RE: [PATCH 1/6] x86/tdx: Support hypercalls for TDX guests on Hyper-V

[Dexuan Cui]

> From: Dave Hansen <dave.hansen@xxxxxxxxx>
> Sent: Wednesday, November 23, 2022 8:05 AM
> On 11/22/22 17:56, Dexuan Cui wrote:
> >> From: Dexuan Cui
> >> [...]
> >> The existing asm code for __tdx_hypercall() passes through R10~R15
> >> (see TDVMCALL_EXPOSE_REGS_MASK) to the (KVM) hypervisor.
> >>
> >> Unluckily, for Hyper-V, we need to pass through RDX, R8, R10 and R11
> >> to Hyper-V, so I don't think I can use the existing __tdx_hypercall() ?
> > I'm checking with the Hyper-V team to see if it's possible for them
> > to not use RDX and R8, and use R12 and R13 instead. Will keep the
> > thread updated.
> 
> That would be nice.  But, to be honest, I don't expect them to change
> the ABI for one OS.  It's not a big deal to just make the function a bit
> more flexible.

Then I'll implement a C function using __tdx_hypercall() that will
be expaneed by Kirill. Thank you all for the suggestions!