ArmVirtPkg: Implement DT-based ArmMonitorLib for the PEI phase

The TPM2 related PEIMs depend on ResetSystemLib too, and so in order to
be able to switch to the generic ArmPkg implementation which relies on
ArmMonitorLib, the latter library class requires a PEIM-compatible
implementation too.

Signed-off-by: Ard Biesheuvel <ardb@kernel.org>

ArmVirtPkg/Library/ArmVirtQemuMonitorPeiLib/ArmVirtQemuMonitorPeiLib.c

@@ -0,0 +1,128 @@
+/** @file
+  Arm Monitor Library that chooses the conduit based on the PSCI node in the
+  device tree provided by QEMU.
+
+  Copyright (c) 2022, Arm Limited. All rights reserved.<BR>
+  Copyright (c) 2024, Google LLC. All rights reserved.<BR>
+
+  SPDX-License-Identifier: BSD-2-Clause-Patent
+
+**/
+
+#include <Base.h>
+
+#include <Library/ArmHvcLib.h>
+#include <Library/ArmMonitorLib.h>
+#include <Library/ArmSmcLib.h>
+#include <Library/BaseLib.h>
+#include <Library/DebugLib.h>
+#include <Library/FdtLib.h>
+
+typedef enum {
+  SmcccConduitUnknown,
+  SmcccConduitSmc,
+  SmcccConduitHvc,
+} SMCCC_CONDUIT;
+
+/**
+  Discover the SMCCC conduit by parsing the PSCI device tree node.
+
+  @return the discovered SMCCC conduit
+**/
+STATIC
+SMCCC_CONDUIT
+DiscoverSmcccConduit (
+  VOID
+  )
+{
+  VOID                *DeviceTreeBase;
+  INT32               Node, Prev;
+  INT32               Len;
+  CONST FDT_PROPERTY  *Compatible;
+  CONST CHAR8         *CompatibleItem;
+  CONST FDT_PROPERTY  *Prop;
+
+  DeviceTreeBase = (VOID *)(UINTN)PcdGet64 (PcdDeviceTreeInitialBaseAddress);
+  ASSERT (FdtCheckHeader (DeviceTreeBase) == 0);
+
+  //
+  // Enumerate all FDT nodes looking for the PSCI node and capture the conduit
+  //
+  for (Prev = 0; ; Prev = Node) {
+    Node = FdtNextNode (DeviceTreeBase, Prev, NULL);
+    if (Node < 0) {
+      break;
+    }
+
+    Compatible = FdtGetProperty (DeviceTreeBase, Node, "compatible", &Len);
+    if (Compatible == NULL) {
+      continue;
+    }
+
+    //
+    // Iterate over the NULL-separated items in the compatible string
+    //
+    for (CompatibleItem = Compatible->Data; CompatibleItem < Compatible->Data + Len;
+         CompatibleItem += 1 + AsciiStrLen (CompatibleItem))
+    {
+      if (AsciiStrCmp (CompatibleItem, "arm,psci-0.2") != 0) {
+        continue;
+      }
+
+      Prop = FdtGetProperty (DeviceTreeBase, Node, "method", NULL);
+      if (Prop == NULL) {
+        DEBUG ((
+          DEBUG_ERROR,
+          "%a: Missing PSCI method property\n",
+          __func__
+          ));
+
+        return SmcccConduitUnknown;
+      }
+
+      if (AsciiStrnCmp (Prop->Data, "hvc", 3) == 0) {
+        return SmcccConduitHvc;
+      } else if (AsciiStrnCmp (Prop->Data, "smc", 3) == 0) {
+        return SmcccConduitSmc;
+      } else {
+        DEBUG ((
+          DEBUG_ERROR,
+          "%a: Unknown PSCI method \"%a\"\n",
+          __func__,
+          Prop
+          ));
+
+        return SmcccConduitUnknown;
+      }
+    }
+  }
+
+  return SmcccConduitUnknown;
+}
+
+/** Monitor call.
+
+  An HyperVisor Call (HVC) or System Monitor Call (SMC) will be issued
+  depending on the default conduit.
+
+  @param [in,out]  Args    Arguments for the HVC/SMC.
+**/
+VOID
+EFIAPI
+ArmMonitorCall (
+  IN OUT ARM_MONITOR_ARGS  *Args
+  )
+{
+  switch (DiscoverSmcccConduit ()) {
+    case SmcccConduitHvc:
+      ArmCallHvc ((ARM_HVC_ARGS *)Args);
+      break;
+
+    case SmcccConduitSmc:
+      ArmCallSmc ((ARM_SMC_ARGS *)Args);
+      break;
+
+    default:
+      ASSERT (FALSE);
+  }
+}

ArmVirtPkg/Library/ArmVirtQemuMonitorPeiLib/ArmVirtQemuMonitorPeiLib.inf

@@ -0,0 +1,35 @@
+## @file
+#  Arm Monitor Library that chooses the conduit based on the PSCI node in the
+#  device tree provided by QEMU.
+#
+#  Copyright (c) 2022, Arm Limited. All rights reserved.<BR>
+#  Copyright (c) 2024, Google LLC. All rights reserved.<BR>
+#
+#  SPDX-License-Identifier: BSD-2-Clause-Patent
+##
+
+[Defines]
+  INF_VERSION                    = 1.29
+  BASE_NAME                      = ArmVirtQemuMonitorPeiLib
+  FILE_GUID                      = c610e0dc-dd7a-47c8-8fea-26c4710709ff
+  MODULE_TYPE                    = BASE
+  VERSION_STRING                 = 1.0
+  LIBRARY_CLASS                  = ArmMonitorLib|PEIM
+
+[Sources]
+  ArmVirtQemuMonitorPeiLib.c
+
+[Packages]
+  ArmPkg/ArmPkg.dec
+  MdePkg/MdePkg.dec
+  OvmfPkg/OvmfPkg.dec
+
+[LibraryClasses]
+  ArmHvcLib
+  ArmSmcLib
+  BaseLib
+  DebugLib
+  FdtLib
+
+[Pcd]
+  gUefiOvmfPkgTokenSpaceGuid.PcdDeviceTreeInitialBaseAddress