Re: [PATCH RFC] x86/cpu: fix intermittent lockup on poweroff

[Dave Hansen]

On 4/25/23 12:26, Tony Battersby wrote:
> -	if (cpuid_eax(0x8000001f) & BIT(0))
> +	if (c->extended_cpuid_level >= 0x8000001f &&
> +	    (cpuid_eax(0x8000001f) & BIT(0)))
>  		native_wbinvd();

Oh, so the existing code is running into the

> If a value entered for CPUID.EAX is higher than the maximum input
> value for basic or extended function for that processor then the data
> for the highest basic information leaf is returned
behavior.  It's basically looking at BIT(0) of some random extended
leaf.  Probably 0x80000008 based on your 'cpuid -r' output.