linux-kernel - Re: [PATCH v9 31/43] x86/compressed/64: Add support for SEV-SNP CPUID table in #VC handlers

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Message-ID: <YgFcXMEvWs9xGTPF@zn.tnic>
Date:   Mon, 7 Feb 2022 18:52:28 +0100
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>,
        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
Subject: Re: [PATCH v9 31/43] x86/compressed/64: Add support for SEV-SNP
 CPUID table in #VC handlers

On Mon, Feb 07, 2022 at 09:37:39AM -0600, Michael Roth wrote:
> Absolutely, I know a thorough review is grueling work, and would never
> want to give the impression that I don't appreciate it. Was just hoping
> to revisit these in the context of v9 since there were some concerning
> things in flight WRT the spec handling and I was sort of focused on
> getting ahead of those in case they involved firmware/spec changes. But
> I realize that's resulted in a waste of your time and I should have at
> least provided some indication of where I was with these before your
> review. Won't happen again.

Thanks, that's appreciated.

And in case you're wondering, the kernel is the most flexible thing from
all parties involved so even if you have to change the spec/fw, fixing
the kernel is a lot easier than any of the other things. So make sure
you do a good job with the spec/fw - the kernel will be fine. :-)

> Ok, will work this in for v10. My plan is to introduce this struct:
> 
>   struct cpuid_leaf {
>       u32 fn;
>       u32 subfn;
>       u32 eax;
>       u32 ebx;
>       u32 ecx;
>       u32 edx;
>   }

Ok.

> as part of the patch which introduces sev_cpuid_hv():
> 
>   x86/sev: Move MSR-based VMGEXITs for CPUID to helper
> 
> and then utilize that for the function parameters there, here, and any
> other patches in the SNP code involved with fetching/manipulating cpuid
> values before returning them to the #VC handler.

Sounds good.

Thx.

-- 
Regards/Gruss,
    Boris.

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