[PATCH v2 07/16] OvmfPkg/CpuHotplugSmm: add hotplug register block helper functions

["Laszlo Ersek" <lersek@redhat.com>]

Add a handful of simple functions for accessing QEMU's hotplug registers
more conveniently. These functions thinly wrap some of the registers
described in "docs/specs/acpi_cpu_hotplug.txt" in the QEMU tree. The
functions hang (by design) if they encounter an internal failure.

Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc: Igor Mammedov <imammedo@redhat.com>
Cc: Jiewen Yao <jiewen.yao@intel.com>
Cc: Jordan Justen <jordan.l.justen@intel.com>
Cc: Michael Kinney <michael.d.kinney@intel.com>
Cc: Philippe Mathieu-Daudé <philmd@redhat.com>
Ref: https://bugzilla.tianocore.org/show_bug.cgi?id=1512
Signed-off-by: Laszlo Ersek <lersek@redhat.com>
Acked-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
---

Notes:
    v2:
    
    - Pick up Ard's Acked-by, which is conditional on approval from Intel
      reviewers on Cc. (I'd like to save Ard the churn of re-acking
      unmodified patches.)

 OvmfPkg/CpuHotplugSmm/CpuHotplugSmm.inf |   2 +
 OvmfPkg/CpuHotplugSmm/QemuCpuhp.h       |  47 +++++++
 OvmfPkg/CpuHotplugSmm/QemuCpuhp.c       | 136 ++++++++++++++++++++
 3 files changed, 185 insertions(+)

diff --git a/OvmfPkg/CpuHotplugSmm/CpuHotplugSmm.inf b/OvmfPkg/CpuHotplugSmm/CpuHotplugSmm.inf
index fa70858a8dab..ac4ca4c1f4f2 100644
--- a/OvmfPkg/CpuHotplugSmm/CpuHotplugSmm.inf
+++ b/OvmfPkg/CpuHotplugSmm/CpuHotplugSmm.inf
@@ -4,44 +4,46 @@
 # Copyright (c) 2020, Red Hat, Inc.
 #
 # SPDX-License-Identifier: BSD-2-Clause-Patent
 ##
 
 [Defines]
   INF_VERSION                = 1.29
   PI_SPECIFICATION_VERSION   = 0x00010046                            # PI-1.7.0
   BASE_NAME                  = CpuHotplugSmm
   FILE_GUID                  = 84EEA114-C6BE-4445-8F90-51D97863E363
   MODULE_TYPE                = DXE_SMM_DRIVER
   ENTRY_POINT                = CpuHotplugEntry
 
 #
 # The following information is for reference only and not required by the build
 # tools.
 #
 # VALID_ARCHITECTURES        = IA32 X64
 #
 
 [Sources]
   CpuHotplug.c
+  QemuCpuhp.c
+  QemuCpuhp.h
 
 [Packages]
   MdePkg/MdePkg.dec
   OvmfPkg/OvmfPkg.dec
 
 [LibraryClasses]
   BaseLib
   DebugLib
   MmServicesTableLib
   PcdLib
   UefiDriverEntryPoint
 
 [Protocols]
   gEfiMmCpuIoProtocolGuid                                           ## CONSUMES
 
 [Pcd]
   gUefiOvmfPkgTokenSpaceGuid.PcdQ35SmramAtDefaultSmbase             ## CONSUMES
 
 [FeaturePcd]
   gUefiOvmfPkgTokenSpaceGuid.PcdSmmSmramRequire                     ## CONSUMES
 
