Re: [PATCHv4 04/30] x86/tdx: Add __tdx_module_call() and __tdx_hypercall() helper functions

[Kirill A. Shutemov]

On Thu, Feb 24, 2022 at 09:01:42AM -0800, Dave Hansen wrote:
> On 2/24/22 07:56, Kirill A. Shutemov wrote:
> > +	tdcall
> > +
> > +	/*
> > +	 * TDVMCALL leaf does not suppose to fail. If it fails something
> > +	 * is horribly wrong with TDX module. Stop the world.
> > +	 */
> > +	testq %rax, %rax
> > +	jne .Lpanic
> 
> This should be:
> 
> 	"A TDVMCALL is not supposed to fail."
> 
> I also wish this was mentioning something about the difference between a
> failure and return code.
> 
> 	/*
> 	 * %rax==0 indicates a failure of the TDVMCALL mechanism itself
> 	 * and that something has gone horribly wrong with the TDX
> 	 * module.
> 	 *
> 	 * The return status of the hypercall operation is separate
> 	 * (in %r10).  Hypercall errors are a part of normal operation
> 	 * and are handled by callers.
> 	 */
> 
> I've been confused by this exact thing multiple times over the months
> that I've been looking at this code.  I think it deserves a good comment.

Sure. The updated patch is below.