linux-kernel - Re: [PATCH v10 21/45] x86/mm: Add support to validate memory when changing C-bit

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Message-ID: <Ygk+HQgeRIwgZ/nt@zn.tnic>
Date:   Sun, 13 Feb 2022 18:21:33 +0100
From:   Borislav Petkov <bp@...en8.de>
To:     Tom Lendacky <thomas.lendacky@....com>
Cc:     Brijesh Singh <brijesh.singh@....com>,
        "Kirill A . Shutemov" <kirill@...temov.name>, 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>,
        "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>,
        Michael Roth <michael.roth@....com>,
        Vlastimil Babka <vbabka@...e.cz>,
        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
Subject: Re: [PATCH v10 21/45] x86/mm: Add support to validate memory when
 changing C-bit

On Sun, Feb 13, 2022 at 08:50:48AM -0600, Tom Lendacky wrote:
> I think there were a lot of assumptions that only SME/SEV would set
> sme_me_mask and that is used, for example, in the cc_platform_has() routine
> to figure out whether we're AMD or Intel. If you go the cc_mask route, I
> think we'll need to add a cc_vendor variable that would then be checked in
> cc_platform_has().

Right, or cc_platform_type or whatever. It would probably be a good
idea to have a variable explicitly state what the active coco flavor is
anyway, as we had some ambiguity questions in the past along the lines
of, what does cc_platform_has() need to return when running as a guest
on the respective platform.

If you have it explicitly, then it would work unambiguously simple. And
then we can get rid of CC_ATTR_GUEST_SEV_SNP or CC_ATTR_GUEST_TDX which
is clumsy.

Thx.

-- 
Regards/Gruss,
    Boris.

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