Re: [PATCH v3 07/12] x86/tdx: Make TDX_HYPERCALL asm similar to TDX_MODULE_CALL

[kirill.shutemov@xxxxxxxxxxxxxxx]

On Thu, Aug 03, 2023 at 11:56:40AM +0000, Huang, Kai wrote:
> On Thu, 2023-08-03 at 14:45 +0300, kirill.shutemov@xxxxxxxxxxxxxxx wrote:
> > > > I would rather keep the struct
> > > > read-only where possible.
> > > > 
> > > 
> > > We can achieve this if there's a clean way to do, but I don't see that.
> > 
> > Keep _ret() and non-_ret() versions?
> 
> The problem is the assembly needs to always turn on the "\ret" so that the R10
> (used as VP.VMCALL leaf return code) can be saved to the structure.  Otherwise
> we are not able to return VP.VMCALL leaf return code.

Yeah. This is downside of single assembly macro for all calls.

One possible way is to make it in C: non-_ret() version pass to the
assembly helper copy of the caller's struct, keeping original intact.
But, yeah, it is ugly.

-- 
  Kiryl Shutsemau / Kirill A. Shutemov