lkml.org 
[lkml]   [2022]   [Nov]   [22]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
From
SubjectRE: [PATCH 1/6] x86/tdx: Support hypercalls for TDX guests on Hyper-V
Date
> From: Dave Hansen <dave.hansen@intel.com>
> Sent: Monday, November 21, 2022 12:39 PM
> [...]
> On 11/21/22 11:51, Dexuan Cui wrote:
> > __tdx_hypercall() doesn't work for a TDX guest running on Hyper-V,
> > because Hyper-V uses a different calling convention, so add the
> > new function __tdx_ms_hv_hypercall().
>
> Other than R10 being variable here and fixed for __tdx_hypercall(), this
> looks *EXACTLY* the same as __tdx_hypercall(), or at least a strict
> subset of what __tdx_hypercall() can do.
>
> Did I miss something?

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() ?

> Another way of saying this: It seems like you could do this with a new
> version of _tdx_hypercall() (and all in C) instead of a new
> __tdx_hypercall().

I don't think the current TDVMCALL_EXPOSE_REGS_MASK allows me
to pass through RDX and R8 to Hyper-V.

PS, the comment before __tdx_hypercall() contains this line:

"* RBX, RBP, RDI, RSI - Used to pass VMCALL sub function specific
arguments."

But it looks like currently RBX an RBP are not used at all in
arch/x86/coco/tdx/tdcall.S ?

\
 
 \ /
  Last update: 2022-11-23 02:39    [W:0.492 / U:0.272 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site