Re: [PATCH v4 12/12] x86/virt/tdx: Adjust 'struct tdx_module_args' to use x86 "register index" layout

[Huang, Kai]

On Sat, 2023-08-26 at 02:44 +0300, kirill.shutemov@xxxxxxxxxxxxxxx wrote:
> On Tue, Aug 15, 2023 at 11:02:06PM +1200, Kai Huang wrote:
> > diff --git a/arch/x86/include/asm/shared/tdx.h b/arch/x86/include/asm/shared/tdx.h
> > index 74fc466dfdcd..8d1427562c63 100644
> > --- a/arch/x86/include/asm/shared/tdx.h
> > +++ b/arch/x86/include/asm/shared/tdx.h
> > @@ -58,24 +58,31 @@
> >   * Used in __tdcall*() to gather the input/output registers' values of the
> >   * TDCALL instruction when requesting services from the TDX module. This is a
> >   * software only structure and not part of the TDX module/VMM ABI
> > + *
> > + * Note those *_unused are not used by the TDX_MODULE_CALL assembly.
> > + * The layout of this structure also matches KVM's kvm_vcpu_arch::regs[]
> > + * layout, which follows the "register index" order of x86 GPRs.  KVM
> > + * then can simply type cast kvm_vcpu_arch::regs[] to this structure to
> > + * avoid the extra memory copy between two structures when making
> > + * TDH.VP.ENTER SEAMCALL.
> 
> I still don't like KVM details leak here. I don't feel strong enough about
> it to NAK the patch, but...
> 

I am fine dropping it.  It's an optimization anyway.

I'll leave to Peter. :-)