CNTVOFF

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:

HCR_EL2.E2H is 1, and CNTVCT_EL0 is read from EL2.
HCR_EL2.{E2H, TGE} is {1, 1}, and either:
- CNTVCT_EL0 is read from EL0 or EL2.
- CNTVCT is read from EL0.

Attributes

Field descriptions

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.

The reset behavior of this field is:

On a Warm reset, this field resets to an architecturally UNKNOWN value.

Accessing CNTVOFF_EL2

Accesses to this register use the following encodings in the System register encoding space:

MRS <Xt>, CNTVOFF_EL2

op0	op1	CRn	CRm	op2
0b11	0b100	0b1110	0b0000	0b011

if PSTATE.EL == EL0 then UNDEFINED; elsif PSTATE.EL == EL1 then if EL2Enabled() && HCR_EL2.<NV2,NV> == '11' then X[t, 64] = NVMem[0x060]; elsif EL2Enabled() && HCR_EL2.NV == '1' then AArch64.SystemAccessTrap(EL2, 0x18); else UNDEFINED; elsif PSTATE.EL == EL2 then X[t, 64] = CNTVOFF_EL2; elsif PSTATE.EL == EL3 then X[t, 64] = CNTVOFF_EL2;

MSR CNTVOFF_EL2, <Xt>

op0	op1	CRn	CRm	op2
0b11	0b100	0b1110	0b0000	0b011

if PSTATE.EL == EL0 then UNDEFINED; elsif PSTATE.EL == EL1 then if EL2Enabled() && HCR_EL2.<NV2,NV> == '11' then NVMem[0x060] = X[t, 64]; elsif EL2Enabled() && HCR_EL2.NV == '1' then AArch64.SystemAccessTrap(EL2, 0x18); else UNDEFINED; elsif PSTATE.EL == EL2 then CNTVOFF_EL2 = X[t, 64]; elsif PSTATE.EL == EL3 then CNTVOFF_EL2 = X[t, 64];

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
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
Virtual offset
Virtual offset

CNTVOFF_EL2, Counter-timer Virtual Offset Register