D4.3.1 VMSAv8-64 translation table level 0 level 1 and level 2 descriptor formats

In the VMSAv8-64 translation table format, the difference in the formats of the level 0, level 1 and level 2 descriptors is:

• Whether a block entry is permitted.
• If a block entry is permitted, the size of the memory region described by that entry.

These differences depend on the translation granule, as follows:
4KB granule
A level 0 descriptor does not support block translation.
A block entry:

• In a level 1 table describes the mapping of the associated 1GB input address range.
• In a level 2 table describes the mapping of the associated 2MB input address range.

16KB granule
Level 0 and level 1 descriptors do not support block translation.
A block entry in a level 2 table describes the mapping of the associated 32MB input address range.

64KB granule
Level 0 lookup is not supported.
A level 1 descriptor does not support block translation.
A block entry in a level 2 table describes the mapping of the associated 512MB input address range.

Figure D4-16 on page D4-1696 shows the ARMv8 level 0, level 1, and level 2 descriptor formats:

Descriptor encodings, ARMv8 level 0, level 1, and level 2 formats

Descriptor bit[0] identifies whether the descriptor is valid, and is 1 for a valid descriptor. If a lookup returns an invalid descriptor, the associated input address is unmapped, and any attempt to access it generates a Translation fault.
Descriptor bit[1] identifies the descriptor type, and is encoded as:

The other fields in the valid descriptors are:

Block descriptor
Gives the base address and attributes of a block of memory, as follows:

4KB translation granule

• For a level 1 Block descriptor, bits[47:30] are bits[47:30] of the output address. This output address specifies a 1GB block of memory.
• For a level 2 descriptor, bits[47:21] are bits[47:21] of the output address.This output address specifies a 2MB block of memory.

16KB translation granule
For a level 2 Block descriptor, bits[47:25] are bits[47:25] of the output address.This output address specifies a 32MB block of memory.

64KB translation granule
For a level 2 Block descriptor, bits[47:29] are bits[47:29] of the output address.This output address specifies a 512MB block of memory. Bits[63:52, 11:2] provide attributes for the target memory block, see Memory attribute fields in the VMSAv8-64 translation table format descriptors on page D4-1699. The position and contents of these bits are identical in the level 2 block descriptor and in the level 3 page descriptor.

Table descriptor
Gives the translation table address for the next-level lookup, as follows:

4KB translation granule

• Bits[47:12] are bits[47:12] of the address of the required next-level table, which is:
  • For a level 0 Table descriptor, the address of a level 1 table.
  • For a level 1Table descriptor, the address of a level 2 table.
  • For a level 2 Table descriptor, the address of a level 3 table.
• Bits[11:0] of the table address are zero.

16KB translation granule

• Bits[47:14] are bits[47:14] of the address of the required next-level table, which is:
  • For a level 0 Table descriptor, the address of a level 1 table.
  • For a level 1 Table descriptor, the address of a level 2 table.
  • For a level 2 Table descriptor, the address of a level 3 table.
• Bits[13:0] of the table address are zero.

64KB translation granule

• Bits[47:16] are bits[47:16] of the address of the required next-level table, which is:
  • For a level 1 Table descriptor, the address of a level 2 table.
  • For a level 2 Table descriptor, the address of a level 3 table.
• Bits[15:0] of the table address are zero.

For a stage 1 translation only, bits[63:59] provide attributes for the next-level lookup, see Memory attribute fields in the VMSAv8-64 translation table format descriptors on page D4-1699.

If the translation table defines the Non-secure EL1&0 stage 1 translations, then the output address in the descriptor is the IPA of the target block or table. Otherwise, it is the PA of the target block or table.