Re: [PATCH v6] x86/mm: Don't disable INVLPG if "incomplete Global INVLPG flushes" is fixed by microcode or the kernel is running in a hypervisor

[Sean Christopherson]

On Thu, Apr 11, 2024, Xi Ruoyao wrote:
> Per the "Processor Specification Update" documentations referred by the
> intel-microcode-20240312 release note, this microcode release has fixed
> the issue for all affected models.
> 
> So don't disable INVLPG if the microcode is new enough.  The precise
> minimum microcode revision fixing the issue is provided by engineer from
> Intel.
> 
> And the erratum says:
> 
>     This erratum does not apply in VMX non-root operation. It applies
>     only when PCIDs are enabled and either in VMX root operation or
>     outside VMX operation.
> 
> So if the kernel is running in a hypervisor, we are in VMX non-root
> operation and we should be safe.

This should be two separate patches, one to do the precise ucode update check,
and one to keep PCID enabled for guests.