linux-kernel - Re: [PATCH v8 20/40] x86/sev: Use SEV-SNP AP creation to start secondary CPUs

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Message-ID: <176b6163-fb2a-0339-e23f-2090ea78b4ed@intel.com>
Date:   Fri, 10 Dec 2021 10:50:19 -0800
From:   Dave Hansen <dave.hansen@...el.com>
To:     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
Cc:     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>,
        Borislav Petkov <bp@...en8.de>,
        Michael Roth <michael.roth@....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 v8 20/40] x86/sev: Use SEV-SNP AP creation to start
 secondary CPUs

On 12/10/21 7:43 AM, Brijesh Singh wrote:
> +	vmsa->efer		= 0x1000;	/* Must set SVME bit */
> +	vmsa->cr4		= cr4;
> +	vmsa->cr0		= 0x60000010;
> +	vmsa->dr7		= 0x400;
> +	vmsa->dr6		= 0xffff0ff0;
> +	vmsa->rflags		= 0x2;
> +	vmsa->g_pat		= 0x0007040600070406ULL;
> +	vmsa->xcr0		= 0x1;
> +	vmsa->mxcsr		= 0x1f80;
> +	vmsa->x87_ftw		= 0x5555;
> +	vmsa->x87_fcw		= 0x0040;

This is a big fat pile of magic numbers.  We also have nice macros for a
non-zero number of these, like:

	#define MXCSR_DEFAULT 0x1f80

I understand that this probably _works_ as-is, but it doesn't look very
friendly if someone else needs to go hack on it.