ID_PFR1_EL1, AArch32 Processor Feature Register 1

The ID_PFR1_EL1 characteristics are:

Purpose

Gives information about the AArch32 programmers' model.

Must be interpreted with ID_PFR0_EL1.

For general information about the interpretation of the ID registers see 'Principles of the ID scheme for fields in ID registers' in the Arm® Architecture Reference Manual, Armv8, for Armv8-A architecture profile, section D10.4.1.

Configuration

AArch64 System register ID_PFR1_EL1 bits [31:0] are architecturally mapped to AArch32 System register ID_PFR1[31:0] .

In an implementation that supports only AArch64 state, this register is UNKNOWN.

Attributes

ID_PFR1_EL1 is a 64-bit register.

Field descriptions

The ID_PFR1_EL1 bit assignments are:

Bits [63:32]

Reserved, RES0.

GIC, bits [31:28]

System register GIC CPU interface. Defined values are:

All other values are reserved.

Virt_frac, bits [27:24]

Virtualization fractional field. When the Virtualization field is 0b0000, determines the support for features from the ARMv7 Virtualization Extensions. Defined values are:

All other values are reserved.

In Armv8-A the permitted values are:

• 0b0000 when EL2 is implemented.
• 0b0001 when EL2 is not implemented.

This field is only valid when the value of ID_PFR1_EL1.Virtualization is 0, otherwise it holds the value 0b0000.

Sec_frac, bits [23:20]

Security fractional field. When the Security field is 0b0000, determines the support for features from the ARMv7 Security Extensions. Defined values are:

All other values are reserved.

In Armv8-A the permitted values are:

• 0b0000 when EL3 is implemented.
• 0b0001 or 0b0010 when EL3 is not implemented.

This field is only valid when the value of ID_PFR1_EL1.Security is 0, otherwise it holds the value 0b0000.

GenTimer, bits [19:16]

Generic Timer support. Defined values are:

All other values are reserved.

ARMv8.6-ECV implements the functionality identified by the value 0b0010.

In Armv8.0, Armv8.1, Armv8.2, Armv8.3, Armv8.4, and Armv8.5, the only permitted value is 0b0001.

From Armv8.6, the only permitted value is 0b0010.

Virtualization, bits [15:12]

Virtualization support. Defined values are:

All other values are reserved.

In Armv8-A the permitted values are:

• 0b0000 when EL2 is not implemented.
• 0b0001 when EL2 is implemented.

In an implementation that includes EL2, if EL2 cannot use AArch32 but EL1 can use AArch32 then this field has the value 0b0001.

If EL1 cannot use AArch32 then this field has the value 0b0000.

MProgMod, bits [11:8]

M profile programmers' model support. Defined values are:

All other values are reserved.

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

Security, bits [7:4]

Security support. Defined values are:

All other values are reserved.

In Armv8-A the permitted values are:

• 0b0000 when EL3 is not implemented.
• 0b0001 when EL3 is implemented.

In an implementation that includes EL3, if EL3 cannot use AArch32 but EL1 can use AArch32 then this field has the value 0b0001.

If EL1 cannot use AArch32 then this field has the value 0b0000.

ProgMod, bits [3:0]

Support for the standard programmers' model for Armv4 and later. Model must support User, FIQ, IRQ, Supervisor, Abort, Undefined, and System modes. Defined values are:

All other values are reserved.

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

If EL1 cannot use AArch32 then this field has the value 0b0000.

if PSTATE.EL == EL0 then
    if IsFeatureImplemented("ARMv8.4-IDST") then
        if EL2Enabled() && !ELUsingAArch32(EL2) && HCR_EL2.TGE == '1' then
            AArch64.SystemAccessTrap(EL2, 0x18);
        else
            AArch64.SystemAccessTrap(EL1, 0x18);
    else
        UNDEFINED;
elsif PSTATE.EL == EL1 then
    if EL2Enabled() && !ELUsingAArch32(EL2) && HCR_EL2.TID3 == '1' then
        AArch64.SystemAccessTrap(EL2, 0x18);
    else
        return ID_PFR1_EL1;
elsif PSTATE.EL == EL2 then
    return ID_PFR1_EL1;
elsif PSTATE.EL == EL3 then
    return ID_PFR1_EL1;