Datasheet

Processor Configuration Registers
262 Datasheet, Volume 2
30 W 0b
Set Root Table Pointer (SRTP)
Software sets this field to set/update the root-entry table pointer used by
hardware. The root-entry table pointer is specified through the Root-entry
Table Address register.
Hardware reports the status of the “root table pointer set” operation through
the RTPS field in the Global Status register.
The root table pointer set operation must be performed before enabling or
re-enabling (after disabling) DMA remapping through the TE field.
After a “root table pointer set” operation, software must globally invalidate
the context cache and then globally invalidate the IOTLB. This is required to
ensure hardware uses only the remapping structures referenced by the new
root table pointer, and not any stale cached entries.
While DMA remapping is active, software may update the root table pointer
through this field. However, to ensure valid in-flight DMA requests are
deterministically remapped, software must ensure that the structures
referenced by the new root table pointer are programmed to provide the
same remapping results as the structures referenced by the previous root-
table pointer.
Clearing this bit has no effect. The value returned on a read of this field is
undefined.
29 RO 0b
Set Fault Log (SFL)
This field is valid only for implementations supporting advanced fault logging.
Software sets this field to request hardware to set/update the fault-log
pointer used by hardware.
The fault-log pointer is specified through Advanced Fault Log register.
Hardware reports the status of the fault log set operation through the FLS
field in the Global Status register.
The fault log pointer must be set before enabling advanced fault logging
(through EAFL field). Once advanced fault logging is enabled, the fault log
pointer may be updated through this field while DMA remapping is active.
Clearing this bit has no effect.
The value returned on read of this field is undefined.
28 RO 0b
Enable Advanced Fault Logging (EAFL)
This field is valid only for implementations supporting advanced fault logging.
Software writes to this field to request hardware to enable or disable
advanced fault logging.
0 = Disable advanced fault logging. In this case, translation faults are
reported through the Fault Recording registers.
1 = Enable use of memory-resident fault log.
When enabled, translation faults are recorded in the memory-resident log.
The fault log pointer must be set in hardware (through SFL field) before
enabling advanced fault logging.
Hardware reports the status of the advanced fault logging enable operation
through the AFLS field in the Global Status register.
Value returned on read of this field is undefined.
27 W 0b
Write Buffer Flush (WBF)
This bit is valid only for implementations requiring write buffer flushing.
Software sets this field to request hardware to flush the root-complex
internal write buffers. This is done to ensure any updates to the memory-
resident remapping structures are not held in any internal write posting
buffers.
Refer to the VTd specification for details on write-buffer flushing
requirements.
Hardware reports the status of the write buffer flushing operation through
the WBFS field in the Global Status register.
Clearing this bit has no effect.
Value returned on read of this field is undefined.
B/D/F/Type: 0/2/0/GFXVTBAR
Address Offset: 18–1Bh
Reset Value: 00000000h
Access: W, RO, RW
Bit Attr
Reset
Value
Description