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HTPIDR, Hyp Software Thread ID Register

The HTPIDR characteristics are:

Purpose

Provides a location where software running in Hyp mode can store thread identifying information that is not visible to Non-secure software executing at EL0 or EL1, for hypervisor management purposes.

The PE makes no use of this register.

Configuration

AArch32 System register HTPIDR bits [31:0] are architecturally mapped to AArch64 System register TPIDR_EL2[31:0] .

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

If EL2 is not implemented, this register is RES0 from EL3.

Note

The PE never updates this register.

Attributes

HTPIDR is a 32-bit register.

Field descriptions

The HTPIDR bit assignments are:

313029282726252423222120191817161514131211109876543210
Thread ID

Bits [31:0]

Thread ID. Thread identifying information stored by software running at this Exception level.

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

Accessing the HTPIDR

Accesses to this register use the following encodings:

MRC{<c>}{<q>} <coproc>, {#}<opc1>, <Rt>, <CRn>, <CRm>{, {#}<opc2>}

coprocopc1CRnCRmopc2
0b11110b1000b11010b00000b010
if PSTATE.EL == EL0 then
    UNDEFINED;
elsif PSTATE.EL == EL1 then
    if EL2Enabled() && !ELUsingAArch32(EL2) && HSTR_EL2.T13 == '1' then
        AArch64.AArch32SystemAccessTrap(EL2, 0x03);
    elsif EL2Enabled() && ELUsingAArch32(EL2) && HSTR.T13 == '1' then
        AArch32.TakeHypTrapException(0x03);
    else
        UNDEFINED;
elsif PSTATE.EL == EL2 then
    return HTPIDR;
elsif PSTATE.EL == EL3 then
    if SCR.NS == '0' then
        UNDEFINED;
    else
        return HTPIDR;
              

MCR{<c>}{<q>} <coproc>, {#}<opc1>, <Rt>, <CRn>, <CRm>{, {#}<opc2>}

coprocopc1CRnCRmopc2
0b11110b1000b11010b00000b010
if PSTATE.EL == EL0 then
    UNDEFINED;
elsif PSTATE.EL == EL1 then
    if EL2Enabled() && !ELUsingAArch32(EL2) && HSTR_EL2.T13 == '1' then
        AArch64.AArch32SystemAccessTrap(EL2, 0x03);
    elsif EL2Enabled() && ELUsingAArch32(EL2) && HSTR.T13 == '1' then
        AArch32.TakeHypTrapException(0x03);
    else
        UNDEFINED;
elsif PSTATE.EL == EL2 then
    HTPIDR = R[t];
elsif PSTATE.EL == EL3 then
    if SCR.NS == '0' then
        UNDEFINED;
    else
        HTPIDR = R[t];