Re: [PATCH v10 03/11] x86/cpufeatures: Add TDX Guest CPU feature

[Sathyanarayanan Kuppuswamy]

On 10/13/21 2:37 PM, Borislav Petkov wrote:
> On Wed, Oct 13, 2021 at 11:25:35PM +0200, Thomas Gleixner wrote:
> > So this ends up in doing:
> >
> >     use();
> >     init();
> >
> > Can you spot what's wrong with that?
> >
> > That's a clear violation of common sense and is simply not going to
> > happen. Why? If you think about deep defensive programming then use()
> > will look like this:
> >
> > use()
> > {
> >          assert(initialized);
> > }
> >
> > which is not something made up. It's a fundamental principle of
> > programming and some languages enforce that for very good reasons.
> >
> > Just because it can be done in C is no justification.
> Oh, I heartily agree.
>   
> > What's wrong with:
> >
> > x86_64_start_kernel()
> >
> >      tdx_early_init();
> >
> >      copy_bootdata();
> >      
> >      tdx_late_init();
> >
> > Absolutely nothing. It's clear, simple and well defined.
> I like simple more than anyone, so sure, I'd prefer that a lot more.
>
> And so the options parsing would need to happen early using, say,
> cmdline_find_option() or so, like sme_enable() does.

Since in tdx_early_init() all we are going to do is to initialize
"tdx_guest_detected" using cpuid call, shall we name it
tdx_guest_cpuid_init()? (similar to sme_enable call in AMD)

> Hmmm.
--
Sathyanarayanan Kuppuswamy
Linux Kernel Developer