Re: [PATCH v3 1/3] x86/idle: Disable IBRS when cpu is offline

[Josh Poimboeuf]

On Wed, Jun 21, 2023 at 08:36:01PM -0400, Waiman Long wrote:
> +/*
> + * naitve_play_dead() is essentially a __noreturn function, but it can't
> + * be marked as such as the compiler may complain about it.
> + */

FWIW, we could in theory do so by marking the smp_ops.play_dead function
pointer as __noreturn, but it would be tricky to teach objtool how to
understand that.

>  void native_play_dead(void)
>  {
> +	if (cpu_feature_enabled(X86_FEATURE_KERNEL_IBRS)) {
> +		this_cpu_write(x86_spec_ctrl_current, 0);
> +		native_wrmsrl(MSR_IA32_SPEC_CTRL, 0);
> +	}

Can update_spec_ctrl() be used instead?

-- 
Josh