Re: [PATCH] UefiCpuPkg/CpuExceptionHandlerLib: Code optimization to allow bigger stack

["Ni, Ray" <ray.ni@intel.com>]

Reviewed-by: Ray Ni <ray.ni@intel.com>

> -----Original Message-----
> From: Tan, Dun <dun.tan@intel.com>
> Sent: Wednesday, September 28, 2022 9:52 AM
> To: devel@edk2.groups.io
> Cc: Dong, Eric <eric.dong@intel.com>; Ni, Ray <ray.ni@intel.com>; Kumar,
> Rahul R <rahul.r.kumar@intel.com>
> Subject: [PATCH] UefiCpuPkg/CpuExceptionHandlerLib: Code optimization to
> allow bigger stack
> 
> This commit is a code optimization to allow bigger seperate stack size in
> ArchSetupExceptionStack. In previous code logic, CPU_STACK_ALIGNMENT
> bytes
> will be wasted if StackTop is already CPU_STACK_ALIGNMENT aligned.
> 
> Signed-off-by: Dun Tan <dun.tan@intel.com>
> Cc: Eric Dong <eric.dong@intel.com>
> Cc: Ray Ni <ray.ni@intel.com>
> Cc: Rahul Kumar <rahul1.kumar@intel.com>
> ---
>  UefiCpuPkg/Library/CpuExceptionHandlerLib/Ia32/ArchExceptionHandler.c |
> 2 +-
>  UefiCpuPkg/Library/CpuExceptionHandlerLib/X64/ArchExceptionHandler.c  |
> 2 +-
>  2 files changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git
> a/UefiCpuPkg/Library/CpuExceptionHandlerLib/Ia32/ArchExceptionHandler.c
> b/UefiCpuPkg/Library/CpuExceptionHandlerLib/Ia32/ArchExceptionHandler.
> c
> index 8c398ebc5b..c8fa30a32f 100644
> ---
> a/UefiCpuPkg/Library/CpuExceptionHandlerLib/Ia32/ArchExceptionHandler.c
> +++
> b/UefiCpuPkg/Library/CpuExceptionHandlerLib/Ia32/ArchExceptionHandler.
> c
> @@ -215,7 +215,7 @@ ArchSetupExceptionStack (
>    // Fixup exception task descriptor and task-state segment
>    //
>    AsmGetTssTemplateMap (&TemplateMap);
> -  StackTop = StackTop - CPU_STACK_ALIGNMENT;
> +  StackTop = StackTop - CPU_STACK_ALIGNMENT + 1;
>    StackTop = (UINTN)ALIGN_POINTER (StackTop, CPU_STACK_ALIGNMENT);
>    IdtTable = (IA32_IDT_GATE_DESCRIPTOR  *)Idtr.Base;
>    for (Index = 0; Index < CPU_STACK_SWITCH_EXCEPTION_NUMBER;
> ++Index) {
> diff --git
> a/UefiCpuPkg/Library/CpuExceptionHandlerLib/X64/ArchExceptionHandler.c
> b/UefiCpuPkg/Library/CpuExceptionHandlerLib/X64/ArchExceptionHandler.c
> index 80e9f08e5b..74b2193cb0 100644
> ---
> a/UefiCpuPkg/Library/CpuExceptionHandlerLib/X64/ArchExceptionHandler.c
> +++
> b/UefiCpuPkg/Library/CpuExceptionHandlerLib/X64/ArchExceptionHandler.c
> @@ -223,7 +223,7 @@ ArchSetupExceptionStack (
>    // Fixup exception task descriptor and task-state segment
>    //
>    ZeroMem (Tss, sizeof (*Tss));
> -  StackTop = StackTop - CPU_STACK_ALIGNMENT;
> +  StackTop = StackTop - CPU_STACK_ALIGNMENT + 1;
>    StackTop = (UINTN)ALIGN_POINTER (StackTop, CPU_STACK_ALIGNMENT);
>    IdtTable = (IA32_IDT_GATE_DESCRIPTOR  *)Idtr.Base;
>    for (Index = 0; Index < CPU_STACK_SWITCH_EXCEPTION_NUMBER;
> ++Index) {
> --
> 2.31.1.windows.1