Chasel,
With your changes, the flow is like:
1. check revision of loaded microcode, go to Done if it's not zero
2. find first matching microcode
3. check revision of loaded microcode, go to Done if it equals to the matching 
one
4. load the matching microcode
Done: return fail/success depending on whether the revision of loaded microcode 
is zero

I guess the step #3 is unnecessary because step #1 guarantees that step #3 
would not go to Done.
Can you please confirm? 


> -----Original Message-----
> From: devel@edk2.groups.io <devel@edk2.groups.io> On Behalf Of Chiu,
> Chasel
> Sent: Saturday, April 1, 2023 6:57 AM
> To: devel@edk2.groups.io
> Cc: Chiu, Chasel <chasel.c...@intel.com>; Desimone, Nathaniel L
> <nathaniel.l.desim...@intel.com>; Zeng, Star <star.z...@intel.com>; Ni,
> Ray <ray...@intel.com>
> Subject: [edk2-devel] [PATCH v3] IntelFsp2Pkg: LoadMicrocodeDefault()
> causing unnecessary delay.
> 
> REF: https://bugzilla.tianocore.org/show_bug.cgi?id=4391
> 
> FSP should support the scenario that CPU microcode already loaded
> before calling LoadMicrocodeDefault(), in this case it should return
> directly without spending more time.
> Also the LoadMicrocodeDefault() should only attempt to load one version
> of the microcode for current CPU and return directly without parsing
> rest of the microcode in FV.
> 
> Cc: Nate DeSimone <nathaniel.l.desim...@intel.com>
> Cc: Star Zeng <star.z...@intel.com>
> Cc: Ray Ni <ray...@intel.com>
> Signed-off-by: Chasel Chiu <chasel.c...@intel.com>
> ---
>  IntelFsp2Pkg/FspSecCore/Ia32/FspApiEntryT.nasm | 26
> ++++++++++++++++++++++----
>  IntelFsp2Pkg/FspSecCore/X64/FspApiEntryT.nasm  | 26
> ++++++++++++++++++++++----
>  2 files changed, 44 insertions(+), 8 deletions(-)
> 
> diff --git a/IntelFsp2Pkg/FspSecCore/Ia32/FspApiEntryT.nasm
> b/IntelFsp2Pkg/FspSecCore/Ia32/FspApiEntryT.nasm
> index 2cff8b3643..79f2a20a2c 100644
> --- a/IntelFsp2Pkg/FspSecCore/Ia32/FspApiEntryT.nasm
> +++ b/IntelFsp2Pkg/FspSecCore/Ia32/FspApiEntryT.nasm
> @@ -245,6 +245,22 @@ ASM_PFX(LoadMicrocodeDefault):
>     cmp    esp, 0
> 
>     jz     ParamError
> 
> 
> 
> +   ;
> 
> +   ; If microcode already loaded before this function, exit this function 
> with
> SUCCESS.
> 
> +   ;
> 
> +   mov   ecx, MSR_IA32_BIOS_SIGN_ID
> 
> +   xor   eax, eax               ; Clear EAX
> 
> +   xor   edx, edx               ; Clear EDX
> 
> +   wrmsr                        ; Load 0 to MSR at 8Bh
> 
> +
> 
> +   mov   eax, 1
> 
> +   cpuid
> 
> +   mov   ecx, MSR_IA32_BIOS_SIGN_ID
> 
> +   rdmsr                         ; Get current microcode signature
> 
> +   xor   eax, eax
> 
> +   test  edx, edx
> 
> +   jnz   Exit2
> 
> +
> 
>     ; skip loading Microcode if the MicrocodeCodeSize is zero
> 
>     ; and report error if size is less than 2k
> 
>     ; first check UPD header revision
> 
> @@ -450,7 +466,7 @@ LoadCheck:
> 
> 
>     ; Verify this microcode update is not already loaded
> 
>     cmp   dword [esi + MicrocodeHdr.MicrocodeHdrRevision], edx
> 
> -   je    Continue
> 
> +   je    Done ; if already one version microcode loaded, go to done
> 
> 
> 
>  LoadMicrocode:
> 
>     ; EAX contains the linear address of the start of the Update Data
> 
> @@ -465,10 +481,12 @@ LoadMicrocode:
>     mov   eax, 1
> 
>     cpuid
> 
> 
> 
> -Continue:
> 
> -   jmp   NextMicrocode
> 
> -
> 
>  Done:
> 
> +   mov   ecx, MSR_IA32_BIOS_SIGN_ID
> 
> +   xor   eax, eax               ; Clear EAX
> 
> +   xor   edx, edx               ; Clear EDX
> 
> +   wrmsr                        ; Load 0 to MSR at 8Bh
> 
> +
> 
>     mov   eax, 1
> 
>     cpuid
> 
>     mov   ecx, MSR_IA32_BIOS_SIGN_ID
> 
> diff --git a/IntelFsp2Pkg/FspSecCore/X64/FspApiEntryT.nasm
> b/IntelFsp2Pkg/FspSecCore/X64/FspApiEntryT.nasm
> index b32fa32a89..3e40678f47 100644
> --- a/IntelFsp2Pkg/FspSecCore/X64/FspApiEntryT.nasm
> +++ b/IntelFsp2Pkg/FspSecCore/X64/FspApiEntryT.nasm
> @@ -141,6 +141,22 @@ ASM_PFX(LoadMicrocodeDefault):
>     jz     ParamError
> 
>     mov    rsp, rcx
> 
> 
> 
> +   ;
> 
> +   ; If microcode already loaded before this function, exit this function 
> with
> SUCCESS.
> 
> +   ;
> 
> +   mov   ecx, MSR_IA32_BIOS_SIGN_ID
> 
> +   xor   eax, eax               ; Clear EAX
> 
> +   xor   edx, edx               ; Clear EDX
> 
> +   wrmsr                        ; Load 0 to MSR at 8Bh
> 
> +
> 
> +   mov   eax, 1
> 
> +   cpuid
> 
> +   mov   ecx, MSR_IA32_BIOS_SIGN_ID
> 
> +   rdmsr                         ; Get current microcode signature
> 
> +   xor   rax, rax
> 
> +   test  edx, edx
> 
> +   jnz   Exit2
> 
> +
> 
>     ; skip loading Microcode if the MicrocodeCodeSize is zero
> 
>     ; and report error if size is less than 2k
> 
>     ; first check UPD header revision
> 
> @@ -291,7 +307,7 @@ LoadCheck:
> 
> 
>     ; Verify this microcode update is not already loaded
> 
>     cmp   dword [esi + MicrocodeHdr.MicrocodeHdrRevision], edx
> 
> -   je    Continue
> 
> +   je    Done ; if already one version microcode loaded, go to done
> 
> 
> 
>  LoadMicrocode:
> 
>     ; EAX contains the linear address of the start of the Update Data
> 
> @@ -306,10 +322,12 @@ LoadMicrocode:
>     mov   eax, 1
> 
>     cpuid
> 
> 
> 
> -Continue:
> 
> -   jmp   NextMicrocode
> 
> -
> 
>  Done:
> 
> +   mov   ecx, MSR_IA32_BIOS_SIGN_ID
> 
> +   xor   eax, eax               ; Clear EAX
> 
> +   xor   edx, edx               ; Clear EDX
> 
> +   wrmsr                        ; Load 0 to MSR at 8Bh
> 
> +
> 
>     mov   eax, 1
> 
>     cpuid
> 
>     mov   ecx, MSR_IA32_BIOS_SIGN_ID
> 
> --
> 2.35.0.windows.1
> 
> 
> 
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