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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 1/4] KVM: arm64: Enable Pointer Authentication at EL2 if available
Date: Mon, 15 Jun 2020 11:03:18 +0100	[thread overview]
Message-ID: <20200615100318.GA773@C02TD0UTHF1T.local> (raw)
In-Reply-To: <20200615081954.6233-2-maz@kernel.org>

On Mon, Jun 15, 2020 at 09:19:51AM +0100, Marc Zyngier wrote:
> While initializing EL2, switch Pointer Authentication if detected
> from EL1. We use the EL1-provided keys though.

Perhaps "enable address authentication", to avoid confusion with
context-switch, and since generic authentication cannot be disabled
locally at EL2.

> 
> Signed-off-by: Marc Zyngier <maz@kernel.org>
> ---
>  arch/arm64/kvm/hyp-init.S | 11 +++++++++++
>  1 file changed, 11 insertions(+)
> 
> diff --git a/arch/arm64/kvm/hyp-init.S b/arch/arm64/kvm/hyp-init.S
> index 6e6ed5581eed..81732177507d 100644
> --- a/arch/arm64/kvm/hyp-init.S
> +++ b/arch/arm64/kvm/hyp-init.S
> @@ -104,6 +104,17 @@ alternative_else_nop_endif
>  	 */
>  	mov_q	x4, (SCTLR_EL2_RES1 | (SCTLR_ELx_FLAGS & ~SCTLR_ELx_A))
>  CPU_BE(	orr	x4, x4, #SCTLR_ELx_EE)
> +alternative_if ARM64_HAS_ADDRESS_AUTH_ARCH
> +	b	1f
> +alternative_else_nop_endif
> +alternative_if_not ARM64_HAS_ADDRESS_AUTH_IMP_DEF
> +	b	2f
> +alternative_else_nop_endif

I see this is the same pattern we use in the kvm context switch, but I
think we can use the ARM64_HAS_ADDRESS_AUTH cap instead (likewise in the
existing code).

AFAICT that won't permit mismatch given both ARM64_HAS_ADDRESS_AUTH_ARCH
and ARM64_HAS_ADDRESS_AUTH_IMP_DEF are dealt with as
ARM64_CPUCAP_BOOT_CPU_FEATURE.

> +1:
> +	orr	x4, x4, #(SCTLR_ELx_ENIA | SCTLR_ELx_ENIB)
> +	orr	x4, x4, #SCTLR_ELx_ENDA
> +	orr	x4, x4, #SCTLR_ELx_ENDB

Assuming we have a spare register, it would be nice if we could follow the same
pattern as in proc.S, where we do:

| ldr     x2, =SCTLR_ELx_ENIA | SCTLR_ELx_ENIB | \
|              SCTLR_ELx_ENDA | SCTLR_ELx_ENDB
| orr     x0, x0, x2

... though we could/should use mov_q rather than a load literal, here and in
proc.S.

... otherwise this looks sound to me.

Thanks,
Mark.

> +2:
>  	msr	sctlr_el2, x4
>  	isb
>  
> -- 
> 2.27.0
> 
> _______________________________________________
> kvmarm mailing list
> kvmarm@lists.cs.columbia.edu
> https://lists.cs.columbia.edu/mailman/listinfo/kvmarm
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  parent reply	other threads:[~2020-06-15 10:03 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 [this message]
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
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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