VDFSR, Virtual SError Exception Syndrome Register

The VDFSR characteristics are:

Purpose

Provides the syndrome value reported to software on taking a virtual SError interrupt exception to EL1, or on executing an ESB instruction at EL1.

When a virtual SError interrupt is taken, the syndrome value is reported in DFSR.{AET, ExT} and the remainder of the DFSR is set as defined by VMSAv8-32. For more information, see The AArch32 Virtual Memory System Architecture.

If the virtual SError interrupt is deferred by an ESB instruction, then the syndrome value is written to VDISR.

Configuration

AArch32 System register VDFSR bits [31:0] are architecturally mapped to AArch64 System register VSESR_EL2[31:0] when the highest implemented Exception level is using AArch64.

This register is present only when RAS is implemented. Otherwise, direct accesses to VDFSR are UNDEFINED.

If EL2 is not implemented, then VDFSR is RES0 from Monitor mode when SCR.NS == 1.

RW fields in this register reset to architecturally UNKNOWN values.

Attributes

VDFSR is a 32-bit register.

Field descriptions

The VDFSR bit assignments are:

Bits [31:16]

Reserved, RES0.

AET, bits [15:14]

When a virtual SError interrupt is taken to EL1 using AArch32, DFSR[15:4] is set to VDFSR.AET.

When a virtual SError interrupt is deferred by an ESB instruction, VDISR[15:4] is set to VDFSR.AET.

This field resets to an architecturally UNKNOWN value.

Bit [13]

Reserved, RES0.

ExT, bit [12]

When a virtual SError interrupt is taken to EL1 using AArch32, DFSR[12] is set to VDFSR.ExT.

When a virtual SError interrupt is deferred by an ESB instruction, VDISR[12] is set to VDFSR.ExT.

This field resets to an architecturally UNKNOWN value.

Bits [11:0]

Reserved, RES0.

if PSTATE.EL == EL0 then
    UNDEFINED;
elsif PSTATE.EL == EL1 then
    if EL2Enabled() && !ELUsingAArch32(EL2) && HSTR_EL2.T5 == '1' then
        AArch64.AArch32SystemAccessTrap(EL2, 0x03);
    elsif EL2Enabled() && ELUsingAArch32(EL2) && HSTR.T5 == '1' then
        AArch32.TakeHypTrapException(0x03);
    else
        UNDEFINED;
elsif PSTATE.EL == EL2 then
    return VDFSR;
elsif PSTATE.EL == EL3 then
    if SCR.NS == '0' then
        UNDEFINED;
    else
        return VDFSR;
              

if PSTATE.EL == EL0 then
    UNDEFINED;
elsif PSTATE.EL == EL1 then
    if EL2Enabled() && !ELUsingAArch32(EL2) && HSTR_EL2.T5 == '1' then
        AArch64.AArch32SystemAccessTrap(EL2, 0x03);
    elsif EL2Enabled() && ELUsingAArch32(EL2) && HSTR.T5 == '1' then
        AArch32.TakeHypTrapException(0x03);
    else
        UNDEFINED;
elsif PSTATE.EL == EL2 then
    VDFSR = R[t];
elsif PSTATE.EL == EL3 then
    if SCR.NS == '0' then
        UNDEFINED;
    else
        VDFSR = R[t];