Hard Processor System Technical Reference Manual: Agilex™ 5 SoCs

ID 814346
Date 7/19/2024
Public

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4.3.7.9. Create Context Descriptor

Context Descriptor is a data structure in system memory which defines how Stage-1 translation is performed.

Total 64-bytes of memory needs to be allocated for a CD.

Table 102.  Context Descriptor Fields
Field Description
AA64 Translation table format:
  • 0: AArch32
  • 1: AArch64
EPD0 Enable translations for TTB0 by setting EPD0 to 0.
TTB0 Base address of translation table 0.
TG0 Translation granule size for TTB0 when CD.AA64 = 1.
IR0

OR0

Cacheability attribute to use for translation table walks to TTB0.
  • 00: Non-cacheable.
  • 01: Write-back cacheable, Read-Allocate Write-Allocate.
  • 10: Write-through cacheable, Read-Allocate.
SH0 Shareability of translation table walks to TTB0.
  • 00: Non-shareable.
  • 01: Outer shareable.
  • 10 Inner shareable.
EPD1 If the StreamWorld supports split address spaces, enables table walks for TTB1.

The SMMU supports both global and context specific Bypass modes.

ENDI The endianness for the translation tables.
IPS The IPA size when CD.AA64 = 1.
ASET Defines whether the ASID values are shared with the ASID values of an Arm processor.
Note: if you expect this context to receive broadcast TLB invalidation commands from a PE, set ASET to 0.
V Valid CD. This field must be set to 1.