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# VMPIDR_EL2, Virtualization Multiprocessor ID Register

The VMPIDR_EL2 characteristics are:

## Purpose

Holds the value of the Virtualization Multiprocessor ID. This is the value returned by EL1 reads of MPIDR_EL1.

## Configuration

AArch64 System register VMPIDR_EL2 bits [31:0] are architecturally mapped to AArch32 System register VMPIDR[31:0].

If EL2 is not implemented, reads of this register return the value of the MPIDR_EL1 and writes to the register are ignored.

This register has no effect if EL2 is not enabled in the current Security state.

## Attributes

VMPIDR_EL2 is a 64-bit register.

## Field descriptions

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
RES0 | Aff3
RES1 | U | RES0 | MT | Aff2 | Aff1 | Aff0

#### Bits [63:40]

Reserved, RES0.

#### Aff3, bits [39:32]

Affinity level 3. See the description of VMPIDR_EL2.Aff0 for more information.

Aff3 is not supported in AArch32 state.

The reset behavior of this field is:

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

#### Bit [31]

Reserved, RES1.

#### U, bit [30]

Indicates a Uniprocessor system, as distinct from PE 0 in a multiprocessor system.

U | Meaning
--- | ---
0b0 | Processor is part of a multiprocessor system.
0b1 | Processor is part of a uniprocessor system.

The reset behavior of this field is:

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

#### Bits [29:25]

Reserved, RES0.

#### MT, bit [24]

Indicates whether the lowest level of affinity consists of logical PEs that are implemented using a multithreading type approach. See the description of VMPIDR_EL2.Aff0 for more information about affinity levels.

MT | Meaning
--- | ---
0b0 | Performance of PEs at the lowest affinity level is largely independent.
0b1 | Performance of PEs at the lowest affinity level is very interdependent.

The reset behavior of this field is:

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

#### Aff2, bits [23:16]

Affinity level 2. See the description of VMPIDR_EL2.Aff0 for more information.

The reset behavior of this field is:

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

#### Aff1, bits [15:8]

Affinity level 1. See the description of VMPIDR_EL2.Aff0 for more information.

The reset behavior of this field is:

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

#### Aff0, bits [7:0]

Affinity level 0. This is the affinity level that is most significant for determining PE behavior. Higher affinity levels are increasingly less significant in determining PE behavior.

The assigned value of the MPIDR.{Aff2, Aff1, Aff0} or MPIDR_EL1.{Aff3, Aff2, Aff1, Aff0} set of fields of each PE must be unique within the system as a whole.

The reset behavior of this field is:

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

## Accessing VMPIDR_EL2

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

#### MRS <Xt>, VMPIDR_EL2

op0 | op1 | CRn | CRm | op2
--- | --- | --- | --- | ---
0b11 | 0b100 | 0b0000 | 0b0000 | 0b101

if PSTATE.EL == EL0 then UNDEFINED; elsif PSTATE.EL == EL1 then if EffectiveHCR_EL2_NVx() IN {'1x1'} then X[t, 64] = NVMem[0x050]; elsif EffectiveHCR_EL2_NVx() IN {'xx1'} then AArch64.SystemAccessTrap(EL2, 0x18); else UNDEFINED; elsif PSTATE.EL == EL2 then X[t, 64] = VMPIDR_EL2; elsif PSTATE.EL == EL3 then if !HaveEL(EL2) then X[t, 64] = MPIDR_EL1; else X[t, 64] = VMPIDR_EL2;

#### MSR VMPIDR_EL2, <Xt>

op0 | op1 | CRn | CRm | op2
--- | --- | --- | --- | ---
0b11 | 0b100 | 0b0000 | 0b0000 | 0b101

if PSTATE.EL == EL0 then UNDEFINED; elsif PSTATE.EL == EL1 then if EffectiveHCR_EL2_NVx() IN {'1x1'} then NVMem[0x050] = X[t, 64]; elsif EffectiveHCR_EL2_NVx() IN {'xx1'} then AArch64.SystemAccessTrap(EL2, 0x18); else UNDEFINED; elsif PSTATE.EL == EL2 then VMPIDR_EL2 = X[t, 64]; elsif PSTATE.EL == EL3 then if !HaveEL(EL2) then return; else VMPIDR_EL2 = X[t, 64];

#### MRS <Xt>, MPIDR_EL1

op0 | op1 | CRn | CRm | op2
--- | --- | --- | --- | ---
0b11 | 0b000 | 0b0000 | 0b0000 | 0b101

if PSTATE.EL == EL0 then if IsFeatureImplemented(FEAT_IDST) then if EL2Enabled() && HCR_EL2.TGE == '1' then AArch64.SystemAccessTrap(EL2, 0x18); else AArch64.SystemAccessTrap(EL1, 0x18); else UNDEFINED; elsif PSTATE.EL == EL1 then if EL2Enabled() && IsFeatureImplemented(FEAT_FGT) && (!HaveEL(EL3) || SCR_EL3.FGTEn == '1') && HFGRTR_EL2.MPIDR_EL1 == '1' then AArch64.SystemAccessTrap(EL2, 0x18); elsif EL2Enabled() then X[t, 64] = VMPIDR_EL2; else X[t, 64] = MPIDR_EL1; elsif PSTATE.EL == EL2 then X[t, 64] = MPIDR_EL1; elsif PSTATE.EL == EL3 then X[t, 64] = MPIDR_EL1;

AArch32 Registers | AArch64 Registers | AArch32 Instructions | AArch64 Instructions | Index by Encoding | External Registers | External Registers by Offset | Registers by Functional Group | Proprietary Notice

26/03/2024 09:49; 67c0ae5282a7629ba0ea0ba7267b43cd4f7939f6

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