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CP15DMB, Data Memory Barrier System instruction

The CP15DMB characteristics are:

Purpose

Performs a Data Memory Barrier.

Arm deprecates any use of this System instruction, and strongly recommends that software use the DMB instruction instead.

Configuration

This instruction is present only when AArch32 is supported at any Exception level. Otherwise, direct accesses to CP15DMB are UNKNOWN.

Attributes

CP15DMB is a 32-bit System instruction.

Field descriptions

CP15DMB ignores the value in the register specified by the instruction encoding. Software does not have to write a value to the register before issuing this instruction.

Executing the CP15DMB instruction

Accesses to this instruction use the following encodings:

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

coprocopc1CRnCRmopc2
0b11110b0000b01110b10100b101
if PSTATE.EL == EL0 then
    if !ELUsingAArch32(EL1) && !(EL2Enabled() && HCR_EL2.<E2H,TGE> == '11') && SCTLR_EL1.CP15BEN == '0' then
        UNDEFINED;
    elsif EL2Enabled() && !ELUsingAArch32(EL2) && HCR_EL2.<E2H,TGE> == '11' && SCTLR_EL2.CP15BEN == '0' then
        UNDEFINED;
    elsif ELUsingAArch32(EL1) && SCTLR.CP15BEN == '0' then
        UNDEFINED;
    elsif EL2Enabled() && !ELUsingAArch32(EL2) && HCR_EL2.<E2H,TGE> != '11' && HSTR_EL2.T7 == '1' then
        AArch64.AArch32SystemAccessTrap(EL2, 0x03);
    elsif EL2Enabled() && ELUsingAArch32(EL2) && HSTR.T7 == '1' then
        AArch32.TakeHypTrapException(0x03);
    else
        CP15DMB();
elsif PSTATE.EL == EL1 then
    if EL2Enabled() && !ELUsingAArch32(EL2) && HSTR_EL2.T7 == '1' then
        AArch64.AArch32SystemAccessTrap(EL2, 0x03);
    elsif EL2Enabled() && ELUsingAArch32(EL2) && HSTR.T7 == '1' then
        AArch32.TakeHypTrapException(0x03);
    elsif ELUsingAArch32(EL1) && SCTLR.CP15BEN == '0' then
        UNDEFINED;
    else
        CP15DMB();
elsif PSTATE.EL == EL2 then
    if HSCTLR.CP15BEN == '0' then
        UNDEFINED;
    else
        CP15DMB();
elsif PSTATE.EL == EL3 then
    CP15DMB();