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 33FEAC10F12 for ; Wed, 17 Apr 2019 08:17:32 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id F15252073F for ; Wed, 17 Apr 2019 08:17:31 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731223AbfDQIRa (ORCPT ); Wed, 17 Apr 2019 04:17:30 -0400 Received: from usa-sjc-mx-foss1.foss.arm.com ([217.140.101.70]:40254 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727013AbfDQIRa (ORCPT ); Wed, 17 Apr 2019 04:17:30 -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 9999CA78; Wed, 17 Apr 2019 01:17:29 -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 1A89B3F690; Wed, 17 Apr 2019 01:17:26 -0700 (PDT) Subject: Re: [PATCH v9 3/5] KVM: arm64: Add userspace flag to enable pointer authentication 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> <1555039236-10608-4-git-send-email-amit.kachhap@arm.com> <20190416163110.GW3567@e103592.cambridge.arm.com> From: Amit Daniel Kachhap Message-ID: Date: Wed, 17 Apr 2019 13:47:24 +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: <20190416163110.GW3567@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 10:01 PM, Dave Martin wrote: > On Fri, Apr 12, 2019 at 08:50:34AM +0530, Amit Daniel Kachhap wrote: >> Now that the building blocks of pointer authentication are present, lets >> add userspace flags KVM_ARM_VCPU_PTRAUTH_ADDRESS and >> KVM_ARM_VCPU_PTRAUTH_GENERIC. These flags will enable pointer >> authentication for the KVM guest on a per-vcpu basis through the ioctl >> KVM_ARM_VCPU_INIT. >> >> This features will allow the KVM guest to allow the handling of >> pointer authentication instructions or to treat them as undefined >> if not set. >> >> Necessary documentations are added to reflect the changes done. >> >> Signed-off-by: Amit Daniel Kachhap >> Cc: Mark Rutland >> Cc: Marc Zyngier >> Cc: Christoffer Dall >> Cc: kvmarm@lists.cs.columbia.edu >> --- >> >> Changes since v8: >> * Update vcpu->arch.flags to final enable state. [Dave Martin] >> * Change in Documentation to make clear the implementation of 2 vcpu >> feature flags. [Dave Martin] >> >> Documentation/arm64/pointer-authentication.txt | 22 ++++++++++++++++++---- >> Documentation/virtual/kvm/api.txt | 6 ++++++ >> arch/arm64/include/asm/kvm_host.h | 2 +- >> arch/arm64/include/uapi/asm/kvm.h | 2 ++ >> arch/arm64/kvm/reset.c | 24 ++++++++++++++++++++++++ >> 5 files changed, 51 insertions(+), 5 deletions(-) >> >> diff --git a/Documentation/arm64/pointer-authentication.txt b/Documentation/arm64/pointer-authentication.txt >> index 5baca42..fc71b33 100644 >> --- a/Documentation/arm64/pointer-authentication.txt >> +++ b/Documentation/arm64/pointer-authentication.txt >> @@ -87,7 +87,21 @@ used to get and set the keys for a thread. >> Virtualization >> -------------- >> >> -Pointer authentication is not currently supported in KVM guests. KVM >> -will mask the feature bits from ID_AA64ISAR1_EL1, and attempted use of >> -the feature will result in an UNDEFINED exception being injected into >> -the guest. >> +Pointer authentication is enabled in KVM guest when each virtual cpu is >> +initialised by passing flags KVM_ARM_VCPU_PTRAUTH_[ADDRESS/GENERIC] and >> +requesting these two separate cpu features to be enabled. The current KVM >> +guest implementation works by enabling both features together, so both >> +these userspace flags are checked before enabling pointer authentication. >> +The separate userspace flag will allow to have no userspace ABI changes >> +if support is added in the future to allow these two features to be >> +enabled independently of one another. >> + >> +As Arm Architecture specifies that Pointer Authentication feature is >> +implemented along with the VHE feature so KVM arm64 ptrauth code relies >> +on VHE mode to be present. >> + >> +Additionally, when these vcpu feature flags are not set then KVM will >> +filter out the Pointer Authentication system key registers from >> +KVM_GET/SET_REG_* ioctls and mask those features from cpufeature