4.2.24. TLB Lockdown Register

The TLB Lockdown Register characteristics are:

Purpose

Controls where hardware translation table walks place the TLB entry. The TLB entry can be in either:

  • the set-associative region of the TLB.

  • the lockdown region of the TLB, and if in the lockdown region, the entry to write.

    The lockdown region of the TLB contains four entries.

Usage constraints

The TLB Lockdown Register is:

  • only accessible in privileged modes.

  • common to Secure and Non-secure states.

  • Not accessible if NSACR.TL is 0.

Configurations

Available in all configurations.

Attributes

See the register summary in Table 4.21.

Figure 4.12 shows the TLB Lockdown Register bit assignments.

Figure 4.12. TLB Lockdown Register bit assignments


Table 4.22 shows the TLB Lockdown Register bit assignments

Table 4.22. TLB Lockdown Register bit assignments

BitsNameDescription
[31:30]-UNK/SBZP
[29:28]VictimLockdown region
[27:1]-UNK/SBZP
[0]P Preserve bit. 0 is the reset value.

To access the TLB Lockdown Register use:

MRC p15, 0,<Rd>, c10, c0, 0; Read TLB Lockdown victim
MCR p15, 0,<Rd>, c10, c0, 0; Write TLB Lockdown victim

Writing the TLB Lockdown Register with the preserve bit (P bit) set to:

1

Means subsequent hardware translation table walks place the TLB entry in the lockdown region at the entry specified by the victim, in the range 0 to 3.

0

Means subsequent hardware translation table walks place the TLB entry in the set-associative region of the TLB.

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