linux-kernel - Re: [PATCH v5 09/12] x86/tdx: Wire up KVM hypercalls

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Date:   Tue, 24 Aug 2021 21:39:17 +0200
From:   Borislav Petkov <bp@...en8.de>
To:     "Kuppuswamy, Sathyanarayanan" 
        <sathyanarayanan.kuppuswamy@...ux.intel.com>
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Andy Lutomirski <luto@...nel.org>,
        Peter H Anvin <hpa@...or.com>,
        Dave Hansen <dave.hansen@...el.com>,
        Tony Luck <tony.luck@...el.com>,
        Dan Williams <dan.j.williams@...el.com>,
        Andi Kleen <ak@...ux.intel.com>,
        Kirill Shutemov <kirill.shutemov@...ux.intel.com>,
        Sean Christopherson <seanjc@...gle.com>,
        Kuppuswamy Sathyanarayanan <knsathya@...nel.org>,
        x86@...nel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v5 09/12] x86/tdx: Wire up KVM hypercalls

On Tue, Aug 24, 2021 at 12:11:00PM -0700, Kuppuswamy, Sathyanarayanan wrote:
> If the TDX code is complied for another hypervior, we need some config to
> disable above the above code.

Isn't that what CONFIG_KVM_GUEST is for?

Also, if they don't get used anywhere, the compiler will simply discard
them. I still don't see the need for the ifdeffery.

> Following is the error info.
> 
> WARNING: modpost: EXPORT symbol "__tdx_hypercall" [vmlinux] version
> generation failed, symbol will not be versioned.
> 
> So to fix the above issue, added tdx.h in arch/x86/include/asm/asm-prototypes.h

You need the C-style declaration of __tdx_hypercall, see

334bb7738764 ("x86/kbuild: enable modversions for symbols exported from asm")

and you can do the include without the ifdeffery.

And also state in the commit message why you're including it.

Thx.

-- 
Regards/Gruss,
    Boris.

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