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CNTVOFF_EL2, Counter-timer Virtual Offset register

The CNTVOFF_EL2 characteristics are:

Purpose

Holds the 64-bit virtual offset. This is the offset between the physical count value visible in CNTPCT_EL0 and the virtual count value visible in CNTVCT_EL0.

Configuration

AArch64 System register CNTVOFF_EL2 bits [63:0] are architecturally mapped to AArch32 System register CNTVOFF[63:0] .

If EL2 is not implemented, this register is RES0 from EL3 and the virtual counter uses a fixed virtual offset of zero.

Note

When EL2 is implemented and enabled in the current Security state, and is using AArch64, the virtual counter uses a fixed virtual offset of zero in the following situations:

RW fields in this register reset to architecturally UNKNOWN values.

Attributes

CNTVOFF_EL2 is a 64-bit register.

Field descriptions

The CNTVOFF_EL2 bit assignments are:

6362616059585756555453525150494847464544434241403938373635343332
Virtual offset
Virtual offset
313029282726252423222120191817161514131211109876543210

Bits [63:0]

Virtual offset.

If the Generic counter is implemented at a size less than 64 bits, then this field is permitted to be implemented at the same width as the counter, and the upper bits are RES0.

The value of this field is treated as zero-extended in all counter calculations.

This field resets to an architecturally UNKNOWN value.

Accessing the CNTVOFF_EL2

Accesses to this register use the following encodings:

MRS <Xt>, CNTVOFF_EL2

op0op1CRnCRmop2
0b110b1000b11100b00000b011
if PSTATE.EL == EL0 then
    UNDEFINED;
elsif PSTATE.EL == EL1 then
    if EL2Enabled() && HCR_EL2.<NV2,NV> == '11' then
        return NVMem[0x060];
    elsif EL2Enabled() && HCR_EL2.NV == '1' then
        AArch64.SystemAccessTrap(EL2, 0x18);
    else
        UNDEFINED;
elsif PSTATE.EL == EL2 then
    return CNTVOFF_EL2;
elsif PSTATE.EL == EL3 then
    return CNTVOFF_EL2;
              

MSR CNTVOFF_EL2, <Xt>

op0op1CRnCRmop2
0b110b1000b11100b00000b011
if PSTATE.EL == EL0 then
    UNDEFINED;
elsif PSTATE.EL == EL1 then
    if EL2Enabled() && HCR_EL2.<NV2,NV> == '11' then
        NVMem[0x060] = X[t];
    elsif EL2Enabled() && HCR_EL2.NV == '1' then
        AArch64.SystemAccessTrap(EL2, 0x18);
    else
        UNDEFINED;
elsif PSTATE.EL == EL2 then
    CNTVOFF_EL2 = X[t];
elsif PSTATE.EL == EL3 then
    CNTVOFF_EL2 = X[t];
              


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