Re: [PATCH v7 04/20] x86/virt/tdx: Add skeleton to initialize TDX on demand

[Huang, Kai]

On Wed, 2022-11-23 at 08:58 -0800, Dave Hansen wrote:
> On 11/23/22 02:18, Huang, Kai wrote:
> > > Again, there are a lot of words in that comment, but I'm not sure why
> > > it's here.  Despite all the whinging about ACPI, doesn't it boil down to:
> > > 
> > >       The TDX module itself establishes its own concept of how many
> > >       logical CPUs there are in the system when it is loaded.
> > > 
> > This isn't accurate.  TDX MCHECK records the total number of logical CPUs when
> > the BIOS enables TDX.  This happens before the TDX module is loaded.  In fact
> > the TDX module only gets this information from a secret location.
> 
> Kai, this is the point where I lose patience with the conversation
> around this series.  I'll you paste you the line of code where the TDX
> module literally "establishes its own concept of how many logical CPUs
> there are in the system":
> 
> >     //NUM_LPS
> >     tdx_global_data_ptr->num_of_lps = sysinfo_table_ptr->mcheck_fields.tot_num_lps;
> 
> Yes, this is derived directly from MCHECK.  But, this concept is
> separate from MCHECK.  We have seen zero actual facts from you or other
> folks at Intel that this is anything other than an arbitrary choice made
> for the convenience of the TDX module.  It _might_ not be this way.  I'm
> open to hearing those facts and changing my position on this.
> 
> But, please bring facts, not random references to "secret locations"
> that aren't that secret.

Agreed.  Thanks for providing the comment and will use it.