[PATCH v2 08/16] OvmfPkg/CpuHotplugSmm: define the QEMU_CPUHP_CMD_GET_ARCH_ID macro

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

QEMU commit 3a61c8db9d25 ("acpi: cpuhp: add CPHP_GET_CPU_ID_CMD command",
2020-01-22) introduced a new command in the modern CPU hotplug register
block that lets the firmware query the arch-specific IDs (on IA32/X64: the
APIC IDs) of CPUs. Add a macro for this command value, because we'll need
it later.

At the same time, add a sanity check for the modern hotplug interface to
CpuHotplugSmm.

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/Include/IndustryStandard/QemuCpuHotplug.h |  1 +
 OvmfPkg/CpuHotplugSmm/CpuHotplug.c                | 35 ++++++++++++++++++++
 2 files changed, 36 insertions(+)

diff --git a/OvmfPkg/Include/IndustryStandard/QemuCpuHotplug.h b/OvmfPkg/Include/IndustryStandard/QemuCpuHotplug.h
index cf0745610f2c..3d013633501b 100644
--- a/OvmfPkg/Include/IndustryStandard/QemuCpuHotplug.h
+++ b/OvmfPkg/Include/IndustryStandard/QemuCpuHotplug.h
@@ -20,24 +20,25 @@
 #define QEMU_CPU_HOTPLUG_H_
 
 #include <Base.h>
 
 //
 // Each register offset is:
 // - relative to the board-dependent IO base address of the register block,
 // - named QEMU_CPUHP_(R|W|RW)_*, according to the possible access modes of the
 //   register,
 // - followed by distinguished bitmasks or values in the register.
 //
 #define QEMU_CPUHP_R_CMD_DATA2               0x0
 
 #define QEMU_CPUHP_R_CPU_STAT                0x4
 #define QEMU_CPUHP_STAT_ENABLED                BIT0
 
 #define QEMU_CPUHP_RW_CMD_DATA               0x8
 
 #define QEMU_CPUHP_W_CPU_SEL                 0x0
 
 #define QEMU_CPUHP_W_CMD                     0x5
 #define QEMU_CPUHP_CMD_GET_PENDING             0x0
+#define QEMU_CPUHP_CMD_GET_ARCH_ID             0x3
 
 #endif // QEMU_CPU_HOTPLUG_H_
diff --git a/OvmfPkg/CpuHotplugSmm/CpuHotplug.c b/OvmfPkg/CpuHotplugSmm/CpuHotplug.c
index fd09403eabf3..5df8c689c63a 100644
--- a/OvmfPkg/CpuHotplugSmm/CpuHotplug.c
+++ b/OvmfPkg/CpuHotplugSmm/CpuHotplug.c
@@ -1,38 +1,41 @@
 /** @file
   Root SMI handler for VCPU hotplug SMIs.
 
   Copyright (c) 2020, Red Hat, Inc.
 
   SPDX-License-Identifier: BSD-2-Clause-Patent
 **/
 
 #include <IndustryStandard/Q35MchIch9.h>     // ICH9_APM_CNT
+#include <IndustryStandard/QemuCpuHotplug.h> // QEMU_CPUHP_CMD_GET_PENDING
 #include <Library/BaseLib.h>                 // CpuDeadLoop()
 #include <Library/DebugLib.h>                // ASSERT()
 #include <Library/MmServicesTableLib.h>      // gMmst
 #include <Library/PcdLib.h>                  // PcdGetBool()
 #include <Protocol/MmCpuIo.h>                // EFI_MM_CPU_IO_PROTOCOL
 #include <Uefi/UefiBaseType.h>               // EFI_STATUS
 
+#include "QemuCpuhp.h"                       // QemuCpuhpWriteCpuSelector()
+
 //
 // We use this protocol for accessing IO Ports.
 //
 STATIC EFI_MM_CPU_IO_PROTOCOL *mMmCpuIo;
 //
 // Represents the registration of the CPU Hotplug MMI handler.
 //
 STATIC EFI_HANDLE mDispatchHandle;
 
 
 /**
   CPU Hotplug MMI handler function.
 
