Re: [PATCH v2 16/25] KVM: TDX: Get system-wide info about TDX module on initialization

[Xiaoyao Li]

On 10/31/2024 5:37 PM, Tony Lindgren wrote:
> On Thu, Oct 31, 2024 at 05:23:57PM +0800, Xiaoyao Li wrote:
> > here it is to initialize the configurable CPUID bits that get reported to
> > userspace. Though TDX module doesn't allow them to be set in TD_PARAM for
> > KVM_TDX_INIT_VM, they get set to 0xff because KVM reuse these bits
> > EBX[23:16] as the interface for userspace to configure GPAW of TD guest
> > (implemented in setup_tdparams_eptp_controls() in patch 19). That's why they
> > need to be set as all-1 to allow userspace to configure.
> >
> > And the comment above it is wrong and vague. we need to change it to
> > something like
> >
> > 	/*
> >           * Though TDX module doesn't allow the configuration of guest
> >           * phys addr bits (EBX[23:16]), KVM uses it as the interface for
> >           * userspace to configure the GPAW. So need to report these bits
> >           * as configurable to userspace.
> >           */
>
> That sounds good to me.
>
> Hmm so care to check if we can also just leave out another "old module"
> comment in tdx_read_cpuid()?

That one did relate to old module, the module that without 
TDX_CONFIG_FLAGS_MAXGPA_VIRT reported in tdx_feature0.

I will sent an follow up patch to complement the handling if TDX module 
supports TDX_CONFIG_FLAGS_MAXGPA_VIRT.

> Regards,
>
> Tony