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] .
This register is present only when AArch32 is supported at any Exception level. Otherwise, direct accesses to CNTVOFF are UNDEFINED.
If EL2 is not implemented, this register is RES0 from EL3 and the virtual counter uses a fixed virtual offset of zero.
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.
Attributes
CNTVOFF is a 64-bit register.
Field descriptions
The CNTVOFF bit assignments are:
| 63 | 62 | 61 | 60 | 59 | 58 | 57 | 56 | 55 | 54 | 53 | 52 | 51 | 50 | 49 | 48 | 47 | 46 | 45 | 44 | 43 | 42 | 41 | 40 | 39 | 38 | 37 | 36 | 35 | 34 | 33 | 32 |
| Virtual offset | |||||||||||||||||||||||||||||||
| Virtual offset | |||||||||||||||||||||||||||||||
| 31 | 30 | 29 | 28 | 27 | 26 | 25 | 24 | 23 | 22 | 21 | 20 | 19 | 18 | 17 | 16 | 15 | 14 | 13 | 12 | 11 | 10 | 9 | 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | 0 |
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.
On a Warm reset, 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>
| coproc | CRm | opc1 |
|---|---|---|
| 0b1111 | 0b1110 | 0b0100 |
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>
| coproc | CRm | opc1 |
|---|---|---|
| 0b1111 | 0b1110 | 0b0100 |
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];