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ArmVirtPkg/QemuFwCfgLib: implement QemuFwCfgSkipBytes() API 

We are now sufficiently equipped to implement the new QemuFwCfgSkipBytes()
API.

The previous patch and this one enable ArmVirtPkg/QemuFwCfgLib to
overwrite part of a writeable fw_cfg file, which will be particularly
useful for the upcoming QEMU_LOADER_WRITE_POINTER command in
OvmfPkg/AcpiPlatformDxe.

Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Ref: https://bugzilla.tianocore.org/show_bug.cgi?id=359
Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Laszlo Ersek <lersek@redhat.com>
Reviewed-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Reviewed-by: Jordan Justen <jordan.l.justen@intel.com>
This commit is contained in:
Laszlo Ersek 2017-01-27 08:10:15 +01:00
parent e8ae381f60
commit 7fcb735412
1 changed files with 78 additions and 0 deletions
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78
ArmVirtPkg/Library/QemuFwCfgLib/QemuFwCfgLib.c
View File

@ -55,19 +55,33 @@ VOID (EFIAPI WRITE_BYTES_FUNCTION) (
IN VOID *Buffer OPTIONAL
);
/**
Skips bytes in firmware configuration
@param[in] Size Size in bytes to skip
**/
typedef
VOID (EFIAPI SKIP_BYTES_FUNCTION) (
IN UINTN Size
);
//
// Forward declaration of the two implementations we have.
//
STATIC READ_BYTES_FUNCTION MmioReadBytes;
STATIC WRITE_BYTES_FUNCTION MmioWriteBytes;
STATIC SKIP_BYTES_FUNCTION MmioSkipBytes;
STATIC READ_BYTES_FUNCTION DmaReadBytes;
STATIC WRITE_BYTES_FUNCTION DmaWriteBytes;
STATIC SKIP_BYTES_FUNCTION DmaSkipBytes;
//
// These correspond to the implementation we detect at runtime.
//
STATIC READ_BYTES_FUNCTION *InternalQemuFwCfgReadBytes = MmioReadBytes;
STATIC WRITE_BYTES_FUNCTION *InternalQemuFwCfgWriteBytes = MmioWriteBytes;
STATIC SKIP_BYTES_FUNCTION *InternalQemuFwCfgSkipBytes = MmioSkipBytes;
/**
@ -183,6 +197,7 @@ QemuFwCfgInitialize (
mFwCfgDmaAddress = FwCfgDmaAddress;
InternalQemuFwCfgReadBytes = DmaReadBytes;
InternalQemuFwCfgWriteBytes = DmaWriteBytes;
InternalQemuFwCfgSkipBytes = DmaSkipBytes;
}
}
} else {
@ -433,6 +448,69 @@ QemuFwCfgWriteBytes (
}
/**
Slow SKIP_BYTES_FUNCTION.
**/
STATIC
VOID
EFIAPI
MmioSkipBytes (
IN UINTN Size
)
{
UINTN ChunkSize;
UINT8 SkipBuffer[256];
//
// Emulate the skip by reading data in chunks, and throwing it away. The
// implementation below doesn't affect the static data footprint for client
// modules. Large skips are not expected, therefore this fallback is not
// performance critical. The size of SkipBuffer is thought not to exert a
// large pressure on the stack.
//
while (Size > 0) {
ChunkSize = MIN (Size, sizeof SkipBuffer);
MmioReadBytes (ChunkSize, SkipBuffer);
Size -= ChunkSize;
}
}
/**
Fast SKIP_BYTES_FUNCTION.
**/
STATIC
VOID
EFIAPI
DmaSkipBytes (
IN UINTN Size
)
{
DmaTransferBytes (Size, NULL, FW_CFG_DMA_CTL_SKIP);
}
/**
Skip bytes in the firmware configuration item.
Increase the offset of the firmware configuration item without transferring
bytes between the item and a caller-provided buffer. Subsequent read, write
or skip operations will commence at the increased offset.
@param[in] Size Number of bytes to skip.
**/
VOID
EFIAPI
QemuFwCfgSkipBytes (
IN UINTN Size
)
{
if (QemuFwCfgIsAvailable ()) {
InternalQemuFwCfgSkipBytes (Size);
}
}
/**
Reads a UINT8 firmware configuration value