Re: [PATCHv6 01/16] x86/cpu: Enumerate the LASS feature bits

Dave Hansen
2025-06-26T17:21:25Z

On 6/26/25 09:07, Borislav Petkov wrote:
>> Makes more sense?
> I meant this crap, ofc:
>
> switch (bug) {
> case X86_BUG_CPU_MELTDOWN:
> if (boot_cpu_has(X86_FEATURE_PTI))
> return sysfs_emit(buf, "Mitigation: PTI\n");
>
> This should say "Mitigation: LASS" if LASS is enabled...
>
> Which begs the question: how do LASS and PTI interact now?

Maybe my babbling about LASS mitigation Meltdown was ill considered. It
seems that I've just muddied the waters.

All the real LASS-capable hardware also has RDCL_NO=1 which is the
_actual_ x86 Meltdown mitigation. Those systems are not vulnerable to
Meltdown in the first place.

They should say: "Not affected" for Meltdown, both before and after LASS.