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=-8.5 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS,URIBL_BLOCKED, USER_AGENT_MUTT 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 60A9FC10F13 for ; Tue, 16 Apr 2019 16:31:17 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 2C5B0218DA for ; Tue, 16 Apr 2019 16:31:17 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730004AbfDPQbP (ORCPT ); Tue, 16 Apr 2019 12:31:15 -0400 Received: from usa-sjc-mx-foss1.foss.arm.com ([217.140.101.70]:59336 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727928AbfDPQbP (ORCPT ); Tue, 16 Apr 2019 12:31:15 -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 C730880D; Tue, 16 Apr 2019 09:31:14 -0700 (PDT) Received: from e103592.cambridge.arm.com (usa-sjc-imap-foss1.foss.arm.com [10.72.51.249]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 2905E3F59C; Tue, 16 Apr 2019 09:31:13 -0700 (PDT) Date: Tue, 16 Apr 2019 17:31:10 +0100 From: Dave Martin To: Amit Daniel Kachhap 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 Subject: Re: [PATCH v9 3/5] KVM: arm64: Add userspace flag to enable pointer authentication Message-ID: <20190416163110.GW3567@e103592.cambridge.arm.com> References: <1555039236-10608-1-git-send-email-amit.kachhap@arm.com> <1555039236-10608-4-git-send-email-amit.kachhap@arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1555039236-10608-4-git-send-email-amit.kachhap@arm.com> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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. > + 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; > + /* 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, Reviewed-by: Dave Martin Cheers ---Dave