linux-kernel - Re: [RFC v2 10/32] x86/tdx: Wire up KVM hypercalls

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Date:   Thu, 13 May 2021 12:33:14 -0700
From:   Dave Hansen <dave.hansen@...el.com>
To:     "Kuppuswamy, Sathyanarayanan" 
        <sathyanarayanan.kuppuswamy@...ux.intel.com>,
        "Kirill A. Shutemov" <kirill@...temov.name>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        Andy Lutomirski <luto@...nel.org>,
        Dan Williams <dan.j.williams@...el.com>,
        Tony Luck <tony.luck@...el.com>,
        Andi Kleen <ak@...ux.intel.com>,
        Kirill Shutemov <kirill.shutemov@...ux.intel.com>,
        Kuppuswamy Sathyanarayanan <knsathya@...nel.org>,
        Raj Ashok <ashok.raj@...el.com>,
        Sean Christopherson <seanjc@...gle.com>,
        linux-kernel@...r.kernel.org,
        Isaku Yamahata <isaku.yamahata@...el.com>
Subject: Re: [RFC v2 10/32] x86/tdx: Wire up KVM hypercalls

On 5/13/21 12:29 PM, Kuppuswamy, Sathyanarayanan wrote:
>> If there isn't, then the way we do it is adding another (invisible)
>> Kconfig variable to express the dependency for tdx-kvm.o:
>>
>> config INTEL_TDX_GUEST_KVM
>>     bool
>>     depends on KVM_GUEST && INTEL_TDX_GUEST
> 
> Currently it will only be used for KVM hypercall code. Will it to be
> overkill to create a new config over #ifdefs for this use case ? But,
> if this is the preferred approach, I will go with this suggestion.

You'll see this done lots of different (valid) ways over the kernel.
(#ifdef'd #including C files is not one of them.)

*My* preference is to use Kconfig in the way I described.  It keeps
makefiles and #ifdef's clean and obvious, relegating the logic to Kconfig.