CNTVOFF_EL2, Counter-timer Virtual Offset Register

The CNTVOFF_EL2 characteristics are:

Purpose

Holds the 64-bit virtual offset. This is the offset for the AArch64 virtual timers and counters.

Configuration

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

The virtual offset applies to:

Direct reads of CNTVCT_EL0.
Indirect reads of the virtual counter by the EL1 virtual timer. See 'The Generic Timer in AArch64 state'.
Indirect reads of the physical counter for timestamps generated by profiling logic. See 'The Statistical Profiling Extension' and 'AArch64 Self-hosted Trace'.

The virtual offset only applies under conditions described by the relevant sections.

Attributes

CNTVOFF_EL2 is a 64-bit register.

Field descriptions

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

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 EffectiveHCR_EL2_NVx() IN {'1x1'} then X[t, 64] = NVMem[0x060]; elsif EffectiveHCR_EL2_NVx() IN {'xx1'} 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 EffectiveHCR_EL2_NVx() IN {'1x1'} then NVMem[0x060] = X[t, 64]; elsif EffectiveHCR_EL2_NVx() IN {'xx1'} 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];

26/03/2024 09:49; 67c0ae5282a7629ba0ea0ba7267b43cd4f7939f6