linux-kernel - Re: [PATCH v10 1/5] KVM: arm64: Add a vcpu flag to control ptrauth for guest

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Date:   Wed, 24 Apr 2019 14:42:22 +0100
From:   Dave Martin <Dave.Martin@....com>
To:     Amit Daniel Kachhap <amit.kachhap@....com>
Cc:     Marc Zyngier <marc.zyngier@....com>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will.deacon@....com>,
        linux-kernel@...r.kernel.org,
        Kristina Martsenko <kristina.martsenko@....com>,
        Ramana Radhakrishnan <ramana.radhakrishnan@....com>,
        kvmarm@...ts.cs.columbia.edu, linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH v10 1/5] KVM: arm64: Add a vcpu flag to control ptrauth
 for guest

On Wed, Apr 24, 2019 at 11:27:50AM +0530, Amit Daniel Kachhap wrote:
> Hi,
> 
> On 4/23/19 9:14 PM, Dave Martin wrote:
> >On Tue, Apr 23, 2019 at 10:12:34AM +0530, 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.
> >>
> >>Reviewed-by: Dave Martin <Dave.Martin@....com>
> >>Signed-off-by: Amit Daniel Kachhap <amit.kachhap@....com>
> >>Cc: Mark Rutland <mark.rutland@....com>
> >>Cc: Marc Zyngier <marc.zyngier@....com>
> >>Cc: Christoffer Dall <christoffer.dall@....com>
> >>Cc: kvmarm@...ts.cs.columbia.edu
> >>---
> >>Changes since v9:
> >>
> >>* Added ptrauth cpufeature static check in vcpu_has_ptrauth [Marc Zyngier].
> >>
> >>  arch/arm64/include/asm/kvm_host.h | 5 +++++
> >>  1 file changed, 5 insertions(+)
> >>
> >>diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
> >>index 7a096fd..7ccac42 100644
> >>--- a/arch/arm64/include/asm/kvm_host.h
> >>+++ b/arch/arm64/include/asm/kvm_host.h
> >>@@ -355,10 +355,15 @@ 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)	((system_supports_address_auth() || \
> >>+				  system_supports_generic_auth()) && \
> >
> >Come to think of it, should this be
> >system_supports_address_auth() _&&_ system_supports_generic_auth()?
> I thought about it and kept it this way so that the implementation
> limitation is not introduced in this patch but only in a single place in the
> 3rd patch where all the documentation and reasoning is present on doing this
> way.

OK, I think that's reasonable.  Just wanted to check that I wasn't
missing some subtle issue here.

Cheers
---Dave