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CNTVOFF, Counter-timer Virtual Offset register

The CNTVOFF characteristics are:

Purpose

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

Configuration

AArch32 System register CNTVOFF bits [63:0] are architecturally mapped to AArch64 System register CNTVOFF_EL2[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 is using AArch64, if HCR_EL2.{E2H, TGE} is {1, 1}, the virtual counter uses a fixed virtual offset of zero when CNTVCT is read from Non-secure EL0.

When EL2 is implemented and can use AArch32, on a reset into an Exception level that is using AArch32 this register resets to an IMPLEMENTATION DEFINED value that might be UNKNOWN.

Attributes

CNTVOFF is a 64-bit register.

Field descriptions

The CNTVOFF 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

Accesses to this register use the following encodings:

MRRC{<c>}{<q>} <coproc>, {#}<opc1>, <Rt>, <Rt2>, <CRm>

coprocCRmopc1
0b11110b11100b0100
if PSTATE.EL == EL0 then
    UNDEFINED;
elsif PSTATE.EL == EL1 then
    UNDEFINED;
elsif PSTATE.EL == EL2 then
    return CNTVOFF;
elsif PSTATE.EL == EL3 then
    return CNTVOFF;
              

MCRR{<c>}{<q>} <coproc>, {#}<opc1>, <Rt>, <Rt2>, <CRm>

coprocCRmopc1
0b11110b11100b0100
if PSTATE.EL == EL0 then
    UNDEFINED;
elsif PSTATE.EL == EL1 then
    UNDEFINED;
elsif PSTATE.EL == EL2 then
    CNTVOFF = R[t2]:R[t];
elsif PSTATE.EL == EL3 then
    CNTVOFF = R[t2]:R[t];
              


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