linux-kernel - Re: [RFC PATCH 3/4] KVM: TDX: Exit to userspace for GetTdVmCallInfo

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Message-ID: <aEnHYjTGofgGiDTH@google.com>
Date: Wed, 11 Jun 2025 11:13:54 -0700
From: Sean Christopherson <seanjc@...gle.com>
To: Rick P Edgecombe <rick.p.edgecombe@...el.com>
Cc: "mikko.ylinen@...ux.intel.com" <mikko.ylinen@...ux.intel.com>, 
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>, Kai Huang <kai.huang@...el.com>, 
	"binbin.wu@...ux.intel.com" <binbin.wu@...ux.intel.com>, Jiewen Yao <jiewen.yao@...el.com>, 
	Xiaoyao Li <xiaoyao.li@...el.com>, Tony Lindgren <tony.lindgren@...el.com>, 
	Adrian Hunter <adrian.hunter@...el.com>, Reinette Chatre <reinette.chatre@...el.com>, 
	"kvm@...r.kernel.org" <kvm@...r.kernel.org>, Yan Y Zhao <yan.y.zhao@...el.com>, 
	Isaku Yamahata <isaku.yamahata@...el.com>, "pbonzini@...hat.com" <pbonzini@...hat.com>, 
	Kirill Shutemov <kirill.shutemov@...el.com>
Subject: Re: [RFC PATCH 3/4] KVM: TDX: Exit to userspace for GetTdVmCallInfo

On Wed, Jun 11, 2025, Rick P Edgecombe wrote:
> On Wed, 2025-06-11 at 09:26 -0700, Sean Christopherson wrote:
> > > GetQuote is not part of the "Base" TDVMCALLs and so has a bit in
> > > GetTdVmCallInfo. We could move it to base?
> > 
> > Is GetQuote actually optional?  TDX without attestation seems rather
> > pointless.
> 
> I don't know if that was a consideration for why it got added to the optional
> category. The inputs were gathered from more than just Linux.

If there's an actual use case for TDX without attestation, then by all means,
make it optional.  I'm genuinely curious if there's a hypervisor that plans on
productizing TDX without supporting attestation.  It's entirely possible (likely?)
I'm missing or forgetting something.