linux-kernel - Re: [PATCH v2 2/7] KVM: x86: Extract VMXON and EFER.SVME enablement to kernel

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Message-ID: <aTmBobJJo_sFbre9@google.com>
Date: Wed, 10 Dec 2025 06:20:17 -0800
From: Sean Christopherson <seanjc@...gle.com>
To: dan.j.williams@...el.com
Cc: Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>, 
	Dave Hansen <dave.hansen@...ux.intel.com>, x86@...nel.org, 
	Kiryl Shutsemau <kas@...nel.org>, Paolo Bonzini <pbonzini@...hat.com>, linux-kernel@...r.kernel.org, 
	linux-coco@...ts.linux.dev, kvm@...r.kernel.org, 
	Chao Gao <chao.gao@...el.com>
Subject: Re: [PATCH v2 2/7] KVM: x86: Extract VMXON and EFER.SVME enablement
 to kernel

On Wed, Dec 10, 2025, dan.j.williams@...el.com wrote:
> Sean Christopherson wrote:
> > On Sat, Dec 06, 2025, dan.j.williams@...el.com wrote:
> > I don't think we need anything at this time.  INTEL_TDX_HOST depends on KVM_INTEL,
> > and so without a user that needs VMXON without KVM_INTEL, I think we're good as-is.
> > 
> >  config INTEL_TDX_HOST
> > 	bool "Intel Trust Domain Extensions (TDX) host support"
> > 	depends on CPU_SUP_INTEL
> > 	depends on X86_64
> > 	depends on KVM_INTEL
> 
> ...but INTEL_TDX_HOST, it turns out, does not have any functional
> dependencies on KVM_INTEL. At least, not since I last checked. Yes, it
> would be silly and result in dead code today to do a build with:
> 
> CONFIG_INTEL_TDX_HOST=y
> CONFIG_KVM_INTEL=n
> 
> However, when the TDX Connect support arrives you could have:
> 
> CONFIG_INTEL_TDX_HOST=y
> CONFIG_KVM_INTEL=n
> CONFIG_TDX_HOST_SERVICES=y
> 
> Where "TDX Host Services" is a driver for PCIe Link Encryption and TDX
> Module update. Whether such configuration freedom has any practical
> value is a separate question.
> 
> I am ok if the answer is, "wait until someone shows up who really wants
> PCIe Link Encryption without KVM".

Ya, that's my answer.  At the very least, wait until TDX_HOST_SERVICES comes
along.