ID_MMFR0, Memory Model Feature Register 0

The ID_MMFR0 characteristics are:

Purpose

Provides information about the implemented memory model and memory management support in AArch32 state.

Must be interpreted with ID_MMFR1, ID_MMFR2, ID_MMFR3, and ID_MMFR4.

For general information about the interpretation of the ID registers see 'Principles of the ID scheme for fields in ID registers'.

Configuration

AArch32 System register ID_MMFR0 bits [31:0] are architecturally mapped to AArch64 System register ID_MMFR0_EL1[31:0] .

This register is present only when AArch32 is supported at any Exception level. Otherwise, direct accesses to ID_MMFR0 are UNDEFINED.

Attributes

ID_MMFR0 is a 32-bit register.

Field descriptions

The ID_MMFR0 bit assignments are:

InnerShr, bits [31:28]

Innermost Shareability. Indicates the innermost shareability domain implemented. Defined values are:

All other values are reserved.

In Armv8-A, the permitted values are 0b0000, 0b0001, and 0b1111.

This field is valid only if the implementation supports two levels of shareability, as indicated by ID_MMFR0.ShareLvl having the value 0b0001.

When ID_MMFR0.ShareLvl is zero, this field is UNKNOWN.

FCSE, bits [27:24]

Indicates whether the implementation includes the FCSE. Defined values are:

All other values are reserved.

In Armv8-A, the only permitted value is 0b0000.

AuxReg, bits [23:20]

Auxiliary Registers. Indicates support for Auxiliary registers. Defined values are:

All other values are reserved.

In Armv8-A, the only permitted value is 0b0010.

TCM, bits [19:16]

Indicates support for TCMs and associated DMAs. Defined values are:

All other values are reserved.

In Armv8-A, the only permitted value is 0b0000.

ShareLvl, bits [15:12]

Shareability Levels. Indicates the number of shareability levels implemented. Defined values are:

All other values are reserved.

In Armv8-A, the only permitted value is 0b0001.

OuterShr, bits [11:8]

Outermost Shareability. Indicates the outermost shareability domain implemented. Defined values are:

All other values are reserved.

In Armv8-A, the permitted values are 0b0000, 0b0001, and 0b1111.

PMSA, bits [7:4]

Indicates support for a PMSA. Defined values are:

All other values are reserved.

In Armv8-A, the only permitted value is 0b0000.

VMSA, bits [3:0]

Indicates support for a VMSA. Defined values are:

All other values are reserved.

In Armv8-A, the only permitted value is 0b0101.

if PSTATE.EL == EL0 then
    UNDEFINED;
elsif PSTATE.EL == EL1 then
    if EL2Enabled() && !ELUsingAArch32(EL2) && HSTR_EL2.T0 == '1' then
        AArch64.AArch32SystemAccessTrap(EL2, 0x03);
    elsif EL2Enabled() && ELUsingAArch32(EL2) && HSTR.T0 == '1' then
        AArch32.TakeHypTrapException(0x03);
    elsif EL2Enabled() && !ELUsingAArch32(EL2) && HCR_EL2.TID3 == '1' then
        AArch64.AArch32SystemAccessTrap(EL2, 0x03);
    elsif EL2Enabled() && ELUsingAArch32(EL2) && HCR.TID3 == '1' then
        AArch32.TakeHypTrapException(0x03);
    else
        return ID_MMFR0;
elsif PSTATE.EL == EL2 then
    return ID_MMFR0;
elsif PSTATE.EL == EL3 then
    return ID_MMFR0;