diff --git a/UefiCpuPkg/Library/MpInitLib/DxeMpInitLib.inf b/UefiCpuPkg/Library/MpInitLib/DxeMpInitLib.inf
index 37b3f64e57..cd912ab0c5 100644
--- a/UefiCpuPkg/Library/MpInitLib/DxeMpInitLib.inf
+++ b/UefiCpuPkg/Library/MpInitLib/DxeMpInitLib.inf
@@ -61,6 +61,7 @@
 
 [Pcd]
   gUefiCpuPkgTokenSpaceGuid.PcdCpuMaxLogicalProcessorNumber        ## CONSUMES
+  gUefiCpuPkgTokenSpaceGuid.PcdCpuBootLogicalProcessorNumber       ## CONSUMES
   gUefiCpuPkgTokenSpaceGuid.PcdCpuApInitTimeOutInMicroSeconds      ## SOMETIMES_CONSUMES
   gUefiCpuPkgTokenSpaceGuid.PcdCpuApStackSize                      ## CONSUMES
   gUefiCpuPkgTokenSpaceGuid.PcdCpuMicrocodePatchAddress            ## CONSUMES
diff --git a/UefiCpuPkg/Library/MpInitLib/MpLib.c b/UefiCpuPkg/Library/MpInitLib/MpLib.c
index 594a035d8b..622b70ca3c 100644
--- a/UefiCpuPkg/Library/MpInitLib/MpLib.c
+++ b/UefiCpuPkg/Library/MpInitLib/MpLib.c
@@ -1044,46 +1044,67 @@ WakeUpAP (
       SendInitSipiSipiAllExcludingSelf ((UINT32) ExchangeInfo->BufferStart);
     }
     if (CpuMpData->InitFlag == ApInitConfig) {
-      //
-      // The AP enumeration algorithm below is suitable for two use cases.
-      //
-      // (1) The check-in time for an individual AP is bounded, and APs run
-      //     through their initialization routines strongly concurrently. In
-      //     particular, the number of concurrently running APs
-      //     ("NumApsExecuting") is never expected to fall to zero
-      //     *temporarily* -- it is expected to fall to zero only when all
-      //     APs have checked-in.
-      //
-      //     In this case, the platform is supposed to set
-      //     PcdCpuApInitTimeOutInMicroSeconds to a low-ish value (just long
-      //     enough for one AP to start initialization). The timeout will be
-      //     reached soon, and remaining APs are collected by watching
-      //     NumApsExecuting fall to zero. If NumApsExecuting falls to zero
-      //     mid-process, while some APs have not completed initialization,
-      //     the behavior is undefined.
-      //
-      // (2) The check-in time for an individual AP is unbounded, and/or APs
-      //     may complete their initializations widely spread out. In
-      //     particular, some APs may finish initialization before some APs
-      //     even start.
-      //
-      //     In this case, the platform is supposed to set
-      //     PcdCpuApInitTimeOutInMicroSeconds to a high-ish value. The AP
-      //     enumeration will always take that long (except when the boot CPU
-      //     count happens to be maximal, that is,
-      //     PcdCpuMaxLogicalProcessorNumber). All APs are expected to
-      //     check-in before the timeout, and NumApsExecuting is assumed zero
-      //     at timeout. APs that miss the time-out may cause undefined
-      //     behavior.
-      //
-      TimedWaitForApFinish (
-        CpuMpData,
-        PcdGet32 (PcdCpuMaxLogicalProcessorNumber) - 1,
-        PcdGet32 (PcdCpuApInitTimeOutInMicroSeconds)
-        );
+      if (PcdGet32 (PcdCpuBootLogicalProcessorNumber) > 0) {
+        //
+        // The AP enumeration algorithm below is suitable only when the
+        // platform can tell us the *exact* boot CPU count in advance.
+        //
+        // The wait below finishes only when the detected AP count reaches
+        // (PcdCpuBootLogicalProcessorNumber - 1), regardless of how long that
+        // takes. If at least one AP fails to check in (meaning a platform
+        // hardware bug), the detection hangs forever, by design. If the actual
+        // boot CPU count in the system is higher than
+        // PcdCpuBootLogicalProcessorNumber (meaning a platform
+        // misconfiguration), then some APs may complete initialization after
+        // the wait finishes, and cause undefined behavior.
+        //
+        TimedWaitForApFinish (
+          CpuMpData,
+          PcdGet32 (PcdCpuBootLogicalProcessorNumber) - 1,
+          MAX_UINT32 // approx. 71 minutes
+          );
+      } else {
+        //
+        // The AP enumeration algorithm below is suitable for two use cases.
+        //
+        // (1) The check-in time for an individual AP is bounded, and APs run
+        //     through their initialization routines strongly concurrently. In
+        //     particular, the number of concurrently running APs
+        //     ("NumApsExecuting") is never expected to fall to zero
+        //     *temporarily* -- it is expected to fall to zero only when all
+        //     APs have checked-in.
+        //
+        //     In this case, the platform is supposed to set
+        //     PcdCpuApInitTimeOutInMicroSeconds to a low-ish value (just long
+        //     enough for one AP to start initialization). The timeout will be
+        //     reached soon, and remaining APs are collected by watching
+        //     NumApsExecuting fall to zero. If NumApsExecuting falls to zero
+        //     mid-process, while some APs have not completed initialization,
+        //     the behavior is undefined.
+        //
+        // (2) The check-in time for an individual AP is unbounded, and/or APs
+        //     may complete their initializations widely spread out. In
+        //     particular, some APs may finish initialization before some APs
+        //     even start.
+        //
+        //     In this case, the platform is supposed to set
+        //     PcdCpuApInitTimeOutInMicroSeconds to a high-ish value. The AP
+        //     enumeration will always take that long (except when the boot CPU
+        //     count happens to be maximal, that is,
+        //     PcdCpuMaxLogicalProcessorNumber). All APs are expected to
+        //     check-in before the timeout, and NumApsExecuting is assumed zero
+        //     at timeout. APs that miss the time-out may cause undefined
+        //     behavior.
+        //
+        TimedWaitForApFinish (
+          CpuMpData,
+          PcdGet32 (PcdCpuMaxLogicalProcessorNumber) - 1,
+          PcdGet32 (PcdCpuApInitTimeOutInMicroSeconds)
+          );
 
