Re: [PATCH] x86/cpu: Add INVLPGB CPU feature flag to /proc/cpuinfo

[Yongting Lin]

On Wed, 18 Mar 2026 10:58:26 -0700, Dave Hansen wrote:
>On 3/18/26 10:52, Yongting Lin wrote:
>> commit 767ae437a32d ("x86/mm: Add INVLPGB feature and Kconfig entry")
>> introduced support for the INVLPGB instruction as a fast TLB
>> invalidation mechanism. However, no corresponding CPU feature flag is
>> exposed via /proc/cpuinfo.
>
>The patch is probably OK, but the changelog is insufficient. Could you
>please read through:
>
>        Documentation/arch/x86/cpuinfo.rst
>
>and use that structure to construct a justification for why this feature
>is needed?

Hi Dave, the invlpgb is a new ISA for newly AMD processors to issue a BROADCAST
operation to invalidate TLB entry in all remote CPUS, avoiding a cost of
IPI tlb flush operations.

It should be visible to Linux user to be aware of this new feature as well
as application programs.

>
>I'd also just appreciate a blurb on why you care. Why did you bother to
send this patch?

Yes, I am back-porting this new feature to an old linux kernel and found
there is no CPU tag in the flags part of /proc/cpuinfo.

Thanks!

Yongting.