Re: [PATCH v2 1/2] x86/x2apic: Disable x2apic on resume if the kernel expects so

[Sohil Mehta]

On 3/5/2026 9:46 PM, Shashank Balaji wrote:

> So at least as per the spec, re-enablement of x2apic by the firmware is allowed
> if "x2apic on" is a part of the initial boot configuration.
> 

The code changes look fine to me. I am still a bit uncertain about the
"x2apic on" BIOS option. I hope the firmware provides more description
to the user about what it does.

Anyway,

Reviewed-by: Sohil Mehta <sohil.mehta@xxxxxxxxx>


> @@ -2456,6 +2457,15 @@ static void lapic_resume(void *data)
>  	if (x2apic_mode) {
>  		__x2apic_enable();
>  	} else {
> +		/*
> +		 * x2apic may have been re-enabled by the firmware on resuming
> +		 * from s2ram
> +		 */

This comment is mostly unnecessary because the pr_warn conveys the same
message.

> +		if (x2apic_enabled()) {
> +			pr_warn_once("x2apic: re-enabled by firmware during resume. Disabling\n");
> +			__x2apic_disable();
> +		}
> +