[PATCH v2 3/3] OvmfPkg/PlatformPei: take VCPU count from QEMU and configure MpInitLib

[Laszlo Ersek <lersek@redhat.com>]

These settings will allow CpuMpPei and CpuDxe to wait for the initial AP
check-ins exactly as long as necessary.

It is safe to set PcdCpuMaxLogicalProcessorNumber and
PcdCpuApInitTimeOutInMicroSeconds in OvmfPkg/PlatformPei.
OvmfPkg/PlatformPei installs the permanent PEI RAM, producing
gEfiPeiMemoryDiscoveredPpiGuid, and UefiCpuPkg/CpuMpPei has a depex on
gEfiPeiMemoryDiscoveredPpiGuid.

It is safe to read the fw_cfg item QemuFwCfgItemSmpCpuCount (0x0005). It
was added to QEMU in 2008 as key FW_CFG_NB_CPUS, in commit 905fdcb5264c
("Add common keys to firmware configuration"). Even if the key is
unavailable (or if fw_cfg is entirely unavailable, for example on Xen),
QemuFwCfgRead16() will return 0, and then we stick with the current
behavior.

Cc: Igor Mammedov <imammedo@redhat.com>
Cc: Jeff Fan <jeff.fan@intel.com>
Cc: Jordan Justen <jordan.l.justen@intel.com>
Cc: Michael Kinney <michael.d.kinney@intel.com>
Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Laszlo Ersek <lersek@redhat.com>
---
 OvmfPkg/OvmfPkgIa32.dsc             |  4 ++
 OvmfPkg/OvmfPkgIa32X64.dsc          |  4 ++
 OvmfPkg/OvmfPkgX64.dsc              |  4 ++
 OvmfPkg/PlatformPei/PlatformPei.inf |  1 +
 OvmfPkg/PlatformPei/Platform.h      |  2 +
 OvmfPkg/PlatformPei/MemDetect.c     |  2 +-
 OvmfPkg/PlatformPei/Platform.c      | 43 ++++++++++++++++++++
 7 files changed, 59 insertions(+), 1 deletion(-)

diff --git a/OvmfPkg/OvmfPkgIa32.dsc b/OvmfPkg/OvmfPkgIa32.dsc
index ed43c4514491..d91303052263 100644
--- a/OvmfPkg/OvmfPkgIa32.dsc
+++ b/OvmfPkg/OvmfPkgIa32.dsc
@@ -488,6 +488,10 @@ [PcdsDynamicDefault]
   gEfiMdeModulePkgTokenSpaceGuid.PcdSetNxForStack|FALSE
   gEfiMdeModulePkgTokenSpaceGuid.PcdPropertiesTableEnable|FALSE
 
+  # UefiCpuPkg PCDs related to initial AP bringup and general AP management.
+  gUefiCpuPkgTokenSpaceGuid.PcdCpuMaxLogicalProcessorNumber|64
+  gUefiCpuPkgTokenSpaceGuid.PcdCpuApInitTimeOutInMicroSeconds|50000
+
 ################################################################################
 #
 # Components Section - list of all EDK II Modules needed by this Platform.
diff --git a/OvmfPkg/OvmfPkgIa32X64.dsc b/OvmfPkg/OvmfPkgIa32X64.dsc
index ccd156d9231a..8143ea9c2837 100644
--- a/OvmfPkg/OvmfPkgIa32X64.dsc
+++ b/OvmfPkg/OvmfPkgIa32X64.dsc
@@ -496,6 +496,10 @@ [PcdsDynamicDefault]
   gEfiMdeModulePkgTokenSpaceGuid.PcdSetNxForStack|FALSE
   gEfiMdeModulePkgTokenSpaceGuid.PcdPropertiesTableEnable|FALSE
 
+  # UefiCpuPkg PCDs related to initial AP bringup and general AP management.
+  gUefiCpuPkgTokenSpaceGuid.PcdCpuMaxLogicalProcessorNumber|64
+  gUefiCpuPkgTokenSpaceGuid.PcdCpuApInitTimeOutInMicroSeconds|50000
+
 ################################################################################
 #
 # Components Section - list of all EDK II Modules needed by this Platform.
diff --git a/OvmfPkg/OvmfPkgX64.dsc b/OvmfPkg/OvmfPkgX64.dsc
index 012ce85462c5..d48d603d33d4 100644
--- a/OvmfPkg/OvmfPkgX64.dsc
+++ b/OvmfPkg/OvmfPkgX64.dsc
@@ -495,6 +495,10 @@ [PcdsDynamicDefault]
   gEfiMdeModulePkgTokenSpaceGuid.PcdSetNxForStack|FALSE
   gEfiMdeModulePkgTokenSpaceGuid.PcdPropertiesTableEnable|FALSE
 
