linux-kernel - Re: [PATCH v9 23/43] KVM: x86: Move lookup of indexed CPUID leafs to helper

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Date:   Thu, 3 Feb 2022 10:44:43 -0600
From:   Michael Roth <michael.roth@....com>
To:     Borislav Petkov <bp@...en8.de>
CC:     Brijesh Singh <brijesh.singh@....com>, <x86@...nel.org>,
        <linux-kernel@...r.kernel.org>, <kvm@...r.kernel.org>,
        <linux-efi@...r.kernel.org>, <platform-driver-x86@...r.kernel.org>,
        <linux-coco@...ts.linux.dev>, <linux-mm@...ck.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Joerg Roedel <jroedel@...e.de>,
        Tom Lendacky <thomas.lendacky@....com>,
        "H. Peter Anvin" <hpa@...or.com>, Ard Biesheuvel <ardb@...nel.org>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Sean Christopherson <seanjc@...gle.com>,
        "Vitaly Kuznetsov" <vkuznets@...hat.com>,
        Jim Mattson <jmattson@...gle.com>,
        "Andy Lutomirski" <luto@...nel.org>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Sergio Lopez <slp@...hat.com>, Peter Gonda <pgonda@...gle.com>,
        "Peter Zijlstra" <peterz@...radead.org>,
        Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>,
        David Rientjes <rientjes@...gle.com>,
        Dov Murik <dovmurik@...ux.ibm.com>,
        Tobin Feldman-Fitzthum <tobin@....com>,
        Vlastimil Babka <vbabka@...e.cz>,
        "Kirill A . Shutemov" <kirill@...temov.name>,
        Andi Kleen <ak@...ux.intel.com>,
        "Dr . David Alan Gilbert" <dgilbert@...hat.com>,
        <brijesh.ksingh@...il.com>, <tony.luck@...el.com>,
        <marcorr@...gle.com>, <sathyanarayanan.kuppuswamy@...ux.intel.com>,
        Venu Busireddy <venu.busireddy@...cle.com>
Subject: Re: [PATCH v9 23/43] KVM: x86: Move lookup of indexed CPUID leafs to
 helper

On Thu, Feb 03, 2022 at 04:16:33PM +0100, Borislav Petkov wrote:
> On Fri, Jan 28, 2022 at 11:17:44AM -0600, Brijesh Singh wrote:
> > From: Michael Roth <michael.roth@....com>
> > 
> > Determining which CPUID leafs have significant ECX/index values is
> > also needed by guest kernel code when doing SEV-SNP-validated CPUID
> > lookups. Move this to common code to keep future updates in sync.
> > 
> > Reviewed-by: Venu Busireddy <venu.busireddy@...cle.com>
> > Signed-off-by: Michael Roth <michael.roth@....com>
> > Signed-off-by: Brijesh Singh <brijesh.singh@....com>
> > ---
> >  arch/x86/include/asm/cpuid.h | 38 ++++++++++++++++++++++++++++++++++++
> >  arch/x86/kvm/cpuid.c         | 19 ++----------------
> >  2 files changed, 40 insertions(+), 17 deletions(-)
> >  create mode 100644 arch/x86/include/asm/cpuid.h
> > 
> > diff --git a/arch/x86/include/asm/cpuid.h b/arch/x86/include/asm/cpuid.h
> > new file mode 100644
> > index 000000000000..00408aded67c
> > --- /dev/null
> > +++ b/arch/x86/include/asm/cpuid.h
> > @@ -0,0 +1,38 @@
> > +/* SPDX-License-Identifier: GPL-2.0 */
> > +/*
> > + * Kernel-based Virtual Machine driver for Linux cpuid support routines
> > + *
> > + * derived from arch/x86/kvm/x86.c
> > + * derived from arch/x86/kvm/cpuid.c
> > + *
> > + * Copyright 2011 Red Hat, Inc. and/or its affiliates.
> > + * Copyright IBM Corporation, 2008
> > + */
> 
> I have no clue what you're trying to achieve by copying the copyright of
> the file this comes from. As dhansen properly points out, those lines
> in that function come from other folks/companies too so why even bother
> with this?

I think Dave's main concern was that I'd added an AMD copyright banner
to a new file that was mostly derived from acpi.c. I thought we had some
agreement on simply adopting the file-wide copyright banner of whatever
source file the new one was derived from, since dropping an existing
copyright seemed similarly in bad taste, but if it's sufficient to lean
on git for getting a more accurate picture of copyright sources then
that sounds good to me and I'll adopt that for the next spin if there
are no objections.

  https://lore.kernel.org/linux-efi/16afaa00-06a9-dc58-6c59-3d1dfb819009@amd.com/T/#m88a765b6090ec794872f73bf0ee6642fd39db947

(In the case of acpi.c it happened to not have a file-wide copyright banner
so things were a little more straightforward for the acpi.c->efi.c movement)

> 
> git history holds the correct and full copyright anyway...
> 
> -- 
> Regards/Gruss,
>     Boris.
> 
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