 [Depex]
diff --git a/OvmfPkg/CpuHotplugSmm/QemuCpuhp.h b/OvmfPkg/CpuHotplugSmm/QemuCpuhp.h
new file mode 100644
index 000000000000..82f88f0b73bb
--- /dev/null
+++ b/OvmfPkg/CpuHotplugSmm/QemuCpuhp.h
@@ -0,0 +1,47 @@
+/** @file
+  Simple wrapper functions that access QEMU's modern CPU hotplug register
+  block.
+
+  These functions thinly wrap some of the registers described in
+  "docs/specs/acpi_cpu_hotplug.txt" in the QEMU source. IO Ports are accessed
+  via EFI_MM_CPU_IO_PROTOCOL. If a protocol call fails, these functions don't
+  return.
+
+  Copyright (c) 2020, Red Hat, Inc.
+
+  SPDX-License-Identifier: BSD-2-Clause-Patent
+**/
+
+#ifndef QEMU_CPUHP_H_
+#define QEMU_CPUHP_H_
+
+#include <Protocol/MmCpuIo.h>  // EFI_MM_CPU_IO_PROTOCOL
+
+UINT32
+QemuCpuhpReadCommandData2 (
+  IN CONST EFI_MM_CPU_IO_PROTOCOL *MmCpuIo
+  );
+
+UINT8
+QemuCpuhpReadCpuStatus (
+  IN CONST EFI_MM_CPU_IO_PROTOCOL *MmCpuIo
+  );
+
+UINT32
+QemuCpuhpReadCommandData (
+  IN CONST EFI_MM_CPU_IO_PROTOCOL *MmCpuIo
+  );
+
+VOID
+QemuCpuhpWriteCpuSelector (
+  IN CONST EFI_MM_CPU_IO_PROTOCOL *MmCpuIo,
+  IN UINT32                       Selector
+  );
+
+VOID
+QemuCpuhpWriteCommand (
+  IN CONST EFI_MM_CPU_IO_PROTOCOL *MmCpuIo,
+  IN UINT8                        Command
+  );
+
+#endif // QEMU_CPUHP_H_
diff --git a/OvmfPkg/CpuHotplugSmm/QemuCpuhp.c b/OvmfPkg/CpuHotplugSmm/QemuCpuhp.c
new file mode 100644
index 000000000000..31e46f51934a
--- /dev/null
+++ b/OvmfPkg/CpuHotplugSmm/QemuCpuhp.c
@@ -0,0 +1,136 @@
+/** @file
+  Simple wrapper functions that access QEMU's modern CPU hotplug register
+  block.
+
+  These functions thinly wrap some of the registers described in
+  "docs/specs/acpi_cpu_hotplug.txt" in the QEMU source. IO Ports are accessed
+  via EFI_MM_CPU_IO_PROTOCOL. If a protocol call fails, these functions don't
+  return.
+
+  Copyright (c) 2020, Red Hat, Inc.
+
+  SPDX-License-Identifier: BSD-2-Clause-Patent
+**/
+
+#include <IndustryStandard/Q35MchIch9.h>     // ICH9_CPU_HOTPLUG_BASE
+#include <IndustryStandard/QemuCpuHotplug.h> // QEMU_CPUHP_R_CMD_DATA2
+#include <Library/BaseLib.h>                 // CpuDeadLoop()
+#include <Library/DebugLib.h>                // DEBUG()
+
+#include "QemuCpuhp.h"
+
+UINT32
+QemuCpuhpReadCommandData2 (
+  IN CONST EFI_MM_CPU_IO_PROTOCOL *MmCpuIo
+  )
+{
+  UINT32     CommandData2;
+  EFI_STATUS Status;
+
+  CommandData2 = 0;
+  Status = MmCpuIo->Io.Read (
+                         MmCpuIo,
+                         MM_IO_UINT32,
+                         ICH9_CPU_HOTPLUG_BASE + QEMU_CPUHP_R_CMD_DATA2,
+                         1,
+                         &CommandData2
+                         );
+  if (EFI_ERROR (Status)) {
+    DEBUG ((DEBUG_ERROR, "%a: %r\n", __FUNCTION__, Status));
+    ASSERT (FALSE);
+    CpuDeadLoop ();
+  }
+  return CommandData2;
+}
+
+UINT8
+QemuCpuhpReadCpuStatus (
+  IN CONST EFI_MM_CPU_IO_PROTOCOL *MmCpuIo
+  )
+{
+  UINT8      CpuStatus;
+  EFI_STATUS Status;
+
+  CpuStatus = 0;
+  Status = MmCpuIo->Io.Read (
+                         MmCpuIo,
+                         MM_IO_UINT8,
+                         ICH9_CPU_HOTPLUG_BASE + QEMU_CPUHP_R_CPU_STAT,
+                         1,
+                         &CpuStatus
+                         );
+  if (EFI_ERROR (Status)) {
+    DEBUG ((DEBUG_ERROR, "%a: %r\n", __FUNCTION__, Status));
+    ASSERT (FALSE);
+    CpuDeadLoop ();
+  }
+  return CpuStatus;
+}
+
+UINT32
+QemuCpuhpReadCommandData (
+  IN CONST EFI_MM_CPU_IO_PROTOCOL *MmCpuIo
+  )
+{
+  UINT32     CommandData;
+  EFI_STATUS Status;
+
+  CommandData = 0;
+  Status = MmCpuIo->Io.Read (
+                         MmCpuIo,
+                         MM_IO_UINT32,
+                         ICH9_CPU_HOTPLUG_BASE + QEMU_CPUHP_RW_CMD_DATA,
+                         1,
+                         &CommandData
+                         );
+  if (EFI_ERROR (Status)) {
+    DEBUG ((DEBUG_ERROR, "%a: %r\n", __FUNCTION__, Status));
+    ASSERT (FALSE);
+    CpuDeadLoop ();
+  }
+  return CommandData;
+}
+
+VOID
+QemuCpuhpWriteCpuSelector (
+  IN CONST EFI_MM_CPU_IO_PROTOCOL *MmCpuIo,
+  IN UINT32                       Selector
+  )
+{
+  EFI_STATUS Status;
+
+  Status = MmCpuIo->Io.Write (
+                         MmCpuIo,
+                         MM_IO_UINT32,
+                         ICH9_CPU_HOTPLUG_BASE + QEMU_CPUHP_W_CPU_SEL,
+                         1,
+                         &Selector
+                         );
+  if (EFI_ERROR (Status)) {
+    DEBUG ((DEBUG_ERROR, "%a: %r\n", __FUNCTION__, Status));
+    ASSERT (FALSE);
+    CpuDeadLoop ();
+  }
+}
+
+VOID
+QemuCpuhpWriteCommand (
+  IN CONST EFI_MM_CPU_IO_PROTOCOL *MmCpuIo,
+  IN UINT8                        Command
+  )
+{
+  EFI_STATUS Status;
+
+  Status = MmCpuIo->Io.Write (
+                         MmCpuIo,
+                         MM_IO_UINT8,
+                         ICH9_CPU_HOTPLUG_BASE + QEMU_CPUHP_W_CMD,
+                         1,
+                         &Command
+                         );
+  if (EFI_ERROR (Status)) {
+    DEBUG ((DEBUG_ERROR, "%a: %r\n", __FUNCTION__, Status));
+    ASSERT (FALSE);
+    CpuDeadLoop ();
+  }
+}
-- 
2.19.1.3.g30247aa5d201