回复: [edk2-devel] [PATCH v1 1/1] Fix AsmReadMsr64() and AsmWriteMsr64() with GCC toolchain

[gaoliming]

Naito:
  The fix is correct. Reviewed-by: Liming Gao <gaoliming at byosoft.com.cn>

Thanks
Liming 
> -----邮件原件-----
> 发件人: devel at edk2.groups.io <devel at edk2.groups.io> 代表 Takuto Naito
> 发送时间: 2021年4月12日 23:07
> 收件人: devel at edk2.groups.io
> 抄送: Takuto Naito <naitaku at gmail.com>; Michael D Kinney
> <michael.d.kinney at intel.com>; Liming Gao <gaoliming at byosoft.com.cn>;
> Zhiguang Liu <zhiguang.liu at intel.com>
> 主题: [edk2-devel] [PATCH v1 1/1] Fix AsmReadMsr64() and AsmWriteMsr64()
> with GCC toolchain
> 
> REF: https://bugzilla.tianocore.org/show_bug.cgi?id=3325
> 
> 1. AsmReadMsr64() in X64/GccInlinePriv.c
> AsmReadMsr64 can return uninitialized value if FilterBeforeMsrRead
> returns False. This causes build error with the CLANG toolchain.
> 
> 2. AsmWriteMsr64() in X64/GccInlinePriv.c
> In the case that FilterBeforeMsrWrite changes Value and returns True,
> The original Value, not the changed Value, is written to the MSR.
> This behavior is different from the one of AsmWriteMsr64() in
> X64/WriteMsr64.c for the MSFT toolchain.
> 
> Signed-off-by: Takuto Naito <naitaku at gmail.com>
> Cc: Michael D Kinney <michael.d.kinney at intel.com>
> Cc: Liming Gao <gaoliming at byosoft.com.cn>
> Cc: Zhiguang Liu <zhiguang.liu at intel.com>
> ---
>  MdePkg/Library/BaseLib/X64/GccInlinePriv.c | 7 +++----
>  1 file changed, 3 insertions(+), 4 deletions(-)
> 
> diff --git a/MdePkg/Library/BaseLib/X64/GccInlinePriv.c
> b/MdePkg/Library/BaseLib/X64/GccInlinePriv.c
> index e4920f2116..244bd62ee6 100644
> --- a/MdePkg/Library/BaseLib/X64/GccInlinePriv.c
> +++ b/MdePkg/Library/BaseLib/X64/GccInlinePriv.c
> @@ -80,7 +80,7 @@ AsmReadMsr64 (
>    }
>    FilterAfterMsrRead (Index, &Value);
> 
> -  return (((UINT64)HighData) << 32) | LowData;
> +  return Value;
>  }
> 
>  /**
> @@ -111,11 +111,10 @@ AsmWriteMsr64 (
>    UINT32 HighData;
>    BOOLEAN Flag;
> 
> -  LowData  = (UINT32)(Value);
> -  HighData = (UINT32)(Value >> 32);
> -
>    Flag = FilterBeforeMsrWrite (Index, &Value);
>    if (Flag) {
> +    LowData  = (UINT32)(Value);
> +    HighData = (UINT32)(Value >> 32);
>      __asm__ __volatile__ (
>        "wrmsr"
>        :
> --
> 2.31.1
> 
> 
> 
> 
> 





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