Datasheet

Processor Configuration Registers
202 Datasheet, Volume 2
2.15.14 PMEM_REG—Protected Memory Enable Register
This register enables the DMA protected memory regions setup through the PLMBASE,
PLMLIMT, PHMBASE, PHMLIMIT registers. When LT.CMD.LOCK.PMRC command is
invoked, this register is locked (treated RO). When LT.CMD.UNLOCK.PMRC command is
invoked, this register is unlocked (treated RW). This register is always treated as RO
(0) for implementations not supporting protected memory regions (PLMR and PHMR
fields reported as 0 in the Capability register).
B/D/F/Type: 0/0/0/VC0PREMAP
Address Offset: 64–67h
Reset Value: 00000000h
Access: RW, RO
Bit Attr
Reset
Value
Description
31 RW 0h
Enable Protected Memory (EPM)
This field controls DMA accesses to the protected low-memory and protected
high-memory regions.
0 = DMA accesses to protected memory regions are handled as follows:
— If DMA-remapping hardware is not enabled, DMA requests
(including those to protected regions) are not blocked.
— If DMA-remapping hardware is enabled, DMA requests are
translated per the programming of the DMA-remapping
structures. Software may program the DMA-remapping structures
to allow or block DMA to the protected memory regions.
1 = DMA accesses to protected memory regions are handled as follows:
— If DMA-remapping hardware is not enabled, DMA to protected
memory regions are blocked. These DMA requests are not
recorded or reported as DMA-remapping faults.
— If DMA-remapping hardware is enabled, hardware may or may not
block DMA to the protected memory region(s). Software must not
depend on hardware protection of the protected memory regions,
and must ensure the DMA-remapping structures are properly
programmed to not allow DMA to the protected memory regions.
Hardware reports the status of the protected memory
enable/disable operation through the PRS field in this register.
Hardware implementations supporting DMA draining must drain
any in-flight translated DMA requests queued within the root
complex before indicating the protected memory region as enabled
through the PRS field.
30:1 RO
00000000
h
Reserved
0RO 0h
Protected Region Status (PRS)
This field indicates the status of protected memory region.
0 = Protected memory region(s) not enabled.
1 = Protected memory region(s) enabled.