ArmPkg/ArmSmcPsciResetSystemLib: implement fallback for warm reboot

Implement ResetSystemLib's EnterS3WithImmediateWake() routine using
a jump back to the PEI entry point with interrupts and MMU+caches
disabled. This is only possible at boot time, when we are sure that
the current CPU is the only one up and running. Also, it depends on
the platform whether the PEI code is preserved in memory (it may be
copied to DRAM rather than execute in place), so also add a feature
PCD to selectively enable this feature.

Contributed-under: TianoCore Contribution Agreement 1.1
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Reviewed-by: Leif Lindholm <leif.lindholm@linaro.org>

ArmPkg/ArmPkg.dec

@@ -85,6 +85,10 @@
   # Define if the GICv3 controller should use the GICv2 legacy
   gArmTokenSpaceGuid.PcdArmGicV3WithV2Legacy|FALSE|BOOLEAN|0x00000042
 
+  # Whether to implement warm reboot for capsule update using a jump back to the
+  # PEI entry point with caches and interrupts disabled.
+  gArmTokenSpaceGuid.PcdArmReenterPeiForCapsuleWarmReboot|FALSE|BOOLEAN|0x0000001F
+
 [PcdsFeatureFlag.ARM]
   # Whether to map normal memory as non-shareable. FALSE is the safe choice, but
   # TRUE may be appropriate to fix performance problems if you don't care about

ArmPkg/Library/ArmSmcPsciResetSystemLib/ArmSmcPsciResetSystemLib.c

@@ -15,10 +15,13 @@
 
 #include <PiDxe.h>
 
+#include <Library/ArmMmuLib.h>
+#include <Library/ArmSmcLib.h>
 #include <Library/BaseLib.h>
 #include <Library/DebugLib.h>
 #include <Library/ResetSystemLib.h>
-#include <Library/ArmSmcLib.h>
+#include <Library/UefiBootServicesTableLib.h>
+#include <Library/UefiRuntimeLib.h>
 
 #include <IndustryStandard/ArmStdSmc.h>
 
@@ -89,7 +92,21 @@ EnterS3WithImmediateWake (
   VOID
   )
 {
-  // Not implemented
+  VOID (*Reset)(VOID);
+
+  if (FeaturePcdGet (PcdArmReenterPeiForCapsuleWarmReboot) &&
+      !EfiAtRuntime ()) {
+    //
+    // At boot time, we are the only core running, so we can implement the
+    // immediate wake (which is used by capsule update) by disabling the MMU
+    // and interrupts, and jumping to the PEI entry point.
+    //
+    Reset = (VOID (*)(VOID))(UINTN)FixedPcdGet64 (PcdFvBaseAddress);
+
+    gBS->RaiseTPL (TPL_HIGH_LEVEL);
+    ArmDisableMmu ();
+    Reset ();
+  }
 }
 
 /**

ArmPkg/Library/ArmSmcPsciResetSystemLib/ArmSmcPsciResetSystemLib.inf

@@ -30,6 +30,15 @@
   MdePkg/MdePkg.dec
 
 [LibraryClasses]
+  ArmMmuLib
   ArmSmcLib
   BaseLib
   DebugLib
+  UefiBootServicesTableLib
+  UefiRuntimeLib
+
+[FeaturePcd]
+  gArmTokenSpaceGuid.PcdArmReenterPeiForCapsuleWarmReboot
+
+[FixedPcd]
+  gArmTokenSpaceGuid.PcdFvBaseAddress