linux-kernel - Re: [PATCH v6 2/2] KVM: x86/xen: update Xen CPUID Leaf 4 (tsc info) sub-leaves, if present

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Date:   Wed, 04 Jan 2023 21:03:04 +0000
From:   David Woodhouse <dwmw2@...radead.org>
To:     Sean Christopherson <seanjc@...gle.com>
CC:     Paul Durrant <pdurrant@...zon.com>, x86@...nel.org,
        kvm@...r.kernel.org, linux-kernel@...r.kernel.org,
        Paolo Bonzini <pbonzini@...hat.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        "H. Peter Anvin" <hpa@...or.com>
Subject: Re: [PATCH v6 2/2] KVM: x86/xen: update Xen CPUID Leaf 4 (tsc info) sub-leaves, if present



On 4 January 2023 20:20:55 GMT, Sean Christopherson <seanjc@...gle.com> wrote:
>On Wed, Jan 04, 2023, David Woodhouse wrote:
>> On Wed, 2023-01-04 at 19:40 +0000, Sean Christopherson wrote:
>> > 
>> > arch/x86/include/asm/xen/hypervisor.h also open codes the signature.  Rather than
>> > add a KVM-specific define, what about putting in xen/cpuid.h?  (I've had a version
>> > of this series sitting in my todo pile for far too long, sorry).
>> 
>> xen/cpuid.h is an external header imported from Xen itself so in
>> general I'd prefer to avoid modifying it unless we also send the
>> changes upstream.
>
>*sigh*  Fool me once...
>
>Can we shove it into arch/x86/include/asm/xen/hypervisor.h?  Or is including
>that in KVM too confusing/ugly?

Maybe, if that's our own header. We do include a bunch of stuff intended for use by Xen guests, in arch/x86/kvm/xen.c to provide Xen support. It's only the 32-bit compat bits we define for ourselves within arch/x86/kvm/xen.h.