Re: [PATCH v3 05/12] x86/tdx: Pass TDCALL/SEAMCALL input/output registers via a structure

[kirill . shutemov]

On Wed, Jul 26, 2023 at 11:25:07PM +1200, Kai Huang wrote:
> diff --git a/arch/x86/virt/vmx/tdx/tdxcall.S b/arch/x86/virt/vmx/tdx/tdxcall.S
> index 6bdf6e137953..a0e7fe81bf63 100644
> --- a/arch/x86/virt/vmx/tdx/tdxcall.S
> +++ b/arch/x86/virt/vmx/tdx/tdxcall.S
> @@ -17,34 +17,33 @@
>   *            TDX module and hypercalls to the VMM.
>   * SEAMCALL - used by TDX hosts to make requests to the
>   *            TDX module.
> + *
> + *-------------------------------------------------------------------------
> + * TDCALL/SEAMCALL ABI:
> + *-------------------------------------------------------------------------
> + * Input Registers:
> + *
> + * RAX                 - TDCALL/SEAMCALL Leaf number.
> + * RCX,RDX,R8-R9       - TDCALL/SEAMCALL Leaf specific input registers.
> + *
> + * Output Registers:
> + *
> + * RAX                 - TDCALL/SEAMCALL instruction error code.
> + * RCX,RDX,R8-R11      - TDCALL/SEAMCALL Leaf specific output registers.
> + *
> + *-------------------------------------------------------------------------

So, you keep the existing asymetry in IN and OUT registers. R10 and R11
are OUT-only registers. It can be confusing for user since it is the same
structure now. I guess it changes in the following patches, but I would
prefer to make them even here if there's no good reason not to.

-- 
  Kiryl Shutsemau / Kirill A. Shutemov