OvmfPkg/VirtNorFlashDxe: use EFI_MEMORY_WC and drop AlignedCopyMem()

NOR flash emulation under KVM involves switching between two modes,
where array mode is backed by a read-only memslot, and programming mode
is fully emulated, i.e., the memory region is not backed by anything,
and the faulting accesses are forwarded to the VMM by the hypervisor,
which translates them into NOR flash programming commands.

Normally, we are limited to the use of device attributes when mapping
such regions, given that the programming mode has MMIO semantics.
However, when running under KVM, the chosen memory attributes only take
effect when in array mode, since no memory mapping exists otherwise.

This means we can tune the memory mapping so it behaves a bit more like
a ROM, by switching to EFI_MEMORY_WC attributes. This means we no longer
need a special CopyMem() implementation that avoids unaligned accesses
at all cost.

Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Reviewed-by: Sunil V L <sunilvl@ventanamicro.com>

2 files changed, 4 insertions, 65 deletions

diff --git a/OvmfPkg/VirtNorFlashDxe/VirtNorFlash.c b/OvmfPkg/VirtNorFlashDxe/VirtNorFlash.c
index 0343131a54..1afd60ce66 100644
--- a/OvmfPkg/VirtNorFlashDxe/VirtNorFlash.c
+++ b/OvmfPkg/VirtNorFlashDxe/VirtNorFlash.c
@@ -401,67 +401,6 @@ NorFlashWriteBlocks (
   return Status;

 }

 

-#define BOTH_ALIGNED(a, b, align)  ((((UINTN)(a) | (UINTN)(b)) & ((align) - 1)) == 0)

-

-/**

-  Copy Length bytes from Source to Destination, using aligned accesses only.

-  Note that this implementation uses memcpy() semantics rather then memmove()

-  semantics, i.e., SourceBuffer and DestinationBuffer should not overlap.

-

-  @param  DestinationBuffer The target of the copy request.

-  @param  SourceBuffer      The place to copy from.

-  @param  Length            The number of bytes to copy.

-

-  @return Destination

-

-**/

-STATIC

-VOID *

-AlignedCopyMem (

-  OUT     VOID        *DestinationBuffer,

-  IN      CONST VOID  *SourceBuffer,

-  IN      UINTN       Length

-  )

-{

-  UINT8         *Destination8;

-  CONST UINT8   *Source8;

-  UINT32        *Destination32;

-  CONST UINT32  *Source32;

-  UINT64        *Destination64;

-  CONST UINT64  *Source64;

-

-  if (BOTH_ALIGNED (DestinationBuffer, SourceBuffer, 8) && (Length >= 8)) {

-    Destination64 = DestinationBuffer;

-    Source64      = SourceBuffer;

-    while (Length >= 8) {

-      *Destination64++ = *Source64++;

-      Length          -= 8;

-    }

-

-    Destination8 = (UINT8 *)Destination64;

-    Source8      = (CONST UINT8 *)Source64;

-  } else if (BOTH_ALIGNED (DestinationBuffer, SourceBuffer, 4) && (Length >= 4)) {

-    Destination32 = DestinationBuffer;

-    Source32      = SourceBuffer;

-    while (Length >= 4) {

-      *Destination32++ = *Source32++;

-      Length          -= 4;

-    }

-

-    Destination8 = (UINT8 *)Destination32;

-    Source8      = (CONST UINT8 *)Source32;

-  } else {

-    Destination8 = DestinationBuffer;

-    Source8      = SourceBuffer;

-  }

-

-  while (Length-- != 0) {

-    *Destination8++ = *Source8++;

-  }

-

-  return DestinationBuffer;

-}

-

 EFI_STATUS

 NorFlashReadBlocks (

   IN NOR_FLASH_INSTANCE  *Instance,

@@ -516,7 +455,7 @@ NorFlashReadBlocks (
   SEND_NOR_COMMAND (Instance->DeviceBaseAddress, 0, P30_CMD_READ_ARRAY);

 

   // Readout the data

-  AlignedCopyMem (Buffer, (VOID *)StartAddress, BufferSizeInBytes);

+  CopyMem (Buffer, (VOID *)StartAddress, BufferSizeInBytes);

 

   return EFI_SUCCESS;

 }

@@ -558,7 +497,7 @@ NorFlashRead (
   SEND_NOR_COMMAND (Instance->DeviceBaseAddress, 0, P30_CMD_READ_ARRAY);

 

   // Readout the data

-  AlignedCopyMem (Buffer, (VOID *)(StartAddress + Offset), BufferSizeInBytes);

+  CopyMem (Buffer, (VOID *)(StartAddress + Offset), BufferSizeInBytes);

 

   return EFI_SUCCESS;

 }

diff --git a/OvmfPkg/VirtNorFlashDxe/VirtNorFlashDxe.c b/OvmfPkg/VirtNorFlashDxe/VirtNorFlashDxe.c
index f9a41f6aab..ff3121af2a 100644
--- a/OvmfPkg/VirtNorFlashDxe/VirtNorFlashDxe.c
+++ b/OvmfPkg/VirtNorFlashDxe/VirtNorFlashDxe.c
@@ -394,14 +394,14 @@ NorFlashFvbInitialize (
                   EfiGcdMemoryTypeMemoryMappedIo,

                   Instance->DeviceBaseAddress,

                   RuntimeMmioRegionSize,

-                  EFI_MEMORY_UC | EFI_MEMORY_RUNTIME

+                  EFI_MEMORY_WC | EFI_MEMORY_RUNTIME

                   );

   ASSERT_EFI_ERROR (Status);

 

   Status = gDS->SetMemorySpaceAttributes (

                   Instance->DeviceBaseAddress,

                   RuntimeMmioRegionSize,

-                  EFI_MEMORY_UC | EFI_MEMORY_RUNTIME

+                  EFI_MEMORY_WC | EFI_MEMORY_RUNTIME

                   );

   ASSERT_EFI_ERROR (Status);