Hard Processor System Technical Reference Manual: Agilex™ 5 SoCs

ID 814346
Date 4/01/2024
Public

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3.6.3.4.1. Translation Lookaside Buffer

Translation lookaside buffer (TLB) is a cache of recently executed page translations within the MMU. The Cortex-A55 core implements a two-level TLB structure. The L2 TLB stores all page sizes and is responsible for breaking these down into smaller pages when required for the data or instruction L1 TLB.

Table 48.  MMU Components
Component Number of Entries Associativity Description
Instruction L1 TLB 15 Fully associative The first level of caching for the translation table is an L1 TLB, implemented on each of the instruction and data sides. All TLB maintenance operations affect both the L1 instruction and data TLBs and cause them to be invalidated.
Data L1 TLB 16 Fully associative
L2 TLB 1024 4-way set associative A unified L2 TLB handles any misses from the L1 instruction and data TLBs.
Walk cache RAM 64 4-way set associative The walk cache RAM holds the results of a stage 1 translation up to, but not including the last level.
IPA cache RAM 64 4-way set associative The Intermediate Physical Address (IPA) cache RAM holds mapping between the IPAs and the physical addresses. Only Non-secure EL1 and EL0 stage 2 translations use the IPA cache. When a stage 2 translation completes, the cache is updated. The IPA cache is checked whenever a stage 2 translation is required.
L2 TLB entries contain global and address space identifiers (ASID) to prevent context switch TLB flushes. The TLB entries contain a virtual machine identifier (VMID) to prevent context switch TLB flushes on virtual machine switches by the hypervisor.