Re: [PATCH v11 9/9] x86/cpu: Enable LASS by default during CPU initialization

[Dave Hansen]

On 10/29/25 14:03, Sohil Mehta wrote:
...
> +static __always_inline void setup_lass(struct cpuinfo_x86 *c)
> +{
> +	if (cpu_feature_enabled(X86_FEATURE_LASS)) {
> +		/*
> +		 * Legacy vsyscall page access causes a #GP when LASS is
> +		 * active. However, vsyscall emulation isn't supported
> +		 * with #GP. To avoid breaking userspace, disable LASS
> +		 * if the emulation code is compiled in.
> +		 */
> +		if (IS_ENABLED(CONFIG_X86_VSYSCALL_EMULATION)) {
> +			pr_info_once("x86/cpu: Disabling LASS due to CONFIG_X86_VSYSCALL_EMULATION=y\n");
> +			setup_clear_cpu_cap(X86_FEATURE_LASS);
> +			return;
> +		}
> +
> +		cr4_set_bits(X86_CR4_LASS);
> +	}
> +}
This breaks two rules I have:

 1. Indent as little as practical
 2. Keep the main code flow at the lowest indentation level

IOW, this should be.

static __always_inline void setup_lass(struct cpuinfo_x86 *c)
{
	if (!cpu_feature_enabled(X86_FEATURE_LASS))
		return;
...

But I can fix that up when I apply this. I think it's mostly ready.

Reviewed-by: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>