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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:

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.

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];

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