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

["Yao, Jiewen" <jiewen.yao@intel.com>]

Reviewed-by: Jiewen Yao <Jiewen.yao@intel.com>

> -----Original Message-----
> From: Sun, CepingX <cepingx.sun@intel.com>
> Sent: Thursday, November 2, 2023 5:10 PM
> To: devel@edk2.groups.io
> Cc: Sun, CepingX <cepingx.sun@intel.com>; Gao, Liming
> <gaoliming@byosoft.com.cn>; Kinney, Michael D <michael.d.kinney@intel.com>;
> Aktas, Erdem <erdemaktas@google.com>; James Bottomley
> <jejb@linux.ibm.com>; Yao, Jiewen <jiewen.yao@intel.com>; Xu, Min M
> <min.m.xu@intel.com>; Tom Lendacky <thomas.lendacky@amd.com>; Michael
> Roth <michael.roth@amd.com>; Gerd Hoffmann <kraxel@redhat.com>
> Subject: [PATCH V2 1/2] MdePkg/BaseLib: Update TdVmcall to always output the
> value in R11
> 
> 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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