linux-kernel - Re: [PATCH v9 33/43] x86/compressed: Add SEV-SNP feature detection/setup

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Message-ID: <YgKF6kzR87WuXj/a@zn.tnic>
Date:   Tue, 8 Feb 2022 16:02:02 +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>,
        brijesh.ksingh@...il.com, tony.luck@...el.com, marcorr@...gle.com,
        sathyanarayanan.kuppuswamy@...ux.intel.com
Subject: Re: [PATCH v9 33/43] x86/compressed: Add SEV-SNP feature
 detection/setup

On Tue, Feb 08, 2022 at 07:50:09AM -0600, Michael Roth wrote:
> I'm assuming that would be considered 'non-static' since it would need
> to be exported if sev-shared.c was compiled separately instead of
> directly #include'd.

No, that one can lose the prefix too. We'll cross that bridge when we
get to it.

> And then there's also these which are static helpers that are only used
> within sev-shared.c:
> 
>   snp_cpuid_info_get_ptr()

So looking at that one - and it felt weird reading that code because it
said "cpuid_info" but that's not an "info" - that should be:

struct snp_cpuid_table {
        u32 count;
        u32 __reserved1;
        u64 __reserved2;
        struct snp_cpuid_fn fn[SNP_CPUID_COUNT_MAX];
} __packed;

just call it what it is - a SNP CPUID *table*.

And then you can have

	const struct snp_cpuid_table *cpuid_tbl = snp_cpuid_get_table();

and that makes it crystal clear what this does.

>   snp_cpuid_calc_xsave_size()
>   snp_cpuid_get_validated_func()
>
>   snp_cpuid_check_range()

You can merge that small function into its only call site and put a
comment above the code:

	/* Check function is within the supported CPUID leafs ranges */

>   snp_cpuid_hv()
>   snp_cpuid_postprocess()
>   snp_cpuid()
> 
> but in those cases it seems useful to keep them grouped under the
> snp_cpuid_* prefix since they become ambiguous otherwise, and
> just using cpuid_* as a prefix (or suffix/etc) makes it unclear
> that they are only used for SNP and not for general CPUID handling.
> Should we leave those as-is?

Yap, the rest make sense to denote to what functionality they belong to.

Thx.

-- 
Regards/Gruss,
    Boris.

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