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CNTVCT_EL0, Counter-timer Virtual Count register

The CNTVCT_EL0 characteristics are:

Purpose

Holds the 64-bit virtual count value. The virtual count value is equal to the physical count value minus the virtual offset visible in CNTVOFF_EL2.

Configuration

AArch64 System register CNTVCT_EL0 bits [63:0] are architecturally mapped to AArch32 System register CNTVCT[63:0] .

The value of this register is the same as the value of CNTPCT_EL0 in the following conditions:

  • When EL2 is not implemented.
  • When EL2 is implemented, HCR_EL2.E2H is 1, and this register is read from EL2.
  • When EL2 is implemented and enabled in the current Security state, HCR_EL2.{E2H, TGE} is {1, 1}, and this register is read from EL0 or EL2.

All reads to the CNTVCT_EL0 occur in program order relative to reads to CNTVCTSS_EL0 or CNTVCT_EL0.

Attributes

CNTVCT_EL0 is a 64-bit register.

Field descriptions

The CNTVCT_EL0 bit assignments are:

6362616059585756555453525150494847464544434241403938373635343332
Virtual count value
Virtual count value
313029282726252423222120191817161514131211109876543210

Bits [63:0]

Virtual count value.

Accessing the CNTVCT_EL0

Accesses to this register use the following encodings:

MRS <Xt>, CNTVCT_EL0

op0op1CRnCRmop2
0b110b0110b11100b00000b010
if PSTATE.EL == EL0 then
    if !ELUsingAArch32(EL1) && !(EL2Enabled() && HCR_EL2.<E2H,TGE> == '11') && CNTKCTL_EL1.EL0VCTEN == '0' then
        if EL2Enabled() && !ELUsingAArch32(EL2) && HCR_EL2.TGE == '1' then
            AArch64.SystemAccessTrap(EL2, 0x18);
        else
            AArch64.SystemAccessTrap(EL1, 0x18);
    elsif EL2Enabled() && !ELUsingAArch32(EL2) && HCR_EL2.<E2H,TGE> == '11' && CNTHCTL_EL2.EL0VCTEN == '0' then
        AArch64.SystemAccessTrap(EL2, 0x18);
    elsif !ELUsingAArch32(EL1) && !(EL2Enabled() && HCR_EL2.<E2H,TGE> == '11') && CNTHCTL_EL2.EL1TVCT == '1' then
        AArch64.SystemAccessTrap(EL2, 0x18);
    else
        return CNTVCT_EL0;
elsif PSTATE.EL == EL1 then
    if !ELUsingAArch32(EL1) && !(EL2Enabled() && HCR_EL2.<E2H,TGE> == '11') && CNTHCTL_EL2.EL1TVCT == '1' then
        AArch64.SystemAccessTrap(EL2, 0x18);
    else
        return CNTVCT_EL0;
elsif PSTATE.EL == EL2 then
    return CNTVCT_EL0;
elsif PSTATE.EL == EL3 then
    return CNTVCT_EL0;
              


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