[PATCH 1/1] UefiCpuPkg: Save PcdConfidentialComputingGuestAttr in mCcGuestAttr

["Min Xu" <min.m.xu@intel.com>]

BZ: https://bugzilla.tianocore.org/show_bug.cgi?id=3918

There is an issue reported when booting multiple vCPU guests (regular
and SEV). This issues consist of EfiAcquireLock() / EfiReleaseLock()
ASSERTS and TPL level ASSERTS that occur during ExitBootServices when
the APs are being parked by RelocateApLoop(). The root cause is that
PCD accesses use locking which is not SMP safe.

To fix this issue PCD usage can be reduced to getting the
PcdConfidentialComputingGuestAttr value at init (MpInitLibInitialize)
and caching it in a STATIC variable (mCcGuestAttr).

Cc: Brijesh Singh <brijesh.singh@amd.com>
Cc: Erdem Aktas <erdemaktas@google.com>
Cc: James Bottomley <jejb@linux.ibm.com>
Cc: Jiewen Yao <jiewen.yao@intel.com>
Cc: Tom Lendacky <thomas.lendacky@amd.com>
Cc: Eric Dong <eric.dong@intel.com>
Cc: Ray Ni <ray.ni@intel.com>
Signed-off-by: Min Xu <min.m.xu@intel.com>
---
 UefiCpuPkg/Library/MpInitLib/MpLib.c | 19 +++++++++++--------
 1 file changed, 11 insertions(+), 8 deletions(-)

diff --git a/UefiCpuPkg/Library/MpInitLib/MpLib.c b/UefiCpuPkg/Library/MpInitLib/MpLib.c
index 91c7afaeb2ad..fb9247f58427 100644
--- a/UefiCpuPkg/Library/MpInitLib/MpLib.c
+++ b/UefiCpuPkg/Library/MpInitLib/MpLib.c
@@ -16,6 +16,7 @@
 #include <ConfidentialComputingGuestAttr.h>
 
 EFI_GUID  mCpuInitMpLibHobGuid = CPU_INIT_MP_LIB_HOB_GUID;
+UINT64    mCcGuestAttr         = 0;
 
 /**
   The function will check if BSP Execute Disable is enabled.
@@ -1805,7 +1806,9 @@ MpInitLibInitialize (
   UINTN                    BackupBufferAddr;
   UINTN                    ApIdtBase;
 
-  if (CC_GUEST_IS_TDX (PcdGet64 (PcdConfidentialComputingGuestAttr))) {
+  mCcGuestAttr = PcdGet64 (PcdConfidentialComputingGuestAttr);
+
+  if (CC_GUEST_IS_TDX (mCcGuestAttr)) {
     return EFI_SUCCESS;
   }
 
@@ -2079,7 +2082,7 @@ MpInitLibGetProcessorInfo (
   CPU_INFO_IN_HOB  *CpuInfoInHob;
   UINTN            OriginalProcessorNumber;
 
-  if (CC_GUEST_IS_TDX (PcdGet64 (PcdConfidentialComputingGuestAttr))) {
+  if (CC_GUEST_IS_TDX (mCcGuestAttr)) {
     return TdxMpInitLibGetProcessorInfo (ProcessorNumber, ProcessorInfoBuffer, HealthData);
   }
 
@@ -2177,7 +2180,7 @@ SwitchBSPWorker (
   BOOLEAN                      OldInterruptState;
   BOOLEAN                      OldTimerInterruptState;
 
-  if (CC_GUEST_IS_TDX (PcdGet64 (PcdConfidentialComputingGuestAttr))) {
+  if (CC_GUEST_IS_TDX (mCcGuestAttr)) {
     return EFI_UNSUPPORTED;
   }
 
@@ -2321,7 +2324,7 @@ EnableDisableApWorker (
   CPU_MP_DATA  *CpuMpData;
   UINTN        CallerNumber;
 
-  if (CC_GUEST_IS_TDX (PcdGet64 (PcdConfidentialComputingGuestAttr))) {
+  if (CC_GUEST_IS_TDX (mCcGuestAttr)) {
     return EFI_UNSUPPORTED;
   }
 
@@ -2385,7 +2388,7 @@ MpInitLibWhoAmI (
     return EFI_INVALID_PARAMETER;
   }
 
-  if (CC_GUEST_IS_TDX (PcdGet64 (PcdConfidentialComputingGuestAttr))) {
+  if (CC_GUEST_IS_TDX (mCcGuestAttr)) {
     *ProcessorNumber = 0;
     return EFI_SUCCESS;
   }
@@ -2432,7 +2435,7 @@ MpInitLibGetNumberOfProcessors (
     return EFI_INVALID_PARAMETER;
   }
 
-  if (CC_GUEST_IS_TDX (PcdGet64 (PcdConfidentialComputingGuestAttr))) {
+  if (CC_GUEST_IS_TDX (mCcGuestAttr)) {
     return TdxMpInitLibGetNumberOfProcessors (NumberOfProcessors, NumberOfEnabledProcessors);
   }
 
@@ -2534,7 +2537,7 @@ StartupAllCPUsWorker (
     return EFI_INVALID_PARAMETER;
   }
 
-  if (CC_GUEST_IS_TDX (PcdGet64 (PcdConfidentialComputingGuestAttr))) {
+  if (CC_GUEST_IS_TDX (mCcGuestAttr)) {
     //
     // For Td guest ExcludeBsp must be FALSE. Otherwise it will return in above checks.
     //
@@ -2692,7 +2695,7 @@ StartupThisAPWorker (
   //
   // In Td guest, startup of AP is not supported in current stage.
   //
-  if (CC_GUEST_IS_TDX (PcdGet64 (PcdConfidentialComputingGuestAttr))) {
+  if (CC_GUEST_IS_TDX (mCcGuestAttr)) {
     return EFI_UNSUPPORTED;
   }
 
-- 
2.29.2.windows.2