MAIR_EL1

Provides the memory attribute encodings corresponding to the possible AttrIndx values in a Long-descriptor format translation table entry for stage 1 translations at EL1.

Configuration

AArch64 System register MAIR_EL1 bits [31:0] are architecturally mapped to AArch32 System register PRRR[31:0] when TTBCR.EAE == 0.

AArch64 System register MAIR_EL1 bits [31:0] are architecturally mapped to AArch32 System register MAIR0[31:0] when TTBCR.EAE == 1.

AArch64 System register MAIR_EL1 bits [63:32] are architecturally mapped to AArch32 System register NMRR[31:0] when TTBCR.EAE == 0.

AArch64 System register MAIR_EL1 bits [63:32] are architecturally mapped to AArch32 System register MAIR1[31:0] when TTBCR.EAE == 1.

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_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.

Accessing MAIR_EL1

When the Effective value of HCR_EL2.E2H is 1, without explicit synchronization, accesses from EL3 using the accessor name MAIR_EL1 or MAIR_EL12 are not guaranteed to be ordered with respect to accesses using the other accessor name.

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

MRS <Xt>, MAIR_EL1

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

if PSTATE.EL == EL0 then UNDEFINED; elsif PSTATE.EL == EL1 then if EL2Enabled() && HCR_EL2.TRVM == '1' then AArch64.SystemAccessTrap(EL2, 0x18); elsif EL2Enabled() && IsFeatureImplemented(FEAT_FGT) && (!HaveEL(EL3) || SCR_EL3.FGTEn == '1') && HFGRTR_EL2.MAIR_EL1 == '1' then AArch64.SystemAccessTrap(EL2, 0x18); elsif EffectiveHCR_EL2_NVx() IN {'111'} then X[t, 64] = NVMem[0x140]; else X[t, 64] = MAIR_EL1; elsif PSTATE.EL == EL2 then if ELIsInHost(EL2) then X[t, 64] = MAIR_EL2; else X[t, 64] = MAIR_EL1; elsif PSTATE.EL == EL3 then X[t, 64] = MAIR_EL1;

MSR MAIR_EL1, <Xt>

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

if PSTATE.EL == EL0 then UNDEFINED; elsif PSTATE.EL == EL1 then if EL2Enabled() && HCR_EL2.TVM == '1' then AArch64.SystemAccessTrap(EL2, 0x18); elsif EL2Enabled() && IsFeatureImplemented(FEAT_FGT) && (!HaveEL(EL3) || SCR_EL3.FGTEn == '1') && HFGWTR_EL2.MAIR_EL1 == '1' then AArch64.SystemAccessTrap(EL2, 0x18); elsif EffectiveHCR_EL2_NVx() IN {'111'} then NVMem[0x140] = X[t, 64]; else MAIR_EL1 = X[t, 64]; elsif PSTATE.EL == EL2 then if ELIsInHost(EL2) then MAIR_EL2 = X[t, 64]; else MAIR_EL1 = X[t, 64]; elsif PSTATE.EL == EL3 then MAIR_EL1 = X[t, 64];

MRS <Xt>, MAIR_EL12

op0	op1	CRn	CRm	op2
0b11	0b101	0b1010	0b0010	0b000

if PSTATE.EL == EL0 then UNDEFINED; elsif PSTATE.EL == EL1 then if EffectiveHCR_EL2_NVx() == '101' then X[t, 64] = NVMem[0x140]; elsif EffectiveHCR_EL2_NVx() IN {'xx1'} then AArch64.SystemAccessTrap(EL2, 0x18); else UNDEFINED; elsif PSTATE.EL == EL2 then if ELIsInHost(EL2) then X[t, 64] = MAIR_EL1; else UNDEFINED; elsif PSTATE.EL == EL3 then if ELIsInHost(EL2) then X[t, 64] = MAIR_EL1; else UNDEFINED;

MSR MAIR_EL12, <Xt>

op0	op1	CRn	CRm	op2
0b11	0b101	0b1010	0b0010	0b000

if PSTATE.EL == EL0 then UNDEFINED; elsif PSTATE.EL == EL1 then if EffectiveHCR_EL2_NVx() == '101' then NVMem[0x140] = X[t, 64]; elsif EffectiveHCR_EL2_NVx() IN {'xx1'} then AArch64.SystemAccessTrap(EL2, 0x18); else UNDEFINED; elsif PSTATE.EL == EL2 then if ELIsInHost(EL2) then MAIR_EL1 = X[t, 64]; else UNDEFINED; elsif PSTATE.EL == EL3 then if ELIsInHost(EL2) then MAIR_EL1 = X[t, 64]; else UNDEFINED;

63	62	61	60	59	58	57	56	55	54	53	52	51	50	49	48	47	46	45	44	43	42	41	40	39	38	37	36	35	34	33	32
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

MAIR_EL1, Memory Attribute Indirection Register (EL1)

Purpose