x86/tdx: Reimplement __tdx_hypercall() using TDX_MODULE_CALL asm

Now the TDX_HYPERCALL asm is basically identical to the TDX_MODULE_CALL
with both '\saved' and '\ret' enabled, with two minor things though:

1) The way to restore the structure pointer is different

The TDX_HYPERCALL uses RCX as spare to restore the structure pointer,
but the TDX_MODULE_CALL assumes no spare register can be used.  In other
words, TDX_MODULE_CALL already covers what TDX_HYPERCALL does.

2) TDX_MODULE_CALL only clears shared registers for TDH.VP.ENTER

For this just need to make that code available for the non-host case.

Thus, remove the TDX_HYPERCALL and reimplement the __tdx_hypercall()
using the TDX_MODULE_CALL.

Extend the TDX_MODULE_CALL to cover "clear shared registers" for
TDG.VP.VMCALL.  Introduce a new __tdcall_saved_ret() to replace the
temporary __tdcall_hypercall().

The __tdcall_saved_ret() can also be used for those new TDCALLs which
require more input/output registers than the basic TDCALLs do.

Suggested-by: Peter Zijlstra <[email protected]>
Signed-off-by: Kai Huang <[email protected]>
Signed-off-by: Dave Hansen <[email protected]>
Reviewed-by: Kirill A. Shutemov <[email protected]>
Acked-by: Peter Zijlstra (Intel) <[email protected]>
Link: https://lore.kernel.org/all/e68a2473fb6f5bcd78b078cae7510e9d0753b3df.1692096753.git.kai.huang%40intel.com

1 files changed, 1 insertions, 1 deletions

diff --git a/arch/x86/include/asm/shared/tdx.h b/arch/x86/include/asm/shared/tdx.h
index 85493c4813cf..f53a41948946 100644
--- a/arch/x86/include/asm/shared/tdx.h
+++ b/arch/x86/include/asm/shared/tdx.h
@@ -83,6 +83,7 @@ struct tdx_module_args {
 /* Used to communicate with the TDX module */
 u64 __tdcall(u64 fn, struct tdx_module_args *args);
 u64 __tdcall_ret(u64 fn, struct tdx_module_args *args);
+u64 __tdcall_saved_ret(u64 fn, struct tdx_module_args *args);
 
 /*
  * Used in __tdx_hypercall() to pass down and get back registers' values of
@@ -106,7 +107,6 @@ struct tdx_hypercall_args {
 };
 
 /* Used to request services from the VMM */
-u64 __tdcall_hypercall(u64 fn, struct tdx_module_args *args);
 u64 __tdx_hypercall(struct tdx_hypercall_args *args);
 
 /*