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From: Mark Rutland <mark.rutland@arm.com>
To: Marc Zyngier <maz@kernel.org>
Cc: kernel-team@android.com, linux-arm-kernel@lists.infradead.org,
	kvm@vger.kernel.org, kvmarm@lists.cs.columbia.edu
Subject: Re: [PATCH 4/4] KVM: arm64: Check HCR_EL2 instead of shadow copy to swap PtrAuth registers
Date: Mon, 15 Jun 2020 11:25:29 +0100	[thread overview]
Message-ID: <20200615102529.GD773@C02TD0UTHF1T.local> (raw)
In-Reply-To: <20200615081954.6233-5-maz@kernel.org>

On Mon, Jun 15, 2020 at 09:19:54AM +0100, Marc Zyngier wrote:
> When save/restoring PtrAuth registers between host and guest, it is
> pretty useless to fetch the in-memory state, while we have the right
> state in the HCR_EL2 system register. Use that instead.
> 
> Signed-off-by: Marc Zyngier <maz@kernel.org>

It took me a while to spot that we switched the guest/host hcr_el2 value
in the __activate_traps() and __deactivate_traps() paths, but given that
this is only called in the __kvm_vcpu_run_*() paths called between
those, I agree this is sound. Given that:

Acked-by: Mark Rutland <mark.rutland@arm.com>

Mark.

> ---
>  arch/arm64/include/asm/kvm_ptrauth.h | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/arm64/include/asm/kvm_ptrauth.h b/arch/arm64/include/asm/kvm_ptrauth.h
> index 6301813dcace..f1830173fa9e 100644
> --- a/arch/arm64/include/asm/kvm_ptrauth.h
> +++ b/arch/arm64/include/asm/kvm_ptrauth.h
> @@ -74,7 +74,7 @@ alternative_if_not ARM64_HAS_ADDRESS_AUTH_IMP_DEF
>  	b	1001f
>  alternative_else_nop_endif
>  1000:
> -	ldr	\reg1, [\g_ctxt, #(VCPU_HCR_EL2 - VCPU_CONTEXT)]
> +	mrs	\reg1, hcr_el2
>  	and	\reg1, \reg1, #(HCR_API | HCR_APK)
>  	cbz	\reg1, 1001f
>  	add	\reg1, \g_ctxt, #CPU_APIAKEYLO_EL1
> @@ -90,7 +90,7 @@ alternative_if_not ARM64_HAS_ADDRESS_AUTH_IMP_DEF
>  	b	2001f
>  alternative_else_nop_endif
>  2000:
> -	ldr	\reg1, [\g_ctxt, #(VCPU_HCR_EL2 - VCPU_CONTEXT)]
> +	mrs	\reg1, hcr_el2
>  	and	\reg1, \reg1, #(HCR_API | HCR_APK)
>  	cbz	\reg1, 2001f
>  	add	\reg1, \g_ctxt, #CPU_APIAKEYLO_EL1
> -- 
> 2.27.0
> 
> _______________________________________________
> kvmarm mailing list
> kvmarm@lists.cs.columbia.edu
> https://lists.cs.columbia.edu/mailman/listinfo/kvmarm

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  reply	other threads:[~2020-06-15 10:25 UTC|newest]

Thread overview: 17+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-06-15  8:19 [PATCH 0/4] KVM/arm64: Enable PtrAuth on non-VHE KVM Marc Zyngier
2020-06-15  8:19 ` [PATCH 1/4] KVM: arm64: Enable Pointer Authentication at EL2 if available Marc Zyngier
2020-06-15  8:48   ` Andrew Scull
2020-06-15 10:45     ` Marc Zyngier
2020-06-15 10:03   ` Mark Rutland
2020-06-15 10:55     ` Marc Zyngier
2020-06-15  8:19 ` [PATCH 2/4] KVM: arm64: Allow ARM64_PTR_AUTH when ARM64_VHE=n Marc Zyngier
2020-06-15  8:58   ` Andrew Scull
2020-06-15 10:12   ` Mark Rutland
2020-06-15  8:19 ` [PATCH 3/4] KVM: arm64: Allow PtrAuth to be enabled from userspace on non-VHE systems Marc Zyngier
2020-06-15  9:09   ` Andrew Scull
2020-06-15 10:16   ` Mark Rutland
2020-06-15  8:19 ` [PATCH 4/4] KVM: arm64: Check HCR_EL2 instead of shadow copy to swap PtrAuth registers Marc Zyngier
2020-06-15 10:25   ` Mark Rutland [this message]
2020-06-15 12:59 ` [PATCH 0/4] KVM/arm64: Enable PtrAuth on non-VHE KVM Dave Martin
2020-06-15 13:22   ` Marc Zyngier
2020-06-15 14:17     ` Dave Martin

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