Re: [PATCH] UefiCpuPkg/PiSmmCpuDxeSmm: add message for S3 config error

[Laszlo Ersek <lersek@redhat.com>]

On 09/10/18 05:22, Jian J Wang wrote:
> BZ#: https://bugzilla.tianocore.org/show_bug.cgi?id=1165
> 
> HOB gEfiAcpiVariableGuid is a must have data for S3 resume if
> PcdAcpiS3Enable is set to TRUE. Current code in CpuS3.c doesn't
> embody this strong binding between them. An error message and
> ASSERT is added by this patch to warn platform developer about
> it.
> 
> Cc: Star Zeng <star.zeng@intel.com>
> Cc: Benjamin You <benjamin.you@intel.com>
> Cc: Eric Dong <eric.dong@intel.com>
> Cc: Laszlo Ersek <lersek@redhat.com>
> Contributed-under: TianoCore Contribution Agreement 1.1
> Signed-off-by: Jian J Wang <jian.j.wang@intel.com>
> ---
>  UefiCpuPkg/PiSmmCpuDxeSmm/CpuS3.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/UefiCpuPkg/PiSmmCpuDxeSmm/CpuS3.c b/UefiCpuPkg/PiSmmCpuDxeSmm/CpuS3.c
> index abd8a5a07b..f371667c44 100644
> --- a/UefiCpuPkg/PiSmmCpuDxeSmm/CpuS3.c
> +++ b/UefiCpuPkg/PiSmmCpuDxeSmm/CpuS3.c
> @@ -744,6 +744,9 @@ InitSmmS3ResumeState (
>      if (sizeof (UINTN) == sizeof (UINT32)) {
>        SmmS3ResumeState->Signature = SMM_S3_RESUME_SMM_32;
>      }
> +  } else {
> +    DEBUG ((DEBUG_ERROR, "ERROR: HOB(gEfiAcpiVariableGuid) needed by S3 resume doesn't exist!\n"));
> +    ASSERT (FALSE);
>    }
>  
>    //
> 

I have some superficial comments for this patch.

(1) in case the "if" has an "else" branch, I think it's better style to
use "==" in the condition than "!=". To me,

  if (GuidHob != NULL) {
    //
    // do a bunch of stuff
    //
  } else {
    //
    // error
    //
  }

is more difficult to read than:

  if (GuidHob == NULL) {
    //
    // error
    //
  } else {
    //
    // do a bunch of stuff
    //
  }

in particular if the "bunch of stuff" includes nested "if" statements.


(2) I think the error message could be improved. I'd suggest removing
the word "ERROR", since DEBUG_ERROR already sets the error level / mask.

(3) Furthermore, I suggest not logging the name "gEfiAcpiVariableGuid"
textually, as a string -- in edk2 we generally log GUIDs by value, and
log parsers / translators usually look for GUID values. Thus I suggest
using %g with &gEfiAcpiVariableGuid.

(4) Please consider logging the module name and/or the function name
too, with "%a", and gEfiCallerBaseName and/or __FUNCTION__.
"gEfiCallerBaseName" is usually only helpful with libraries (because
they can be linked into multiple drivers), but __FUNCTION__ is more
frequently helpful.

Thanks
Laszlo