MAIR_EL3

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MAIR_EL3, Memory Attribute Indirection Register (EL3)

Purpose

Provides the memory attribute encodings corresponding to the possible AttrIndx values in a Long-descriptor format translation table entry for stage 1 translations at EL3.

Configuration

This register is present only when EL3 is implemented and FEAT_AA64 is implemented. Otherwise, direct accesses to MAIR_EL3 are UNDEFINED.

Attributes

Field descriptions

Attr<n>, bits [8n+7:8n], for n = 7 to 0

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.

Accessing MAIR_EL3

Accesses to this register use the following encodings in the System register encoding space:

MRS <Xt>, MAIR_EL3

op0	op1	CRn	CRm	op2
0b11	0b110	0b1010	0b0010	0b000

MSR MAIR_EL3, <Xt>

op0	op1	CRn	CRm	op2
0b11	0b110	0b1010	0b0010	0b000

if !(HaveEL(EL3) && IsFeatureImplemented(FEAT_AA64)) then Undefined(); elsif PSTATE.EL == EL0 then Undefined(); elsif PSTATE.EL == EL1 then Undefined(); elsif PSTATE.EL == EL2 then Undefined(); elsif PSTATE.EL == EL3 then if IsFeatureImplemented(FEAT_FGWTE3) && FGWTE3_EL3().MAIR_EL3 == '1' then AArch64_SystemAccessTrap(EL3, 0x18); else MAIR_EL3() = X{64}(t); end; end;

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31	30	29	28	27	26	25	24	23	22	21	20	19	18	17	16	15	14	13	12	11	10	9	8	7	6	5	4	3	2	1	0
Attr7								Attr6								Attr5								Attr4
Attr3								Attr2								Attr1								Attr0