From 68e37f457881d222c68834920f4ffd6f668a2b77 Mon Sep 17 00:00:00 2001
From: Ceping Sun <cepingx.sun@intel.com>
Date: Wed, 8 Nov 2023 19:38:25 +0800
Subject: [PATCH] MdePkg/BaseLib: Update TdVmcall to always output the value in
 R11

REF: https://bugzilla.tianocore.org/show_bug.cgi?id=4572

According to section 3.2 of the [GHCI] spec, if the return status
of MapGPA is "TDG.VP.VMCALL_RETRY", TD must retry this operation
for the pages in the region starting at the GPA specified in R11.

Currently, TDVF has not handled the retry results and always clears
the R11 on unsuccessful return status. For this, the TdVmcall needs
to output the value of R11 on unsuccessful return status to handle
the retry results of MapGPA.

Reference:
[GHCI]: TDX Guest-Host-Communication Interface v1.0
https://cdrdv2.intel.com/v1/dl/getContent/726790

Cc: Liming Gao <gaoliming@byosoft.com.cn>
Cc: Michael D Kinney <michael.d.kinney@intel.com>
Cc: Erdem Aktas <erdemaktas@google.com>
Cc: James Bottomley <jejb@linux.ibm.com>
Cc: Min Xu <min.m.xu@intel.com>
Cc: Tom Lendacky <thomas.lendacky@amd.com>
Cc: Michael Roth <michael.roth@amd.com>
Acked-by: Gerd Hoffmann <kraxel@redhat.com>
Reviewed-by: Jiewen Yao <jiewen.yao@intel.com>
Reviewed-by: Liming Gao <gaoliming@byosoft.com.cn>
Signed-off-by: Ceping Sun <cepingx.sun@intel.com>
---
 MdePkg/Library/BaseLib/X64/TdVmcall.nasm | 4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/MdePkg/Library/BaseLib/X64/TdVmcall.nasm b/MdePkg/Library/BaseLib/X64/TdVmcall.nasm
index 5ecc10b171..8dd9bfcbfa 100644
--- a/MdePkg/Library/BaseLib/X64/TdVmcall.nasm
+++ b/MdePkg/Library/BaseLib/X64/TdVmcall.nasm
@@ -133,9 +133,7 @@ ASM_PFX(TdVmCall):
        test r9, r9
        jz .no_return_data
 
-       ; On success, propagate TDVMCALL output value to output param
-       test rax, rax
-       jnz .no_return_data
+       ; Propagate TDVMCALL output value to output param
        mov [r9], r11
 .no_return_data:
        tdcall_regs_postamble