Re: [PATCH 1/1] UefiCpuPkg/MpInitLib: Always initialize the DoDecrement variable

["Laszlo Ersek" <lersek@redhat.com>]

On 08/18/20 15:10, Tom Lendacky wrote:
> From: Tom Lendacky <thomas.lendacky@amd.com>
> 
> REF: https://bugzilla.tianocore.org/show_bug.cgi?id=2901
> 
> The DoDecrement variable in ApWakeupFunction () wasn't always being
> initialized. Update the code to always fully initialize it.
> 
> Cc: Eric Dong <eric.dong@intel.com>
> Cc: Ray Ni <ray.ni@intel.com>
> Cc: Laszlo Ersek <lersek@redhat.com>
> Cc: Rahul Kumar <rahul1.kumar@intel.com>
> Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com>
> ---
>  UefiCpuPkg/Library/MpInitLib/MpLib.c | 4 +---
>  1 file changed, 1 insertion(+), 3 deletions(-)
> 
> diff --git a/UefiCpuPkg/Library/MpInitLib/MpLib.c b/UefiCpuPkg/Library/MpInitLib/MpLib.c
> index 90416c81b616..e24bdc64f930 100644
> --- a/UefiCpuPkg/Library/MpInitLib/MpLib.c
> +++ b/UefiCpuPkg/Library/MpInitLib/MpLib.c
> @@ -885,9 +885,7 @@ ApWakeupFunction (
>            UINT64                    Status;
>            BOOLEAN                   DoDecrement;
>  
> -          if (CpuMpData->InitFlag == ApInitConfig) {
> -            DoDecrement = TRUE;
> -          }
> +          DoDecrement = (CpuMpData->InitFlag == ApInitConfig) ? TRUE : FALSE;
>  
>            while (TRUE) {
>              Msr.GhcbPhysicalAddress = AsmReadMsr64 (MSR_SEV_ES_GHCB);
> 

Not that I want to obsess about style, but

  (condition) ? TRUE : FALSE

is an anti-patter that's similar to

  (condition) == TRUE

Instead, I suggest:

  DoDecrement = (BOOLEAN)(CpuMpData->InitFlag == ApInitConfig);

(The (BOOLEAN) cast is necessary, or at least used to be necessary,
becasue the == operator returns "int" (INT32), but BOOLEAN (i.e., the
type of "DoDecrement") is UINT8 -- and some VS toolchains perceive (or
used to perceive) this implicit conversion as a "potential loss of
precision". That warning is of course bogus, as the == operator only
produces 0 or 1, each of which values fits comfortably into a UINT8. But
still the explicit (BOOLEAN) cast is how we suppress the warning.)

Different question: who's supposed to merge (v2 of) this? Per
"Maintainers.txt", it should be Eric or Ray; OTOH, maybe the fix is
urgent (build failure with CLANGPDB) and anyone with push access could
qualify.

Thanks,
Laszlo