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Date:   Wed, 26 Jan 2022 19:35:04 +0100
From:   Borislav Petkov <bp@alien8.de>
To:     Brijesh Singh <brijesh.singh@amd.com>
Cc:     x86@kernel.org, linux-kernel@vger.kernel.org, kvm@vger.kernel.org,
        linux-efi@vger.kernel.org, platform-driver-x86@vger.kernel.org,
        linux-coco@lists.linux.dev, linux-mm@kvack.org,
        Thomas Gleixner <tglx@linutronix.de>,
        Ingo Molnar <mingo@redhat.com>, Joerg Roedel <jroedel@suse.de>,
        Tom Lendacky <thomas.lendacky@amd.com>,
        "H. Peter Anvin" <hpa@zytor.com>, Ard Biesheuvel <ardb@kernel.org>,
        Paolo Bonzini <pbonzini@redhat.com>,
        Sean Christopherson <seanjc@google.com>,
        Vitaly Kuznetsov <vkuznets@redhat.com>,
        Jim Mattson <jmattson@google.com>,
        Andy Lutomirski <luto@kernel.org>,
        Dave Hansen <dave.hansen@linux.intel.com>,
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        Peter Zijlstra <peterz@infradead.org>,
        Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>,
        David Rientjes <rientjes@google.com>,
        Dov Murik <dovmurik@linux.ibm.com>,
        Tobin Feldman-Fitzthum <tobin@ibm.com>,
        Michael Roth <michael.roth@amd.com>,
        Vlastimil Babka <vbabka@suse.cz>,
        "Kirill A . Shutemov" <kirill@shutemov.name>,
        Andi Kleen <ak@linux.intel.com>,
        "Dr . David Alan Gilbert" <dgilbert@redhat.com>,
        tony.luck@intel.com, marcorr@google.com,
        sathyanarayanan.kuppuswamy@linux.intel.com
Subject: Re: [PATCH v8 35/40] x86/sev: use firmware-validated CPUID for
 SEV-SNP guests
Message-ID: <YfGUWLmg82G+l4jU@zn.tnic>
References: <20211210154332.11526-1-brijesh.singh@amd.com>
 <20211210154332.11526-36-brijesh.singh@amd.com>
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On Fri, Dec 10, 2021 at 09:43:27AM -0600, Brijesh Singh wrote:
> From: Michael Roth <michael.roth@amd.com>
> 
> SEV-SNP guests will be provided the location of special 'secrets' and
> 'CPUID' pages via the Confidential Computing blob. This blob is
> provided to the run-time kernel either through bootparams field that
						^
						a


> was initialized by the boot/compressed kernel, or via a setup_data
> structure as defined by the Linux Boot Protocol.
> 
> Locate the Confidential Computing from these sources and, if found,
				   ^
				   blob

> use the provided CPUID page/table address to create a copy that the
> run-time kernel will use when servicing cpuid instructions via a #VC
					  ^^^^^

Please capitalize all instruction mnemonics in text.

> +/*
> + * It is useful from an auditing/testing perspective to provide an easy way
> + * for the guest owner to know that the CPUID table has been initialized as
> + * expected, but that initialization happens too early in boot to print any
> + * sort of indicator, and there's not really any other good place to do it. So
> + * do it here, and while at it, go ahead and re-verify that nothing strange has
> + * happened between early boot and now.
> + */
> +static int __init snp_cpuid_check_status(void)

That function's redundant now, I believe, since we terminate the guest
if there's something wrong with the CPUID page.

-- 
Regards/Gruss,
    Boris.

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