From f668e78871659f438ed4548650ffd07c31a429b5 Mon Sep 17 00:00:00 2001
From: Laszlo Ersek <lersek@redhat.com>
Date: Wed, 26 Feb 2020 23:11:48 +0100
Subject: [PATCH] OvmfPkg/CpuHotplugSmm: define the QEMU_CPUHP_CMD_GET_ARCH_ID
 macro
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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>
Message-Id: <20200226221156.29589-9-lersek@redhat.com>
Reviewed-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Reviewed-by: Philippe Mathieu-Daude <philmd@redhat.com>
Tested-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
---
 OvmfPkg/CpuHotplugSmm/CpuHotplug.c            | 35 +++++++++++++++++++
 .../Include/IndustryStandard/QemuCpuHotplug.h |  1 +
 2 files changed, 36 insertions(+)

diff --git a/OvmfPkg/CpuHotplugSmm/CpuHotplug.c b/OvmfPkg/CpuHotplugSmm/CpuHotplug.c
index fd09403eab..5df8c689c6 100644
--- a/OvmfPkg/CpuHotplugSmm/CpuHotplug.c
+++ b/OvmfPkg/CpuHotplugSmm/CpuHotplug.c
@@ -7,6 +7,7 @@
 **/
 
 #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
@@ -14,6 +15,8 @@
 #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.
 //
@@ -168,6 +171,38 @@ CpuHotplugEntry (
     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.
   //
diff --git a/OvmfPkg/Include/IndustryStandard/QemuCpuHotplug.h b/OvmfPkg/Include/IndustryStandard/QemuCpuHotplug.h
index cf0745610f..3d01363350 100644
--- a/OvmfPkg/Include/IndustryStandard/QemuCpuHotplug.h
+++ b/OvmfPkg/Include/IndustryStandard/QemuCpuHotplug.h
@@ -39,5 +39,6 @@
 
 #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_