MAIR_EL3, Memory Attribute Indirection Register (EL3)

Memory Attribute encoding.

When FEAT_AIE is implemented and stage 1 Attributes Index Extension is enabled and AttrIndx[3] in a Long descriptor format translation table entry is 0, or when FEAT_AIE is not implemented, AttrIndx[2:0] gives the value of <n> in Attr<n>.

When FEAT_AIE is implemented and stage 1 Attributes Index Extension is enabled and AttrIndx[3] in a Long descriptor format translation table entry is 1, see MAIR2_ELx.Attr

Attr is encoded as follows:

Attr	Meaning
0b0000dd00	Device memory. See encoding of 'dd' for the type of Device memory.
0b0000dd01	If FEAT_XS is implemented: Device memory with the XS attribute set to 0. See encoding of 'dd' for the type of Device memory. Otherwise, UNPREDICTABLE.
0b0000dd1x	UNPREDICTABLE.
0booooiiii, (oooo != 0000 and iiii != 0000)	Normal memory. See encoding of 'oooo' and 'iiii' for the type of Normal Memory.
0b01000000	If FEAT_XS is implemented: Normal Inner Non-cacheable, Outer Non-cacheable memory with the XS attribute set to 0. Otherwise, UNPREDICTABLE.
0b10100000	If FEAT_XS is implemented: Normal Inner Write-through Cacheable, Outer Write-through Cacheable, Read-Allocate, No-Write Allocate, Non-transient memory with the XS attribute set to 0. Otherwise, UNPREDICTABLE.
0b11110000	If FEAT_MTE2 is implemented: Tagged Normal Inner Write-Back, Outer Write-Back, Read-Allocate, Write-Allocate Non-transient memory. Otherwise, UNPREDICTABLE.
0bxxxx0000, where xxxx != 0000 and xxxx != 0100 and xxxx != 1010 and xxxx != 1111	UNPREDICTABLE.

'dd' is encoded as follows:

dd	Meaning
0b00	Device-nGnRnE memory
0b01	Device-nGnRE memory
0b10	Device-nGRE memory
0b11	Device-GRE memory

'oooo' is encoded as follows:

'oooo'	Meaning
0b0000	See encoding of Attr
0b00RW, RW not 0b00	Normal memory, Outer Write-Through Transient
0b0100	Normal memory, Outer Non-cacheable
0b01RW, RW not 0b00	Normal memory, Outer Write-Back Transient
0b10RW	Normal memory, Outer Write-Through Non-transient
0b11RW	Normal memory, Outer Write-Back Non-transient

R = Outer Read-Allocate policy, W = Outer Write-Allocate policy.

'iiii' is encoded as follows:

'iiii'	Meaning
0b0000	See encoding of Attr
0b00RW, RW not 0b00	Normal memory, Inner Write-Through Transient
0b0100	Normal memory, Inner Non-cacheable
0b01RW, RW not 0b00	Normal memory, Inner Write-Back Transient
0b10RW	Normal memory, Inner Write-Through Non-transient
0b11RW	Normal memory, Inner Write-Back Non-transient

R = Inner Read-Allocate policy, W = Inner Write-Allocate policy.

The R and W bits in 'oooo' and 'iiii' fields have the following meanings:

R or W	Meaning
0b0	No Allocate
0b1	Allocate

When FEAT_XS is implemented, stage 1 Inner Write-Back Cacheable, Outer Write-Back Cacheable memory types have the XS attribute set to 0.

The reset behavior of this field is:

• On a Warm reset, this field resets to an architecturally UNKNOWN value.