-      while (CpuMpData->MpCpuExchangeInfo->NumApsExecuting != 0) {
-        CpuPause();
+        while (CpuMpData->MpCpuExchangeInfo->NumApsExecuting != 0) {
+          CpuPause();
+        }
       }
     } else {
       //
diff --git a/UefiCpuPkg/Library/MpInitLib/PeiMpInitLib.inf b/UefiCpuPkg/Library/MpInitLib/PeiMpInitLib.inf
index 82b77b63ea..1538185ef9 100644
--- a/UefiCpuPkg/Library/MpInitLib/PeiMpInitLib.inf
+++ b/UefiCpuPkg/Library/MpInitLib/PeiMpInitLib.inf
@@ -53,7 +53,8 @@
 
 [Pcd]
   gUefiCpuPkgTokenSpaceGuid.PcdCpuMaxLogicalProcessorNumber        ## CONSUMES
-  gUefiCpuPkgTokenSpaceGuid.PcdCpuApInitTimeOutInMicroSeconds      ## CONSUMES
+  gUefiCpuPkgTokenSpaceGuid.PcdCpuBootLogicalProcessorNumber       ## CONSUMES
+  gUefiCpuPkgTokenSpaceGuid.PcdCpuApInitTimeOutInMicroSeconds      ## SOMETIMES_CONSUMES
   gUefiCpuPkgTokenSpaceGuid.PcdCpuApStackSize                      ## CONSUMES
   gUefiCpuPkgTokenSpaceGuid.PcdCpuMicrocodePatchAddress            ## CONSUMES
   gUefiCpuPkgTokenSpaceGuid.PcdCpuMicrocodePatchRegionSize         ## CONSUMES
diff --git a/UefiCpuPkg/UefiCpuPkg.dec b/UefiCpuPkg/UefiCpuPkg.dec
index 031a2ccd68..12f4413ea5 100644
--- a/UefiCpuPkg/UefiCpuPkg.dec
+++ b/UefiCpuPkg/UefiCpuPkg.dec
@@ -227,6 +227,19 @@
   ## Specifies timeout value in microseconds for the BSP to detect all APs for the first time.
   # @Prompt Timeout for the BSP to detect all APs for the first time.
   gUefiCpuPkgTokenSpaceGuid.PcdCpuApInitTimeOutInMicroSeconds|50000|UINT32|0x00000004
+  ## Specifies the number of Logical Processors that are available in the
+  #  preboot environment after platform reset, including BSP and APs. Possible
+  #  values:<BR><BR>
+  #  zero (default) - PcdCpuBootLogicalProcessorNumber is ignored, and
+  #                   PcdCpuApInitTimeOutInMicroSeconds limits the initial AP
+  #                   detection by the BSP.<BR>
+  #  nonzero        - PcdCpuApInitTimeOutInMicroSeconds is ignored. The initial
+  #                   AP detection finishes only when the detected CPU count
+  #                   (BSP plus APs) reaches the value of
+  #                   PcdCpuBootLogicalProcessorNumber, regardless of how long
+  #                   that takes.<BR>
+  # @Prompt Number of Logical Processors available after platform reset.
+  gUefiCpuPkgTokenSpaceGuid.PcdCpuBootLogicalProcessorNumber|0|UINT32|0x00000008
   ## Specifies the base address of the first microcode Patch in the microcode Region.
   # @Prompt Microcode Region base address.
   gUefiCpuPkgTokenSpaceGuid.PcdCpuMicrocodePatchAddress|0x0|UINT64|0x00000005
diff --git a/UefiCpuPkg/UefiCpuPkg.uni b/UefiCpuPkg/UefiCpuPkg.uni
index fbf7680726..a7e279c5cb 100644
--- a/UefiCpuPkg/UefiCpuPkg.uni
+++ b/UefiCpuPkg/UefiCpuPkg.uni
@@ -37,6 +37,10 @@
 
 #string STR_gUefiCpuPkgTokenSpaceGuid_PcdCpuApInitTimeOutInMicroSeconds_HELP  #language en-US "Specifies timeout value in microseconds for the BSP to detect all APs for the first time."
 
+#string STR_gUefiCpuPkgTokenSpaceGuid_PcdCpuBootLogicalProcessorNumber_PROMPT  #language en-US "Number of Logical Processors available after platform reset."
+
+#string STR_gUefiCpuPkgTokenSpaceGuid_PcdCpuBootLogicalProcessorNumber_HELP  #language en-US "Specifies the number of Logical Processors that are available in the preboot environment after platform reset, including BSP and APs."
+
 #string STR_gUefiCpuPkgTokenSpaceGuid_PcdCpuMicrocodePatchAddress_PROMPT  #language en-US "Microcode Region base address."
 
 #string STR_gUefiCpuPkgTokenSpaceGuid_PcdCpuMicrocodePatchAddress_HELP  #language en-US "Specifies the base address of the first microcode Patch in the microcode Region."