+  # UefiCpuPkg PCDs related to initial AP bringup and general AP management.
+  gUefiCpuPkgTokenSpaceGuid.PcdCpuMaxLogicalProcessorNumber|64
+  gUefiCpuPkgTokenSpaceGuid.PcdCpuApInitTimeOutInMicroSeconds|50000
+
 ################################################################################
 #
 # Components Section - list of all EDK II Modules needed by this Platform.
diff --git a/OvmfPkg/PlatformPei/PlatformPei.inf b/OvmfPkg/PlatformPei/PlatformPei.inf
index 776a4ab11f79..fbaed3182dcf 100644
--- a/OvmfPkg/PlatformPei/PlatformPei.inf
+++ b/OvmfPkg/PlatformPei/PlatformPei.inf
@@ -95,6 +95,7 @@ [Pcd]
   gEfiMdeModulePkgTokenSpaceGuid.PcdAcpiS3Enable
   gUefiCpuPkgTokenSpaceGuid.PcdCpuLocalApicBaseAddress
   gUefiCpuPkgTokenSpaceGuid.PcdCpuMaxLogicalProcessorNumber
+  gUefiCpuPkgTokenSpaceGuid.PcdCpuApInitTimeOutInMicroSeconds
   gUefiCpuPkgTokenSpaceGuid.PcdCpuApStackSize
 
 [FixedPcd]
diff --git a/OvmfPkg/PlatformPei/Platform.h b/OvmfPkg/PlatformPei/Platform.h
index eda765be30de..18f42c3f0ea8 100644
--- a/OvmfPkg/PlatformPei/Platform.h
+++ b/OvmfPkg/PlatformPei/Platform.h
@@ -101,4 +101,6 @@ extern BOOLEAN mS3Supported;
 
 extern UINT8 mPhysMemAddressWidth;
 
+extern UINT32 mMaxCpuCount;
+
 #endif // _PLATFORM_PEI_H_INCLUDED_
diff --git a/OvmfPkg/PlatformPei/MemDetect.c b/OvmfPkg/PlatformPei/MemDetect.c
index d00a570d4381..af96a04d194a 100644
--- a/OvmfPkg/PlatformPei/MemDetect.c
+++ b/OvmfPkg/PlatformPei/MemDetect.c
@@ -358,7 +358,7 @@ PublishPeiMemory (
   //
   if (mS3Supported) {
     mS3AcpiReservedMemorySize = SIZE_512KB +
-      PcdGet32 (PcdCpuMaxLogicalProcessorNumber) *
+      mMaxCpuCount *
       PcdGet32 (PcdCpuApStackSize);
     mS3AcpiReservedMemoryBase = LowerMemorySize - mS3AcpiReservedMemorySize;
     LowerMemorySize = mS3AcpiReservedMemoryBase;
diff --git a/OvmfPkg/PlatformPei/Platform.c b/OvmfPkg/PlatformPei/Platform.c
index c6e1106c9ed0..8522fe5d831d 100644
--- a/OvmfPkg/PlatformPei/Platform.c
+++ b/OvmfPkg/PlatformPei/Platform.c
@@ -68,6 +68,7 @@ EFI_BOOT_MODE mBootMode = BOOT_WITH_FULL_CONFIGURATION;
 
 BOOLEAN mS3Supported = FALSE;
 
+UINT32 mMaxCpuCount;
 
 VOID
 AddIoMemoryBaseSizeHob (
@@ -568,6 +569,47 @@ S3Verification (
 
 
 /**
+  Fetch the number of boot CPUs from QEMU and expose it to UefiCpuPkg modules.
+  Set the mMaxCpuCount variable.
+**/
+VOID
+MaxCpuCountInitialization (
+  VOID
+  )
+{
+  UINT16        ProcessorCount;
+  RETURN_STATUS PcdStatus;
+
+  QemuFwCfgSelectItem (QemuFwCfgItemSmpCpuCount);
+  ProcessorCount = QemuFwCfgRead16 ();
+  //
+  // If the fw_cfg key or fw_cfg entirely is unavailable, load mMaxCpuCount
+  // from the PCD default. No change to PCDs.
+  //
+  if (ProcessorCount == 0) {
+    mMaxCpuCount = PcdGet32 (PcdCpuMaxLogicalProcessorNumber);
+    return;
+  }
+  //
+  // Otherwise, set mMaxCpuCount to the value reported by QEMU.
+  //
+  mMaxCpuCount = ProcessorCount;
+  //
+  // Additionally, tell UefiCpuPkg modules (a) the exact number of VCPUs, (b)
+  // to wait, in the initial AP bringup, exactly as long as it takes for all of
+  // the APs to report in. For this, we set an infinite timeout (represented by
+  // 0 microseconds).
+  //
+  PcdStatus = PcdSet32S (PcdCpuMaxLogicalProcessorNumber, ProcessorCount);
+  ASSERT_RETURN_ERROR (PcdStatus);
+  PcdStatus = PcdSet32S (PcdCpuApInitTimeOutInMicroSeconds, 0);
+  ASSERT_RETURN_ERROR (PcdStatus);
+  DEBUG ((DEBUG_INFO, "%a: QEMU reports %d processor(s)\n", __FUNCTION__,
+    ProcessorCount));
+}
+
+
+/**
   Perform Platform PEI initialization.
 
   @param  FileHandle      Handle of the file being invoked.
@@ -601,6 +643,7 @@ InitializePlatform (
   S3Verification ();
   BootModeInitialization ();
   AddressWidthInitialization ();
+  MaxCpuCountInitialization ();
 
   PublishPeiMemory ();
 
-- 
2.9.2