linux-kernel - Re: [PATCH 0/2] KVM: x86: Propagate AMD-specific IBRS bits to guests

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Date:   Mon, 6 Mar 2023 22:44:19 +0100
From:   Borislav Petkov <bp@...en8.de>
To:     Sean Christopherson <seanjc@...gle.com>
Cc:     Takahiro Itazuri <itazur@...zon.com>, dave.hansen@...ux.intel.com,
        kvm@...r.kernel.org, linux-kernel@...r.kernel.org,
        mingo@...hat.com, pbonzini@...hat.com, tglx@...utronix.de,
        x86@...nel.org, zulinx86@...il.com
Subject: Re: [PATCH 0/2] KVM: x86: Propagate AMD-specific IBRS bits to guests

On Mon, Mar 06, 2023 at 01:16:25PM -0800, Sean Christopherson wrote:
> I thought that the consensus was that adding unused-by-the-kernel flags to
> cpufeatures.h is ok so long as the feature is hidden from /proc/cpuinfo and the
> kernel already dedicates a word to the CPUID leaf?

I guess we should finally write it down in Documentation/x86/cpuinfo.rst

And in case there's no dedicated word, it should be resorted to KVM-only
feature flags.

In any case, I'd like for baremetal CPUID stuff to be decoupled from
KVM's machinery as far as possible as both have different goals wrt
feature flags.

Thx.

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette