Re: [PATCH v1 06/12] StandaloneMmPkg: Add option to use FF-A calls for getting SPM version

["Sami Mujawar" <sami.mujawar@arm.com>]

Hi Sughosh,

Please find my response inline marked [SAMI].

Regards,

Sami Mujawar

-----Original Message-----
From: Sughosh Ganu <sughosh.ganu@linaro.org> 
Sent: 21 October 2020 12:32 PM
To: devel@edk2.groups.io
Cc: Ard Biesheuvel <Ard.Biesheuvel@arm.com>; Sami Mujawar <Sami.Mujawar@arm.com>; Jiewen Yao <jiewen.yao@intel.com>; Achin Gupta <Achin.Gupta@arm.com>
Subject: [PATCH v1 06/12] StandaloneMmPkg: Add option to use FF-A calls for getting SPM version

From: Achin Gupta <achin.gupta@arm.com>

With the introduction of Firmware Framework(FF-A), a Secure Partition
can get the SPM version either using FF-A calls or through the
existing svc calls. Use a runtime check to use either of the two
methods based on the Pcd feature flag value.

Signed-off-by: Achin Gupta <achin.gupta@arm.com>
Co-developed-by: Sughosh Ganu <sughosh.ganu@linaro.org>
---
 StandaloneMmPkg/Library/StandaloneMmCoreEntryPoint/StandaloneMmCoreEntryPoint.inf       |  3 ++
 StandaloneMmPkg/Library/StandaloneMmCoreEntryPoint/AArch64/StandaloneMmCoreEntryPoint.c | 31 ++++++++++++++------
 2 files changed, 25 insertions(+), 9 deletions(-)

diff --git a/StandaloneMmPkg/Library/StandaloneMmCoreEntryPoint/StandaloneMmCoreEntryPoint.inf b/StandaloneMmPkg/Library/StandaloneMmCoreEntryPoint/StandaloneMmCoreEntryPoint.inf
index 7d6ee4e08e..f8184f501b 100644
--- a/StandaloneMmPkg/Library/StandaloneMmCoreEntryPoint/StandaloneMmCoreEntryPoint.inf
+++ b/StandaloneMmPkg/Library/StandaloneMmCoreEntryPoint/StandaloneMmCoreEntryPoint.inf
@@ -49,5 +49,8 @@
   gEfiStandaloneMmNonSecureBufferGuid
   gEfiArmTfCpuDriverEpDescriptorGuid
 
+[Pcd]
+  gArmTokenSpaceGuid.PcdFfaEnable
+
 [BuildOptions]
   GCC:*_*_*_CC_FLAGS = -fpie
diff --git a/StandaloneMmPkg/Library/StandaloneMmCoreEntryPoint/AArch64/StandaloneMmCoreEntryPoint.c b/StandaloneMmPkg/Library/StandaloneMmCoreEntryPoint/AArch64/StandaloneMmCoreEntryPoint.c
index 33f0db654f..7d1e3c4d7c 100644
--- a/StandaloneMmPkg/Library/StandaloneMmCoreEntryPoint/AArch64/StandaloneMmCoreEntryPoint.c
+++ b/StandaloneMmPkg/Library/StandaloneMmCoreEntryPoint/AArch64/StandaloneMmCoreEntryPoint.c
@@ -23,6 +23,7 @@ SPDX-License-Identifier: BSD-2-Clause-Patent
 #include <Library/BaseLib.h>
 #include <Library/BaseMemoryLib.h>
 #include <Library/SerialPortLib.h>
+#include <Library/PcdLib.h>
 
 #include <IndustryStandard/ArmStdSmc.h>
 #include <IndustryStandard/ArmMmSvc.h>
@@ -165,19 +166,31 @@ EFI_STATUS
 GetSpmVersion (VOID)
 {
   EFI_STATUS   Status;
-  UINT16       SpmMajorVersion;
-  UINT16       SpmMinorVersion;
+  UINT16       CurSpmMajorVer;
+  UINT16       SpmMajorVer;

[SAMI] I think a 'Caller & Callee' prefix would add clarity. See FFA Spec, Section 8.1.1 [/SAMI]

+  UINT16       CurSpmMinorVer;
+  UINT16       SpmMinorVer;
   UINT32       SpmVersion;
   ARM_SVC_ARGS SpmVersionArgs;
 
-  SpmVersionArgs.Arg0 = ARM_SVC_ID_SPM_VERSION_AARCH32;
+  if (FeaturePcdGet (PcdFfaEnable)) {
+    SpmVersionArgs.Arg0 = ARM_SVC_ID_FFA_VERSION_AARCH32;
+    SpmVersionArgs.Arg1 = SPM_MAJOR_VER << SPM_MAJOR_VER_SHIFT;
+    SpmVersionArgs.Arg1 |= SPM_MINOR_VER;
+    SpmMajorVer = SPM_MAJOR_VER_FFA;
+    SpmMinorVer = SPM_MINOR_VER_FFA;
+  } else {
+    SpmVersionArgs.Arg0 = ARM_SVC_ID_SPM_VERSION_AARCH32;
+    SpmMajorVer = SPM_MAJOR_VER;
+    SpmMinorVer = SPM_MINOR_VER;
+  }
 
   ArmCallSvc (&SpmVersionArgs);
 
   SpmVersion = SpmVersionArgs.Arg0;

 [SAMI] The Version FID for FFA and for SPM based on the MM interface both return NOT_SUPPORTED as an error code. 
Can we check the error code for failure, please?
[/SAMI]

-  SpmMajorVersion = ((SpmVersion & SPM_MAJOR_VER_MASK) >> SPM_MAJOR_VER_SHIFT);
-  SpmMinorVersion = ((SpmVersion & SPM_MINOR_VER_MASK) >> 0);
+  CurSpmMajorVer = ((SpmVersion & SPM_MAJOR_VER_MASK) >> SPM_MAJOR_VER_SHIFT);
+  CurSpmMinorVer = ((SpmVersion & SPM_MINOR_VER_MASK) >> 0);
 
   // Different major revision values indicate possibly incompatible functions.
   // For two revisions, A and B, for which the major revision values are
@@ -186,17 +199,17 @@ GetSpmVersion (VOID)
   // revision A must work in a compatible way with revision B.
   // However, it is possible for revision B to have a higher
   // function count than revision A.
-  if ((SpmMajorVersion == SPM_MAJOR_VER) &&
-      (SpmMinorVersion >= SPM_MINOR_VER))
+  if ((CurSpmMajorVer == SpmMajorVer) &&
+      (CurSpmMinorVer >= SpmMinorVer))
   {
     DEBUG ((DEBUG_INFO, "SPM Version: Major=0x%x, Minor=0x%x\n",
-           SpmMajorVersion, SpmMinorVersion));
+           CurSpmMajorVer, CurSpmMinorVer));
     Status = EFI_SUCCESS;
   }
   else
   {
     DEBUG ((DEBUG_INFO, "Incompatible SPM Versions.\n Current Version: Major=0x%x, Minor=0x%x.\n Expected: Major=0x%x, Minor>=0x%x.\n",
-            SpmMajorVersion, SpmMinorVersion, SPM_MAJOR_VER, SPM_MINOR_VER));
+            CurSpmMajorVer, CurSpmMinorVer, SpmMajorVer, SpmMinorVer));
     Status = EFI_UNSUPPORTED;
   }
 
-- 
2.17.1