[edk2-devel] [PATCH V2 1/2] MdePkg/BaseLib: Update TdVmcall to always output the value in R11

["sunceping" <cepingx.sun@intel.com>]

From: Ceping Sun <cepingx.sun@intel.com>

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: Jiewen Yao <jiewen.yao@intel.com>
Cc: Min Xu <min.m.xu@intel.com>
Cc: Tom Lendacky <thomas.lendacky@amd.com>
Cc: Michael Roth <michael.roth@amd.com>
Cc: Gerd Hoffmann <kraxel@redhat.com>
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 5ecc10b17193..8dd9bfcbfa14 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
-- 
2.34.1



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