Hard Processor System Technical Reference Manual: Agilex™ 5 SoCs

ID 814346
Date 4/01/2024
Public

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3.6.3.4.2. Translation Match Process

The Arm* v8-A architecture provides support for multiple maps from the virtual address space that are translated differently. The TLB entries store the context information that is required to facilitate a match and avoid the need for a TLB flush on a context or virtual machine switch.

Each TLB entry contains a virtual address, physical address and a set of memory properties that include type and access permissions. Each entry is either a global entry, or it is associated with a particular Address Space Identifier (ASID). In addition, each TLB entry contains a field to store the Virtual Machine Identifier (VMID) in the entry applicable to accesses from Non-secure EL0 and EL1 Exception levels.

Each entry is associated with a particular translation regime:
  • EL3 in secure state in AArch64 state only
  • EL2 (or EL0 in VHE mode) in non-secure state
  • EL1 or EL0 in secure state or EL3 in secure state in AArch32
  • EL1 or EL0 in non-secure state

A TLB match entry occurs when:

  • A virtual address matches the requested address.
  • The memory space matches the memory space state of the requests. The memory space can be one of the four states mentioned above.
  • The ASID matches the current ASID held in the CONTEXTIDR, TTBR0 or TTBR1 register, or the entry is marked global.
  • The ASID matches are ignored for requests originating from EL2 when not in VHE mode or from EL3 in AArch64.
  • The VMID matches the current VMID held in VTTBR_EL2 register.
  • The VMID match is ignored for a request not originating from Non-secure EL0 or EL1.