Re: [PATCH 4/4] x86/tdx: Enable ENUM_TOPOLOGY

[Kirill A. Shutemov]

On Sat, Mar 09, 2024 at 07:56:11PM -0800, Kuppuswamy Sathyanarayanan wrote:
> 
> On 3/9/24 1:02 PM, Kirill A. Shutemov wrote:
> > TDX 1.0 generates a #VE when accessing topology-related CPUID leafs
> > (0xB and 0x1F) and the X2APIC_APICID MSR. The kernel returns all
> > zeros on CPUID #VEs. In practice, this means that the kernel can only
> > boot with a plain topology. Any complications will cause problems.
> 
> Is this issue only for TDX 1.0? What about TDX > 1.0?

TDX 1.0 defines the baseline for TDX. Any change in behaviour will be
gated by explicit opt-in. In this case, it is ENUM_TOPOLOGY.

> > The ENUM_TOPOLOGY feature allows the VMM to provide topology
> > information to the guest in a safe manner. Enabling the feature
> > eliminates topology-related #VEs: the TDX module virtualizes
> > accesses to the CPUID leafs and the MSR.
> >
> > Enable ENUM_TOPOLOGY if it is available.
> 
> I cant find the ENUM_TOPOLOGY in ABI spec (https://cdrdv2.intel.com/v1/dl/getContent/795381).
> 
> Can you point me to the correct document?

I guess JSON dump is out of sync with the PDF doc. See this:

https://cdrdv2.intel.com/v1/dl/getContent/733579

-- 
  Kiryl Shutsemau / Kirill A. Shutemov