[Xen-devel] [PATCH v2 08/29] ArmVirtualizationPkg: add padding to FDT allocation

[Ard Biesheuvel <ard.biesheuvel@xxxxxxxxxx>]

Our primary user QEMU/mach-virt presents us with a FDT blob padded
to 64 KB with plenty of room to set additional properties. However,
in the general case, we should only add properties after making sure
there is enough room available.

Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@xxxxxxxxxx>
---
 ArmPlatformPkg/ArmVirtualizationPkg/Library/PlatformPeiLib/PlatformPeiLib.c | 
17 ++++++++++++++---
 1 file changed, 14 insertions(+), 3 deletions(-)

diff --git 
a/ArmPlatformPkg/ArmVirtualizationPkg/Library/PlatformPeiLib/PlatformPeiLib.c 
b/ArmPlatformPkg/ArmVirtualizationPkg/Library/PlatformPeiLib/PlatformPeiLib.c
index c500d5964b25..42a87309aebe 100644
--- 
a/ArmPlatformPkg/ArmVirtualizationPkg/Library/PlatformPeiLib/PlatformPeiLib.c
+++ 
b/ArmPlatformPkg/ArmVirtualizationPkg/Library/PlatformPeiLib/PlatformPeiLib.c
@@ -24,6 +24,15 @@
 #include <Guid/EarlyPL011BaseAddress.h>
 #include <Guid/FdtHob.h>
 
+//
+// We may want to apply some changes to the device tree before passing it
+// to the OS: for instance, if we find a PL031 RTC node and attach our
+// runtime driver to it, we should disable it in the device tree by setting
+// its status property to "disabled". Add some padding to make sure this is
+// possible.
+//
+#define FDT_PADDING   256
+
 EFI_STATUS
 EFIAPI
 PlatformPeim (
@@ -33,6 +42,7 @@ PlatformPeim (
   VOID               *Base;
   VOID               *NewBase;
   UINTN              FdtSize;
+  UINTN              FdtPages;
   UINT64             *FdtHobData;
   UINT64             *UartHobData;
   INT32              Node, Prev;
@@ -47,10 +57,11 @@ PlatformPeim (
   ASSERT (Base != NULL);
   ASSERT (fdt_check_header (Base) == 0);
 
-  FdtSize = fdt_totalsize (Base);
-  NewBase = AllocatePages (EFI_SIZE_TO_PAGES (FdtSize));
+  FdtSize = fdt_totalsize (Base) + FDT_PADDING;
+  FdtPages = EFI_SIZE_TO_PAGES (FdtSize);
+  NewBase = AllocatePages (FdtPages);
   ASSERT (NewBase != NULL);
-  CopyMem (NewBase, Base, FdtSize);
+  fdt_open_into (Base, NewBase, EFI_PAGES_TO_SIZE (FdtPages));
 
   FdtHobData = BuildGuidHob (&gFdtHobGuid, sizeof *FdtHobData);
   ASSERT (FdtHobData != NULL);
-- 
1.8.3.2


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