   This is a root MMI handler.
 
   @param[in] DispatchHandle      The unique handle assigned to this handler by
                                  EFI_MM_SYSTEM_TABLE.MmiHandlerRegister().
 
   @param[in] Context             Context passed in by
                                  EFI_MM_SYSTEM_TABLE.MmiManage(). Due to
                                  CpuHotplugMmi() being a root MMI handler,
                                  Context is ASSERT()ed to be NULL.
@@ -149,43 +152,75 @@ CpuHotplugEntry (
   //
   // This driver depends on the dynamically detected "SMRAM at default SMBASE"
   // feature.
   //
   if (!PcdGetBool (PcdQ35SmramAtDefaultSmbase)) {
     return EFI_UNSUPPORTED;
   }
 
   //
   // Errors from here on are fatal; we cannot allow the boot to proceed if we
   // can't set up this driver to handle CPU hotplug.
   //
   // First, collect the protocols needed later. All of these protocols are
   // listed in our module DEPEX.
   //
   Status = gMmst->MmLocateProtocol (&gEfiMmCpuIoProtocolGuid,
                     NULL /* Registration */, (VOID **)&mMmCpuIo);
   if (EFI_ERROR (Status)) {
     DEBUG ((DEBUG_ERROR, "%a: locate MmCpuIo: %r\n", __FUNCTION__, Status));
     goto Fatal;
   }
 
+  //
+  // Sanity-check the CPU hotplug interface.
+  //
+  // Both of the following features are part of QEMU 5.0, introduced primarily
+  // in commit range 3e08b2b9cb64..3a61c8db9d25:
+  //
+  // (a) the QEMU_CPUHP_CMD_GET_ARCH_ID command of the modern CPU hotplug
+  //     interface,
+  //
+  // (b) the "SMRAM at default SMBASE" feature.
+  //
+  // From these, (b) is restricted to 5.0+ machine type versions, while (a)
+  // does not depend on machine type version. Because we ensured the stricter
+  // condition (b) through PcdQ35SmramAtDefaultSmbase above, the (a)
+  // QEMU_CPUHP_CMD_GET_ARCH_ID command must now be available too. While we
+  // can't verify the presence of precisely that command, we can still verify
+  // (sanity-check) that the modern interface is active, at least.
+  //
+  // Consult the "Typical usecases | Detecting and enabling modern CPU hotplug
+  // interface" section in QEMU's "docs/specs/acpi_cpu_hotplug.txt", on the
+  // following.
+  //
+  QemuCpuhpWriteCpuSelector (mMmCpuIo, 0);
+  QemuCpuhpWriteCpuSelector (mMmCpuIo, 0);
+  QemuCpuhpWriteCommand (mMmCpuIo, QEMU_CPUHP_CMD_GET_PENDING);
+  if (QemuCpuhpReadCommandData2 (mMmCpuIo) != 0) {
+    Status = EFI_NOT_FOUND;
+    DEBUG ((DEBUG_ERROR, "%a: modern CPU hotplug interface: %r\n",
+      __FUNCTION__, Status));
+    goto Fatal;
+  }
+
   //
   // Register the handler for the CPU Hotplug MMI.
   //
   Status = gMmst->MmiHandlerRegister (
                     CpuHotplugMmi,
                     NULL,            // HandlerType: root MMI handler
                     &mDispatchHandle
                     );
   if (EFI_ERROR (Status)) {
     DEBUG ((DEBUG_ERROR, "%a: MmiHandlerRegister(): %r\n", __FUNCTION__,
       Status));
     goto Fatal;
   }
 
   return EFI_SUCCESS;
 
 Fatal:
   ASSERT (FALSE);
   CpuDeadLoop ();
   return Status;
 }
-- 
2.19.1.3.g30247aa5d201