linux-kernel - Re: [PATCH v7 02/45] x86/sev: detect/setup SEV/SME features earlier in boot

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Message-ID: <YZT/eBLQnQOVejzp@zn.tnic>
Date:   Wed, 17 Nov 2021 14:11:20 +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>,
        tony.luck@...el.com, marcorr@...gle.com,
        sathyanarayanan.kuppuswamy@...ux.intel.com
Subject: Re: [PATCH v7 02/45] x86/sev: detect/setup SEV/SME features earlier
 in boot

On Mon, Nov 15, 2021 at 02:17:15PM -0600, Michael Roth wrote:
> but in order for that to happen soon enough to make use of the CPUID
> table for all CPUID intructions, it needs to be moved to just after the first
> #VC handler is setup (where snp_cpuid_init() used to be in v6).

So, it needs to happen after the initial IDT is loaded on the BSP in
startup_64_setup_env().

So why don't you call sme_enable() right after the
startup_64_setup_env() call and add a comment above it to explain why
this call needs to happen there?

Instead of sticking that call in startup_64_setup_env() where it doesn't
belong conceptually - enabling SME doesn't really have anything to do
with setting up early environment...

Hmm.

-- 
Regards/Gruss,
    Boris.

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