Re: [patch V4 part 1 27/36] arm64: Prepare arch_nmi_enter() for recursion

[Mathieu Desnoyers]

----- On May 5, 2020, at 9:16 AM, Thomas Gleixner tglx@xxxxxxxxxxxxx wrote:

> +#define arch_nmi_enter()						\
[...]							\
> +	___hcr = read_sysreg(hcr_el2);					\
> +	if (!(___hcr & HCR_TGE)) {					\
> +		write_sysreg(___hcr | HCR_TGE, hcr_el2);		\
> +		isb();							\

Why is there an isb() above ^ ....

> +	}								\
> +	/*								\
[...]
> -#define arch_nmi_exit()								\
[...]
> +	/*								\
> +	 * Make sure ___ctx->cnt release is visible before we		\
> +	 * restore the sysreg. Otherwise a new NMI occurring		\
> +	 * right after write_sysreg() can be fooled and think		\
> +	 * we secured things for it.					\
> +	 */								\
> +	barrier();							\
> +	if (!___ctx->cnt && !(___hcr & HCR_TGE))			\
> +		write_sysreg(___hcr, hcr_el2);				\

And not here ?

Thanks,

Mathieu

-- 
Mathieu Desnoyers
EfficiOS Inc.
http://www.efficios.com