linux-kernel - Re: [PATCH v19 052/130] KVM: x86/mmu: Track shadow MMIO value on a per-VM basis

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Message-ID: <20240327235835.GI2444378@ls.amr.corp.intel.com>
Date: Wed, 27 Mar 2024 16:58:35 -0700
From: Isaku Yamahata <isaku.yamahata@...el.com>
To: "Edgecombe, Rick P" <rick.p.edgecombe@...el.com>
Cc: "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"Yamahata, Isaku" <isaku.yamahata@...el.com>,
	"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>,
	"pbonzini@...hat.com" <pbonzini@...hat.com>,
	"sean.j.christopherson@...el.com" <sean.j.christopherson@...el.com>,
	isaku.yamahata@...ux.intel.com
Subject: Re: [PATCH v19 052/130] KVM: x86/mmu: Track shadow MMIO value on a
 per-VM basis

On Tue, Mar 26, 2024 at 03:31:05AM +0000,
"Edgecombe, Rick P" <rick.p.edgecombe@...el.com> wrote:

> On Mon, 2024-02-26 at 00:25 -0800, isaku.yamahata@...el.com wrote:
> > From: Isaku Yamahata <isaku.yamahata@...el.com>
> > 
> > TDX will use a different shadow PTE entry value for MMIO from VMX.  Add
> > members to kvm_arch and track value for MMIO per-VM instead of global
> > variables.  By using the per-VM EPT entry value for MMIO, the existing VMX
> > logic is kept working.  Introduce a separate setter function so that guest
> > TD can override later.
> > 
> > Also require mmio spte caching for TDX.
> 
> 
> > Actually this is true case
> > because TDX requires EPT and KVM EPT allows mmio spte caching.
> > 
> 
> I can't understand what this is trying to say.

I'll drop this sentence as the logic moved to
"069/130 KVM: TDX: Require TDP MMU and mmio caching for TDX".


> >  {
> > +
> > +       kvm->arch.shadow_mmio_value = shadow_mmio_value;
> 
> It could use kvm_mmu_set_mmio_spte_value()?

Yes.
-- 
Isaku Yamahata <isaku.yamahata@...el.com>