ID >> +register. Any attempt to use the Pointer Authentication instructions will >> +result in an UNDEFINED exception being injected into the guest. >> diff --git a/Documentation/virtual/kvm/api.txt b/Documentation/virtual/kvm/api.txt >> index 68509de..9d202f4 100644 >> --- a/Documentation/virtual/kvm/api.txt >> +++ b/Documentation/virtual/kvm/api.txt >> @@ -2753,6 +2753,12 @@ Possible features: >> Depends on KVM_CAP_ARM_PSCI_0_2. >> - KVM_ARM_VCPU_PMU_V3: Emulate PMUv3 for the CPU. >> 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. > > Nit: (arm64 only) would be less verbose. ok. > >> + Must be requested if KVM_ARM_VCPU_PTRAUTH_GENERIC is also requested. >> + - KVM_ARM_VCPU_PTRAUTH_GENERIC: Enables Generic Pointer authentication >> + for the CPU and supported only on arm64 architecture. > > Ditto. (Not a big deal, though.) > >> + Must be requested if KVM_ARM_VCPU_PTRAUTH_ADDRESS is also requested. >> >> - KVM_ARM_VCPU_SVE: Enables SVE for the CPU (arm64 only). >> Depends on KVM_CAP_ARM_SVE. >> diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h >> index a585d82..25f2598 100644 >> --- a/arch/arm64/include/asm/kvm_host.h >> +++ b/arch/arm64/include/asm/kvm_host.h >> @@ -49,7 +49,7 @@ >> >> #define KVM_MAX_VCPUS VGIC_V3_MAX_CPUS >> >> -#define KVM_VCPU_MAX_FEATURES 5 >> +#define KVM_VCPU_MAX_FEATURES 7 >> >> #define KVM_REQ_SLEEP \ >> KVM_ARCH_REQ_FLAGS(0, KVM_REQUEST_WAIT | KVM_REQUEST_NO_WAKEUP) >> diff --git a/arch/arm64/include/uapi/asm/kvm.h b/arch/arm64/include/uapi/asm/kvm.h >> index 6963b7e..fec2253 100644 >> --- a/arch/arm64/include/uapi/asm/kvm.h >> +++ b/arch/arm64/include/uapi/asm/kvm.h >> @@ -103,6 +103,8 @@ struct kvm_regs { >> #define KVM_ARM_VCPU_PSCI_0_2 2 /* CPU uses PSCI v0.2 */ >> #define KVM_ARM_VCPU_PMU_V3 3 /* Support guest PMUv3 */ >> #define KVM_ARM_VCPU_SVE 4 /* enable SVE for this CPU */ >> +#define KVM_ARM_VCPU_PTRAUTH_ADDRESS 5 /* VCPU uses address authentication */ >> +#define KVM_ARM_VCPU_PTRAUTH_GENERIC 6 /* VCPU uses generic authentication */ >> >> struct kvm_vcpu_init { >> __u32 target; >> diff --git a/arch/arm64/kvm/reset.c b/arch/arm64/kvm/reset.c >> index f13378d..d13406b 100644 >> --- a/arch/arm64/kvm/reset.c >> +++ b/arch/arm64/kvm/reset.c >> @@ -221,6 +221,24 @@ static void kvm_vcpu_reset_sve(struct kvm_vcpu *vcpu) >> memset(vcpu->arch.sve_state, 0, vcpu_sve_state_size(vcpu)); >> } >> >> +static int kvm_vcpu_enable_ptrauth(struct kvm_vcpu *vcpu) >> +{ >> + /* Support ptrauth only if the system supports these capabilities. */ >> + if (!has_vhe() || !system_supports_address_auth() || >> + !system_supports_generic_auth()) >> + return -EINVAL; > > Nit: Funny indentation. Please align with the "if (". It's also > preferable to keep the two system_supports_xxx_auth() aligned or on the > same line, since they go together. This might be clearer split up: > > if (!has_vhe()) > return -EINVAL; > > if (!system_supports_address_auth() || > !system_supports_generic_auth()) > return -EINVAL; ok. > >> + /* > > I'd say "for now" here, since we might relax this rule later on. > >> + * Make sure that both address/generic pointer authentication >> + * features are requested by the userspace together. >> + */ >> + if (!test_bit(KVM_ARM_VCPU_PTRAUTH_ADDRESS, vcpu->arch.features) || >> + !test_bit(KVM_ARM_VCPU_PTRAUTH_GENERIC, vcpu->arch.features)) >> + return -EINVAL; >> + >> + vcpu->arch.flags |= KVM_ARM64_GUEST_HAS_PTRAUTH; >> + return 0; >> +} >> + >> /** >> * kvm_reset_vcpu - sets core registers and sys_regs to reset value >> * @vcpu: The VCPU pointer >> @@ -261,6 +279,12 @@ int kvm_reset_vcpu(struct kvm_vcpu *vcpu) >> kvm_vcpu_reset_sve(vcpu); >> } >> >> + if (test_bit(KVM_ARM_VCPU_PTRAUTH_ADDRESS, vcpu->arch.features) || >> + test_bit(KVM_ARM_VCPU_PTRAUTH_GENERIC, vcpu->arch.features)) { > > Nit: funny indentation. > >> + if (kvm_vcpu_enable_ptrauth(vcpu)) >> + goto out; >> + } >> + > > [...] > > With those fixed, sure. > > Reviewed-by: Dave Martin Thanks, Amit > > Cheers > ---Dave >