linux-kernel - Re: [PATCH Part1 v5 32/38] x86/sev: enable SEV-SNP-validated CPUID in #VC handlers

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Message-ID: <YS5XVBNrASp7Zrig@zn.tnic>
Date:   Tue, 31 Aug 2021 18:22:44 +0200
From:   Borislav Petkov <bp@...en8.de>
To:     Michael Roth <michael.roth@....com>
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>,
        Wanpeng Li <wanpengli@...cent.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>, tony.luck@...el.com,
        marcorr@...gle.com, sathyanarayanan.kuppuswamy@...ux.intel.com
Subject: Re: [PATCH Part1 v5 32/38] x86/sev: enable SEV-SNP-validated CPUID
 in #VC handlers

On Fri, Aug 27, 2021 at 01:32:40PM -0500, Michael Roth wrote:
> If the memory is allocated in boot/compressed/mem_encrypt.S, wouldn't
> kernel proper still need to create a static buffer for its copy?

Just like the other variables like sme_me_mask etc that file allocates
at the bottom. Or do you have a better idea?

> Would that be a reasonable approach for v6?

I don't like the ifdeffery one bit, TBH. I guess you should split it
and have a boot/compressed page and a kernel proper one and keep 'em
separate. That should make everything nice and clean at the cost of 2*4K
which is nothing nowadays.

Thx.

-- 
Regards/Gruss,
    Boris.

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