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

Isaku Yamahata
2024-03-28T21:03:43Z

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

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