Level 1 Memory System
ARM DDI 0500D
Copyright © 2013-2014 ARM. All rights reserved.
6-20
ID021414
Non-Confidential
Walk cache RAM
The walk cache RAM uses 117-bit encoding when parity is enabled and 114-bit encoding when
parity is disabled.
Table 6-15
shows the data fields in the walk cache descriptor.
[1:0]
Device
Shareability
00
Non-shareable.
01
Unused.
10
Outer shareable.
11
Inner shareable.
Non-coherent, Outer WB
Non-coherent, Outer NC
Non-coherent, Outer WT
Coherent, Inner WB and Outer WB
Table 6-14 Main TLB memory types and shareability (continued)
Bits
Memory type
Description
Table 6-15 Walk cache descriptor fields
Bits
Name
Description
[116:114]
ECC
ECC. If ECC is not configured, these bits are absent.
[113:84]
PA
Physical Address of second, last translation level.
[83:60]
VA
Virtual address.
[59:56]
-
Reserved, must be zero.
[55:40]
ASID
Address Space Identifier.
[39:22]
VMID
Virtual Machine Identifier.
[31]
NS, walk
Security state that the entry was fetched in.
[30:22]
-
Reserved, must be zero.
[21:18]
Domain
Valid only if the entry was fetched in VMSAv7 format.
[17:16]
Entry size
Memory size to which entry maps:
0b00
1MB.
0b01
2MB.
0b10
512MB.
0b11
Unused.
[15]
NSTable
Combined NSTable bits from first and second level stage 1 tables or NS descriptor (VMSA).
[14]
PXNTable
Combined PXNTable bits from stage1 descriptors up to last level.
[13]
XNTable
Combined XNTable bit from stage1 descriptors up to last level.
[12:11]
APTable
Combined APTable bits from stage1 descriptors up to last level.
[10]
EL3
Set if the entry was fetched in AArch64 EL3 mode.
[9]
EL2
Set if the entry was fetched in EL2 mode.
[8:1]
Attrs
Physical attributes of the final level stage 1 table.
[0]
Valid
Valid bit:
0
Entry does not contain valid data.
1
Entry contains valid data.