[PATCH v3 05/25] arm64: context switch POR_EL0 register

[Mark Brown]

On Fri, Nov 24, 2023 at 04:34:50PM +0000, Joey Gouly wrote:

> +static void flush_poe(void)
> +{
> +	if (system_supports_poe())
> +		write_sysreg_s(POR_EL0_INIT, SYS_POR_EL0);
> +}

Here we have no isb()...

> +static void permission_overlay_switch(struct task_struct *next)
> +{
> +	if (system_supports_poe()) {
> +		current->thread.por_el0 = read_sysreg_s(SYS_POR_EL0);
> +		if (current->thread.por_el0 != next->thread.por_el0) {
> +			write_sysreg_s(next->thread.por_el0, SYS_POR_EL0);
> +			isb();
> +		}
> +	}
> +}

...but here we do, I'd expect them to be consistent.  

If the barrier is needed it'd probably be helpful to have a comment
explaining why we need it before the ERET.
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