linux-kernel - Re: [PATCH v9 05/43] x86/compressed/64: Detect/setup SEV/SME features earlier in boot

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Date:   Tue, 1 Feb 2022 19:08:21 +0100
From:   Borislav Petkov <bp@...en8.de>
To:     Brijesh Singh <brijesh.singh@....com>
Cc:     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>,
        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>,
        brijesh.ksingh@...il.com, tony.luck@...el.com, marcorr@...gle.com,
        sathyanarayanan.kuppuswamy@...ux.intel.com
Subject: Re: [PATCH v9 05/43] x86/compressed/64: Detect/setup SEV/SME
 features earlier in boot

On Fri, Jan 28, 2022 at 11:17:26AM -0600, Brijesh Singh wrote:
> diff --git a/arch/x86/boot/compressed/head_64.S b/arch/x86/boot/compressed/head_64.S
> index fd9441f40457..49064a9f96e2 100644
> --- a/arch/x86/boot/compressed/head_64.S
> +++ b/arch/x86/boot/compressed/head_64.S
> @@ -191,9 +191,8 @@ SYM_FUNC_START(startup_32)
>  	/*
>  	 * Mark SEV as active in sev_status so that startup32_check_sev_cbit()
>  	 * will do a check. The sev_status memory will be fully initialized

That "sev_status memory" formulation is just weird. Pls fix it while
you're touching that comment.

> +static inline u64 rd_sev_status_msr(void)
> +{
> +	unsigned long low, high;
> +
> +	asm volatile("rdmsr" : "=a" (low), "=d" (high) :
> +			"c" (MSR_AMD64_SEV));
> +
> +	return ((high << 32) | low);
> +}

Don't you see sev_es_rd_ghcb_msr() in that same file above? Do a common
rdmsr() helper and call it where needed, pls, instead of duplicating
code.

misc.h looks like a good place.

Extra bonus points will be given if you unify callers in
arch/x86/boot/cpucheck.c too but you don't have to - I can do that
ontop.

Thx.

-- 
Regards/Gruss,
    Boris.

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