Re: [PATCH 18/22] KVM: SVM: add GMET bit definitions

[Borislav Petkov]

On Mon, Mar 23, 2026 at 08:53:32AM +0100, Paolo Bonzini wrote:
> I am not sure what you mean by ABI in this context, maybe "there are

It means that once we show it in /proc/cpuinfo, we're stuck with it forever
because something in userspace might depend on it.

So we try to avoid that if it can be solved in a different way.

> rules for whether to add stuff to cpuinfo.rst"? If so, GMET matches
> what cpuinfo.rst says:
> 
> * the kernel knows about the feature enough to have an X86_FEATURE bit
> * the kernel supports it and is currently making it available to userspace
> * the hardware supports it.
> 
> The bullet that applies here is the second from the above list: 1)
> this series makes the feature available for userspace and guests to
> use it,

This is the key question: what in userspace is going to parse /proc/cpuinfo
and look for "gmet"?

Because parsing /proc/cpuinfo is the silliest option available but glibc does
it and for some things like, "did the kernel *actually* enable this?" it is
the only way.

If the above applies, can this be solved in a different way? CPUID,
guest_cpu_cap_has(), whatever...

Thx.

-- 
Regards/Gruss,
    Boris.

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