture. >> + Depends on KVM_CAP_ARM_PTRAUTH_ADDRESS. >> - KVM_ARM_VCPU_PTRAUTH_GENERIC: Enables Generic Pointer authentication >> for the CPU and supported only on arm64 architecture. >> + Depends on KVM_CAP_ARM_PTRAUTH_GENERIC. >> >> >> 4.83 KVM_ARM_PREFERRED_TARGET >> diff --git a/arch/arm64/kvm/reset.c b/arch/arm64/kvm/reset.c >> index 717afed..8aa8982 100644 >> --- a/arch/arm64/kvm/reset.c >> +++ b/arch/arm64/kvm/reset.c >> @@ -92,6 +92,12 @@ int kvm_arch_vm_ioctl_check_extension(struct kvm *kvm, long ext) >> case KVM_CAP_ARM_VM_IPA_SIZE: >> r = kvm_ipa_limit; >> break; >> + case KVM_CAP_ARM_PTRAUTH_ADDRESS: >> + r = has_vhe() && system_supports_address_auth(); >> + break; >> + case KVM_CAP_ARM_PTRAUTH_GENERIC: >> + r = has_vhe() && system_supports_generic_auth(); >> + break; > > If some hardware supports just one auth type, we would report just one > of these caps. Although we have the rule that userspace is not allowed > to request these independently in KVM_ARM_VCPU_INIT anyway, I think it > would be easier for userspace if we suppress both caps if either auth > type isn't available on the host. e.g.: > > case KVM_ARM_ARM_PTRAUTH_ADDRESS: > case KVM_ARM_ARM_PTRAUTH_GENERIC: > r = has_vhe() && system_supports_address_auth() && > system_supports_generic_auth(); > > We could revert back to the above code later on, and apply the ABI > relaxations described in my response to the vcpu features patch, if > someday we add support to KVM for coping with host hardware that > supports just one auth type. These 2 different capabilities are introduced in this iteration so I was not clear whether to expose the suppression in capability ioctl level or KVM_ARM_VCPU_INIT ioctl level. But agree that this way will be more clearer to userspace. > > > I'd like Mark to comment on this, since he's more aware of the > architectural situation than I am. ok. Thanks, Amit D. > > Cheers > ---Dave >