linux-kernel - Re: [PATCH v8 01/40] x86/compressed/64: detect/setup SEV/SME features earlier in boot

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Date:   Wed, 15 Dec 2021 12:57:42 +0100
From:   Borislav Petkov <bp@...en8.de>
To:     Venu Busireddy <venu.busireddy@...cle.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>,
        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 01/40] x86/compressed/64: detect/setup SEV/SME
 features earlier in boot

On Tue, Dec 14, 2021 at 06:14:34PM -0600, Venu Busireddy wrote:
> diff --git a/arch/x86/include/asm/processor.h b/arch/x86/include/asm/processor.h
> index 2c5f12ae7d04..41b096f28d02 100644
> --- a/arch/x86/include/asm/processor.h
> +++ b/arch/x86/include/asm/processor.h
> @@ -224,6 +224,43 @@ static inline void native_cpuid(unsigned int *eax, unsigned int *ebx,
>  	    : "memory");
>  }
>  
> +/*
> + * Returns the pagetable bit position in pt_bit_pos,
> + * iff the specified features are supported.
> + */
> +static inline int get_pagetable_bit_pos(unsigned long *pt_bit_pos,
> +					unsigned long features)

You can simply return pt_bit_pos:

static inline unsigned int get_pagetable_bit_pos(unsigned long features)

and return a negative value on error.

Also, the only duplication this is saving is visual - that function will
get inlined at the call sites.

Also, I'd love to separate the compressed kernel headers from the
kernel proper ones but I'm afraid that ship has sailed. But if I could,
that would have to be in a special header that gets included by both
stages...

So I don't mind this but I'd let Brijesh and Tom have a look at it too.

Thx.

-- 
Regards/Gruss,
    Boris.

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