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_EL3.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	where 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	where RW != 00	Normal memory, Outer Write-Through Transient.
0b0100		Normal memory, Outer Non-cacheable.
0b01RW	where RW != 00	Normal memory, Outer Write-Back Transient.
0b10RW		Normal memory, Outer Write-Through Non-transient.
0b11RW		Normal memory, Outer Write-Back Non-transient.

R encodes the Outer Read-Allocate policy and W encodes the Outer Write-Allocate policy.

iiii is encoded as follows:

'iiii'		Meaning
0b0000		See encoding of Attr.
0b00RW	where RW != 00	Normal memory, Inner Write-Through Transient.
0b0100		Normal memory, Inner Non-cacheable.
0b01RW	where RW != 00	Normal memory, Inner Write-Back Transient.
0b10RW		Normal memory, Inner Write-Through Non-transient.
0b11RW		Normal memory, Inner Write-Back Non-transient.

R encodes the Inner Read-Allocate policy and W encodes the Inner Write-Allocate policy.

In oooo and iiii, R and W are encoded as follows:

'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.