[PATCH 1/5] MdeModulePkg/CapsulePei: clean Dcache before consuming capsule data

[Ard Biesheuvel <ard.biesheuvel@linaro.org>]

When capsule updates are staged for processing after a warm reboot,
they are copied into memory with the MMU and caches enabled. When
the capsule PEI gets around to coalescing the capsule, the MMU and
caches may still be disabled, and so on architectures where uncached
accesses are incoherent with the caches (such as ARM and AARCH64),
we may read stale data if we don't clean the caches to memory first.

Note that this cache maintenance cannot be done during the invocation
of UpdateCapsule(), since the ScatterGatherList structures are only
identified by physical address, and at runtime, the firmware doesn't
know whether and where this memory is mapped, and cache maintenance
requires a virtual address.

Reviewed-by: Jiewen Yao <jiewen.yao@intel.com>
Contributed-under: TianoCore Contribution Agreement 1.1
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
---
 MdeModulePkg/Universal/CapsulePei/CapsulePei.inf           |  1 +
 MdeModulePkg/Universal/CapsulePei/Common/CapsuleCoalesce.c | 10 ++++++++++
 2 files changed, 11 insertions(+)

diff --git a/MdeModulePkg/Universal/CapsulePei/CapsulePei.inf b/MdeModulePkg/Universal/CapsulePei/CapsulePei.inf
index c54bc21a95a8..594e110d1f8a 100644
--- a/MdeModulePkg/Universal/CapsulePei/CapsulePei.inf
+++ b/MdeModulePkg/Universal/CapsulePei/CapsulePei.inf
@@ -48,6 +48,7 @@ [Packages]
 
 [LibraryClasses]
   BaseLib
+  CacheMaintenanceLib
   HobLib
   BaseMemoryLib
   PeiServicesLib
diff --git a/MdeModulePkg/Universal/CapsulePei/Common/CapsuleCoalesce.c b/MdeModulePkg/Universal/CapsulePei/Common/CapsuleCoalesce.c
index 3e7054cd38a9..fb59f338f100 100644
--- a/MdeModulePkg/Universal/CapsulePei/Common/CapsuleCoalesce.c
+++ b/MdeModulePkg/Universal/CapsulePei/Common/CapsuleCoalesce.c
@@ -27,6 +27,7 @@ WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.
 #include <Guid/CapsuleVendor.h>
 
 #include <Library/BaseMemoryLib.h>
+#include <Library/CacheMaintenanceLib.h>
 #include <Library/DebugLib.h>
 #include <Library/PrintLib.h>
 #include <Library/BaseLib.h>
@@ -274,6 +275,7 @@ ValidateCapsuleByMemoryResource (
     //
     // No memory resource descriptor reported in HOB list before capsule Coalesce.
     //
+    WriteBackDataCacheRange ((VOID *)(UINTN)Address, (UINTN)Size);
     return TRUE;
   }
 
@@ -283,6 +285,14 @@ ValidateCapsuleByMemoryResource (
       DEBUG ((EFI_D_INFO, "Address(0x%lx) Size(0x%lx) in MemoryResource[0x%x] - Start(0x%lx) Length(0x%lx)\n",
                           Address, Size,
                           Index, MemoryResource[Index].PhysicalStart, MemoryResource[Index].ResourceLength));
+
+      //
+      // At this point, we may still be running with the MMU and caches disabled,
+      // and on architectures such as ARM or AARCH64, capsule [meta]data loaded
+      // into memory with the caches on is only guaranteed to be visible to the
+      // CPU running with the caches off after performing an explicit writeback.
+      //
+      WriteBackDataCacheRange ((VOID *)(UINTN)Address, (UINTN)Size);
       return TRUE;
     }
   }
-- 
2.17.0