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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>
This commit is contained in:
Ard Biesheuvel 2022-10-24 18:16:18 +02:00 committed by mergify[bot]
parent 25589c4a76
commit 789a723285
2 changed files with 4 additions and 65 deletions
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65
OvmfPkg/VirtNorFlashDxe/VirtNorFlash.c
View File

@ -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;
}

4
OvmfPkg/VirtNorFlashDxe/VirtNorFlashDxe.c
View File

@ -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);