linux-kernel - Re: [PATCH v6 08/42] x86/sev-es: initialize sev

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Date:   Thu, 21 Oct 2021 16:28:07 +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>,
        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>,
        tony.luck@...el.com, marcorr@...gle.com,
        sathyanarayanan.kuppuswamy@...ux.intel.com
Subject: Re: [PATCH v6 08/42] x86/sev-es: initialize sev_status/features
 within #VC handler

On Wed, Oct 20, 2021 at 07:35:35PM -0500, Michael Roth wrote:
> Fortunately, all the code makes use of sev_status to get at the SEV MSR
> bits, so breaking the appropriate bits out of sme_enable() into an earlier
> sev_init() routine that's the exclusive writer of sev_status sounds like a
> promising approach.

Ack.

> It makes sense to do it immediately after the first #VC handler is set
> up, so CPUID is available, and since that's where SNP CPUID table
> initialization would need to happen if it's to be made available in
> #VC handler.

Right, and you can do all your init/CPUID prep there.

> It may even be similar enough between boot/compressed and run-time kernel
> that it could be a shared routine in sev-shared.c.

Uuh, bonus points! :-)

> But then again it also sounds like the appropriate place to move the
> snp_cpuid_init*() calls, and locating the cc_blob, and since there's
> differences there it might make sense to keep the boot/compressed and
> kernel proper sev_init() routines separate to avoid #ifdeffery).
>
> Not to get ahead of myself though. Just seems like a good starting point
> for how to consolidate the various users.

I like how you're thinking. :)

> Got it, and my apologies if I've given you that impression as it's
> certainly not my intent. (though I'm sure you've heard that before.)

Nothing to apologize - all good.

> Agreed, if we need to check SEV MSR early for the purposes of SNP it makes
> sense to move the overall SEV feature detection code earlier as well. I
> should have looked into that aspect more closely before introducing the
> changes.

Thx.

-- 
Regards/Gruss,
    Boris.

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