linux-kernel - Re: [PATCH v19 069/130] KVM: TDX: Require TDP MMU and mmio caching for TDX

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Message-ID: <20240328210342.GR2444378@ls.amr.corp.intel.com>
Date: Thu, 28 Mar 2024 14:03:42 -0700
From: Isaku Yamahata <isaku.yamahata@...el.com>
To: Binbin Wu <binbin.wu@...ux.intel.com>
Cc: isaku.yamahata@...el.com, kvm@...r.kernel.org,
	linux-kernel@...r.kernel.org, isaku.yamahata@...il.com,
	Paolo Bonzini <pbonzini@...hat.com>, erdemaktas@...gle.com,
	Sean Christopherson <seanjc@...gle.com>,
	Sagi Shahar <sagis@...gle.com>, Kai Huang <kai.huang@...el.com>,
	chen.bo@...el.com, hang.yuan@...el.com, tina.zhang@...el.com,
	isaku.yamahata@...ux.intel.com
Subject: Re: [PATCH v19 069/130] KVM: TDX: Require TDP MMU and mmio caching
 for TDX

On Thu, Mar 28, 2024 at 01:24:27PM +0800,
Binbin Wu <binbin.wu@...ux.intel.com> wrote:

> 
> 
> On 2/26/2024 4:26 PM, isaku.yamahata@...el.com wrote:
> > From: Isaku Yamahata <isaku.yamahata@...el.com>
> > 
> > As TDP MMU is becoming main stream than the legacy MMU, the legacy MMU
> > support for TDX isn't implemented.  TDX requires KVM mmio caching.
> 
> Can you add some description about why TDX requires mmio caching in the
> changelog?

Sure, will update the commit log.

As the TDX guest is protected, the guest has to issue TDG.VP.VMCALL<MMIO> on
VE.  The VMM has to setup Shared-EPT entry to inject VE by setting the entry
value with VE suppress bit cleared.

KVM mmio caching is a feature to set the EPT entry to special value for MMIO GFN
instead of the default value with suppress VE bit set.  So TDX KVM wants to
utilize it.

Thanks,
-- 
Isaku Yamahata <isaku.yamahata@...el.com>