Re: [RFC PATCH 03/15] x86/tdx: Add TDG.TDI.RD module call wrapper for TDX Connect

[Xiaoyao Li <xiaoyao.li@intel.com>]

On 9/24/2026 12:10 PM, Zhenzhong Duan wrote:
> Introduce wrapper tdx_mcall_tdi_read() to provide tdx-guest driver with a
> standard interface for querying specific metadata fields from a target
> Trust Device Interface Control Structure (TDI_CS).
> 
> Explicitly mapping architectural TDX error codes into Linux POSIX errno
> with two helpers, introducing tdx_mcall_to_errno() to handle general
> module calls, while introducing tdx_mcall_tdi_to_errno() specifically for
> TDI related module calls.

Set aside why mapping architectural TDX error codes into Linux POSIX errno is
needed and what it brings, I think the common enabling order is one prep patch
to introduce tdx_mcall_to_errno() and turn existing users to use it. Then this
patch introduces tdx_mcall_tdi_to_errno() to use it as well.

> Unlike TDG.VP.VMCALL based hypercalls which communicate with the host,
> TDG.TDI.RD is a module call (mcall) that communicates directly with the
> TDX module. This distinction is reflected in the tdx_mcall_ naming
> prefix, as opposed to tdx_hcall_ used for host-directed hypercalls.

I would say this paragraph is not needed. It's not the first patch to introduce
hcall and mcall.

> Note that while host-bound hypercalls (such as tdx_hcall_tdcm()) pass a
> platform-specific Device Identifier (devid), the func_id parameter used
> here is defined by the TDISP standard (refer to Section 11.2 "TDISP
> rules"). Although these values result in the same underlying bit format
> when the PCI segment is zero, they represent separate structural
> abstractions in their respective specifications.

This paragraph seems to provide help but it doesn't look to help (at least for
me). Because until now there are only the helper defined but no user, I still
don't know what specific values will be passed to them.

> Signed-off-by: Zhenzhong Duan <zhenzhong.duan@intel.com>
> ---
>  arch/x86/coco/tdx/tdx.c           |  5 ----
>  arch/x86/coco/tdx/tdx_connect.c   | 41 +++++++++++++++++++++++++++++++
>  arch/x86/include/asm/shared/tdx.h |  1 +
>  arch/x86/include/asm/tdx.h        | 20 +++++++++++++++
>  4 files changed, 62 insertions(+), 5 deletions(-)
> 

...

> diff --git a/arch/x86/include/asm/shared/tdx.h b/arch/x86/include/asm/shared/tdx.h
> index f46a3171a512..665c12925ff6 100644
> --- a/arch/x86/include/asm/shared/tdx.h
> +++ b/arch/x86/include/asm/shared/tdx.h
> @@ -20,6 +20,7 @@
>  #define TDG_MEM_PAGE_ACCEPT		6
>  #define TDG_VM_RD			7
>  #define TDG_VM_WR			8
> +#define TDG_TDI_READ			67

Please name it TDG_TDI_RD to keep it consistent with TDG_VM_RD