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

[Isaku Yamahata]

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

> 
> 
> On 2/26/2024 4:26 PM, isaku.yamahata@xxxxxxxxx wrote:
> > From: Isaku Yamahata <isaku.yamahata@xxxxxxxxx>
> > 
> > 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@xxxxxxxxx>