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

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Date:   Wed, 12 May 2021 07:29:46 -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 5/12/21 7:10 AM, Kuppuswamy, Sathyanarayanan wrote:
> On 5/12/21 6:00 AM, Kirill A. Shutemov wrote:
>> This has to be compiled only for TDX+KVM.
> 
> Got it. So if we want to remove the "C" file include, we will have to
> add #ifdef CONFIG_KVM_GUEST in Makefile.
> 
> ifdef CONFIG_KVM_GUEST
> obj-$(CONFIG_INTEL_TDX_GUEST) += tdx-kvm.o
> #endif

Is there truly no dependency between CONFIG_KVM_GUEST and
CONFIG_INTEL_TDX_GUEST?

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