linux-kernel - Re: [PATCH v19 110/130] KVM: TDX: Handle TDX PV MMIO hypercall

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Date: Tue, 25 Jun 2024 21:09:25 +0000
From: "Edgecombe, Rick P" <rick.p.edgecombe@...el.com>
To: "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"binbin.wu@...ux.intel.com" <binbin.wu@...ux.intel.com>, "Yamahata, Isaku"
	<isaku.yamahata@...el.com>
CC: "Zhang, Tina" <tina.zhang@...el.com>, "seanjc@...gle.com"
	<seanjc@...gle.com>, "Yuan, Hang" <hang.yuan@...el.com>, "Huang, Kai"
	<kai.huang@...el.com>, "Chen, Bo2" <chen.bo@...el.com>, "sagis@...gle.com"
	<sagis@...gle.com>, "isaku.yamahata@...il.com" <isaku.yamahata@...il.com>,
	"Aktas, Erdem" <erdemaktas@...gle.com>, "Chatre, Reinette"
	<reinette.chatre@...el.com>, "pbonzini@...hat.com" <pbonzini@...hat.com>,
	"sean.j.christopherson@...el.com" <sean.j.christopherson@...el.com>
Subject: Re: [PATCH v19 110/130] KVM: TDX: Handle TDX PV MMIO hypercall

On Tue, 2024-06-25 at 14:54 +0800, Binbin Wu wrote:
> > +               gpa = vcpu->mmio_fragments[0].gpa;
> > +               size = vcpu->mmio_fragments[0].len;
> 
> Since MMIO cross page boundary is not allowed according to the input 
> checks from TDVMCALL, these mmio_fragments[] is not needed.
> Just use vcpu->run->mmio.phys_addr and vcpu->run->mmio.len?

Can we add a comment or something to that check, on why KVM doesn't handle it?
Is it documented somewhere in the TDX ABI that it is not expected to be
supported?