From c98f7f75508912c086158892fc56b0c3b85abcf1 Mon Sep 17 00:00:00 2001
From: Ard Biesheuvel <ardb@kernel.org>
Date: Mon, 13 May 2024 18:43:11 +0200
Subject: ArmVirtPkg: Use dynamic PCD to set the SMCCC conduit

On ARM systems, whether SMC or HVC instructions need to be used to issue
monitor calls is typically dependent on the exception level, but there
are also cases where EL1 might use SMC instructions, so there is no hard
and fast rule.

For ArmVirtQemu, this does depend strictly on the exception level, so
set the default to HVC (for EL1 execution) and override it to SMC when
booted at EL2.

Cc: Ard Biesheuvel <ardb+tianocore@kernel.org>
Cc: Leif Lindholm <quic_llindhol@quicinc.com>
Cc: Sami Mujawar <sami.mujawar@arm.com>
Cc: Gerd Hoffmann <kraxel@redhat.com>

Committed-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Doug Flick [MSFT] <doug.edk2@gmail.com>
Reviewed-by: Ard Biesheuvel <ardb@kernel.org>
---
 ArmVirtPkg/ArmVirtCloudHv.dsc                        |  3 +++
 ArmVirtPkg/ArmVirtQemu.dsc                           |  4 ++++
 ArmVirtPkg/ArmVirtQemuKernel.dsc                     |  2 ++
 ArmVirtPkg/ArmVirtXen.dsc                            |  2 ++
 ArmVirtPkg/Library/PlatformPeiLib/PlatformPeiLib.c   | 14 ++++++++++++++
 ArmVirtPkg/Library/PlatformPeiLib/PlatformPeiLib.inf |  1 +
 6 files changed, 26 insertions(+)

diff --git a/ArmVirtPkg/ArmVirtCloudHv.dsc b/ArmVirtPkg/ArmVirtCloudHv.dsc
index 5cb2a60..d5055a0 100644
--- a/ArmVirtPkg/ArmVirtCloudHv.dsc
+++ b/ArmVirtPkg/ArmVirtCloudHv.dsc
@@ -201,6 +201,9 @@
 [PcdsDynamicHii]
   gUefiOvmfPkgTokenSpaceGuid.PcdForceNoAcpi|L"ForceNoAcpi"|gOvmfVariableGuid|0x0|FALSE|NV,BS
 
+[PcdsPatchableInModule.common]
+  gArmTokenSpaceGuid.PcdMonitorConduitHvc|TRUE
+
 ################################################################################
 #
 # Components Section - list of all EDK II Modules needed by this Platform
diff --git a/ArmVirtPkg/ArmVirtQemu.dsc b/ArmVirtPkg/ArmVirtQemu.dsc
index 4498ca5..80dd4fb 100644
--- a/ArmVirtPkg/ArmVirtQemu.dsc
+++ b/ArmVirtPkg/ArmVirtQemu.dsc
@@ -293,6 +293,10 @@
   gEfiNetworkPkgTokenSpaceGuid.PcdIPv4PXESupport|0x01
   gEfiNetworkPkgTokenSpaceGuid.PcdIPv6PXESupport|0x01
 
+  # whether to use HVC or SMC to issue monitor calls - this typically depends
+  # on the exception level at which the UEFI system firmware executes
+  gArmTokenSpaceGuid.PcdMonitorConduitHvc|TRUE
+
   #
   # TPM2 support
   #
diff --git a/ArmVirtPkg/ArmVirtQemuKernel.dsc b/ArmVirtPkg/ArmVirtQemuKernel.dsc
index 94f4859..2700b97 100644
--- a/ArmVirtPkg/ArmVirtQemuKernel.dsc
+++ b/ArmVirtPkg/ArmVirtQemuKernel.dsc
@@ -203,6 +203,8 @@
   gArmTokenSpaceGuid.PcdFdBaseAddress|0x0
   gArmTokenSpaceGuid.PcdFvBaseAddress|0x0
 
+  gArmTokenSpaceGuid.PcdMonitorConduitHvc|TRUE
+
 [PcdsDynamicDefault.common]
   gEfiMdePkgTokenSpaceGuid.PcdPlatformBootTimeOut|3
 
diff --git a/ArmVirtPkg/ArmVirtXen.dsc b/ArmVirtPkg/ArmVirtXen.dsc
index 5809832..ceb37f8 100644
--- a/ArmVirtPkg/ArmVirtXen.dsc
+++ b/ArmVirtPkg/ArmVirtXen.dsc
@@ -120,6 +120,8 @@
   gArmTokenSpaceGuid.PcdFdBaseAddress|0x0
   gArmTokenSpaceGuid.PcdFvBaseAddress|0x0
 
+  gArmTokenSpaceGuid.PcdMonitorConduitHvc|TRUE
+
 [PcdsDynamicDefault.common]
 
   gArmTokenSpaceGuid.PcdArmArchTimerSecIntrNum|0x0
diff --git a/ArmVirtPkg/Library/PlatformPeiLib/PlatformPeiLib.c b/ArmVirtPkg/Library/PlatformPeiLib/PlatformPeiLib.c
index 7ab4aa2..b8e9208 100644
--- a/ArmVirtPkg/Library/PlatformPeiLib/PlatformPeiLib.c
+++ b/ArmVirtPkg/Library/PlatformPeiLib/PlatformPeiLib.c
@@ -18,6 +18,8 @@
 #include <Library/FdtSerialPortAddressLib.h>
 #include <libfdt.h>
 
+#include <Chipset/AArch64.h>
+
 #include <Guid/EarlyPL011BaseAddress.h>
 #include <Guid/FdtHob.h>
 
@@ -224,5 +226,17 @@ PlatformPeim (
 
   BuildFvHob (PcdGet64 (PcdFvBaseAddress), PcdGet32 (PcdFvSize));
 
+ #ifdef MDE_CPU_AARCH64
+  //
+  // Set the SMCCC conduit to SMC if executing at EL2, which is typically the
+  // exception level that services HVCs rather than the one that invokes them.
+  //
+  if (ArmReadCurrentEL () == AARCH64_EL2) {
+    Status = PcdSetBoolS (PcdMonitorConduitHvc, FALSE);
+    ASSERT_EFI_ERROR (Status);
+  }
+
+ #endif
+
   return EFI_SUCCESS;
 }
diff --git a/ArmVirtPkg/Library/PlatformPeiLib/PlatformPeiLib.inf b/ArmVirtPkg/Library/PlatformPeiLib/PlatformPeiLib.inf
index e9a34b6..a38b89c1 100644
--- a/ArmVirtPkg/Library/PlatformPeiLib/PlatformPeiLib.inf
+++ b/ArmVirtPkg/Library/PlatformPeiLib/PlatformPeiLib.inf
@@ -45,6 +45,7 @@
 
 [Pcd]
   gArmTokenSpaceGuid.PcdFvBaseAddress
+  gArmTokenSpaceGuid.PcdMonitorConduitHvc
   gEfiSecurityPkgTokenSpaceGuid.PcdTpmBaseAddress             ## SOMETIMES_PRODUCES
   gUefiOvmfPkgTokenSpaceGuid.PcdDeviceTreeInitialBaseAddress
 
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