Re: [PATCH v2 06/17] arm64: Allow EL1 physical timer access when running VHE

[Oliver Upton <oliver.upton@linux.dev>]

Hey Marc,

On Fri, May 26, 2023 at 03:33:37PM +0100, Marc Zyngier wrote:
> To initialise the timer access from EL2 when HCR_EL2.E2H is set,
> we must make use the CNTHCTL_EL2 formap used is appropriate.
> 
> This amounts to shifting the timer/counter enable bits by 10
> to the left.
> 
> Signed-off-by: Marc Zyngier <maz@kernel.org>
> ---
>  arch/arm64/include/asm/el2_setup.h | 5 +++++
>  arch/arm64/kvm/hyp/nvhe/hyp-init.S | 9 +++++++++
>  2 files changed, 14 insertions(+)
> 
> diff --git a/arch/arm64/include/asm/el2_setup.h b/arch/arm64/include/asm/el2_setup.h
> index 037724b19c5c..225bf1f2514d 100644
> --- a/arch/arm64/include/asm/el2_setup.h
> +++ b/arch/arm64/include/asm/el2_setup.h
> @@ -34,6 +34,11 @@
>   */
>  .macro __init_el2_timers
>  	mov	x0, #3				// Enable EL1 physical timers
> +	mrs	x1, hcr_el2
> +	and	x1, x1, #HCR_E2H
> +	cbz	x1, .LnVHE_\@
> +	lsl	x0, x0, #10
> +.LnVHE_\@:
>  	msr	cnthctl_el2, x0
>  	msr	cntvoff_el2, xzr		// Clear virtual offset
>  .endm
> diff --git a/arch/arm64/kvm/hyp/nvhe/hyp-init.S b/arch/arm64/kvm/hyp/nvhe/hyp-init.S
> index a6d67c2bb5ae..f9ee10e29497 100644
> --- a/arch/arm64/kvm/hyp/nvhe/hyp-init.S
> +++ b/arch/arm64/kvm/hyp/nvhe/hyp-init.S
> @@ -95,6 +95,15 @@ SYM_CODE_START_LOCAL(___kvm_hyp_init)
>  	ldr	x1, [x0, #NVHE_INIT_HCR_EL2]
>  	msr	hcr_el2, x1
>  
> +	mov	x2, #HCR_E2H
> +	and	x2, x1, x2
> +	cbz	x2, 1f
> +
> +	mrs	x1, cnthctl_el2
> +	and	x1, x1, #~(BIT(0) | BIT(1))
> +	orr	x1, x1, #(BIT(10) | BIT(11))
> +	msr	cnthctl_el2, x1
> +1:

Can this be done with an alternative block keyed on ARM64_KVM_HVHE?
I get that __init_el2_timers needs to run before the cpu caps have been
evaluated, but I don't think the same applies for ___kvm_hyp_init

-- 
Thanks,
Oliver