Re: [PATCH v6 07/24] arm64: Make PMR part of task context

[Catalin Marinas <catalin.marinas@arm.com>]

On Mon, Nov 12, 2018 at 11:56:58AM +0000, Julien Thierry wrote:
> diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S
> index 039144e..eb8120e 100644
> --- a/arch/arm64/kernel/entry.S
> +++ b/arch/arm64/kernel/entry.S
> @@ -249,6 +249,12 @@ alternative_else_nop_endif
>  	msr	sp_el0, tsk
>  	.endif
>  
> +	/* Save pmr */
> +alternative_if ARM64_HAS_IRQ_PRIO_MASKING
> +	mrs_s	x20, SYS_ICC_PMR_EL1
> +	str	x20, [sp, #S_PMR_SAVE]
> +alternative_else_nop_endif
> +
>  	/*
>  	 * Registers that may be useful after this macro is invoked:
>  	 *
> @@ -269,6 +275,13 @@ alternative_else_nop_endif
>  	/* No need to restore UAO, it will be restored from SPSR_EL1 */
>  	.endif
>  
> +	/* Restore pmr */
> +alternative_if ARM64_HAS_IRQ_PRIO_MASKING
> +	ldr	x20, [sp, #S_PMR_SAVE]
> +	msr_s	SYS_ICC_PMR_EL1, x20
> +	dsb	sy
> +alternative_else_nop_endif

What's this DSB for? If it's needed, please add a comment.

I would have expected an ISB (or none at all as we are going to return
from an exception).

-- 
Catalin