OvmfPkg/ResetVector: split SEV and non-CoCo workflows

Use separate control flows for SEV and non-CoCo cases.

SevClearPageEncMaskForGhcbPage and GetSevCBitMaskAbove31 will now only
be called when running in SEV mode, so the SEV check in these functions
is not needed any more.

No functional change.

Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
Reviewed-by: Laszlo Ersek <lersek@redhat.com>
Message-Id: <20240301074402.98625-6-kraxel@redhat.com>
Cc: Jiewen Yao <jiewen.yao@intel.com>
Cc: Oliver Steffen <osteffen@redhat.com>
Cc: Michael Roth <michael.roth@amd.com>
Cc: Erdem Aktas <erdemaktas@google.com>
Cc: Min Xu <min.m.xu@intel.com>
Cc: Ard Biesheuvel <ardb+tianocore@kernel.org>
Cc: Tom Lendacky <thomas.lendacky@amd.com>
[lersek@redhat.com: turn the "Cc:" message headers from Gerd's on-list
 posting into "Cc:" tags in the commit message, in order to pacify
 "PatchCheck.py"]

OvmfPkg/ResetVector/Ia32/PageTables64.asm

@@ -118,15 +118,26 @@ SetCr3ForPageTables64:
 
     ; Check whether the SEV is active and populate the SevEsWorkArea
     OneTimeCall   CheckSevFeatures
+    cmp       byte[WORK_AREA_GUEST_TYPE], 1
+    jz        SevInit
 
+    ;
+    ; normal (non-CoCo) workflow
+    ;
+    ClearOvmfPageTables
+    CreatePageTables4Level 0
+    jmp SetCr3
+
+SevInit:
+    ;
+    ; SEV workflow
+    ;
+    ClearOvmfPageTables
     ; If SEV is enabled, the C-bit position is always above 31.
     ; The mask will be saved in the EDX and applied during the
     ; the page table build below.
     OneTimeCall   GetSevCBitMaskAbove31
-
-    ClearOvmfPageTables
     CreatePageTables4Level edx
-
     ; Clear the C-bit from the GHCB page if the SEV-ES is enabled.
     OneTimeCall   SevClearPageEncMaskForGhcbPage
     jmp SetCr3