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# CNTV_TVAL_EL0, Counter-timer Virtual Timer TimerValue Register

The CNTV_TVAL_EL0 characteristics are:

## Purpose

Holds the timer value for the EL1 virtual timer.

## Configuration

AArch64 System register CNTV_TVAL_EL0 bits [31:0] are architecturally mapped to AArch32 System register CNTV_TVAL[31:0].

## Attributes

CNTV_TVAL_EL0 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
RES0
TimerValue

#### Bits [63:32]

Reserved, RES0.

#### TimerValue, bits [31:0]

The TimerValue view of the EL1 virtual timer.

On a read of this register:

- If CNTV_CTL_EL0.ENABLE is 0, the value returned is UNKNOWN.
- If CNTV_CTL_EL0.ENABLE is 1, the value returned is (CNTV_CVAL_EL0 - CNTVCT_EL0).

On a write of this register, CNTV_CVAL_EL0 is set to (CNTVCT_EL0 + TimerValue), where TimerValue is treated as a signed 32-bit integer.

When CNTV_CTL_EL0.ENABLE is 1, the timer condition is met when (CNTVCT_EL0 - CNTV_CVAL_EL0) is greater than or equal to zero. This means that TimerValue acts like a 32-bit downcounter timer. When the timer condition is met:

- CNTV_CTL_EL0.ISTATUS is set to 1.
- If CNTV_CTL_EL0.IMASK is 0, an interrupt is generated.

When CNTV_CTL_EL0.ENABLE is 0, the TimerValue cannot be read but continues to decrement. When the timer is enabled, the TimerValue represents the elapsed time whether that time was spent enabled or disabled.

The reset behavior of this field is:

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

## Accessing CNTV_TVAL_EL0

When the Effective value of HCR_EL2.E2H is 1, without explicit synchronization, accesses from EL3 using the accessor name CNTV_TVAL_EL0 or CNTV_TVAL_EL02 are not guaranteed to be ordered with respect to accesses using the other accessor name.

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

#### MRS <Xt>, CNTV_TVAL_EL0

op0 | op1 | CRn | CRm | op2
--- | --- | --- | --- | ---
0b11 | 0b011 | 0b1110 | 0b0011 | 0b000

if PSTATE.EL == EL0 then if !ELIsInHost(EL0) && CNTKCTL_EL1.EL0VTEN == '0' then if EL2Enabled() && HCR_EL2.TGE == '1' then AArch64.SystemAccessTrap(EL2, 0x18); else AArch64.SystemAccessTrap(EL1, 0x18); elsif ELIsInHost(EL0) && CNTHCTL_EL2.EL0VTEN == '0' then AArch64.SystemAccessTrap(EL2, 0x18); elsif EL2Enabled() && !ELIsInHost(EL0) && IsFeatureImplemented(FEAT_ECV) && CNTHCTL_EL2.EL1TVT == '1' then AArch64.SystemAccessTrap(EL2, 0x18); elsif ELIsInHost(EL0) && IsCurrentSecurityState(SS_Secure) && IsFeatureImplemented(FEAT_SEL2) then if CNTHVS_CTL_EL2.ENABLE == '0' then X[t, 64] = bits(64) UNKNOWN; else X[t, 64] = CNTHVS_CVAL_EL2 - PhysicalCountInt(); elsif ELIsInHost(EL0) && !IsCurrentSecurityState(SS_Secure) then if CNTHV_CTL_EL2.ENABLE == '0' then X[t, 64] = bits(64) UNKNOWN; else X[t, 64] = CNTHV_CVAL_EL2 - PhysicalCountInt(); elsif HaveEL(EL2) && (!EL2Enabled() || !ELIsInHost(EL0)) then if CNTV_CTL_EL0.ENABLE == '0' then X[t, 64] = bits(64) UNKNOWN; else X[t, 64] = CNTV_CVAL_EL0 - (PhysicalCountInt() - CNTVOFF_EL2); else if CNTV_CTL_EL0.ENABLE == '0' then X[t, 64] = bits(64) UNKNOWN; else X[t, 64] = CNTV_CVAL_EL0 - PhysicalCountInt(); elsif PSTATE.EL == EL1 then if EL2Enabled() && IsFeatureImplemented(FEAT_ECV) && CNTHCTL_EL2.EL1TVT == '1' then AArch64.SystemAccessTrap(EL2, 0x18); elsif HaveEL(EL2) then if CNTV_CTL_EL0.ENABLE == '0' then X[t, 64] = bits(64) UNKNOWN; else X[t, 64] = CNTV_CVAL_EL0 - (PhysicalCountInt() - CNTVOFF_EL2); else if CNTV_CTL_EL0.ENABLE == '0' then X[t, 64] = bits(64) UNKNOWN; else X[t, 64] = CNTV_CVAL_EL0 - PhysicalCountInt(); elsif PSTATE.EL == EL2 then if ELIsInHost(EL2) && IsCurrentSecurityState(SS_Secure) && IsFeatureImplemented(FEAT_SEL2) then if CNTHVS_CTL_EL2.ENABLE == '0' then X[t, 64] = bits(64) UNKNOWN; else X[t, 64] = CNTHVS_CVAL_EL2 - PhysicalCountInt(); elsif ELIsInHost(EL2) && !IsCurrentSecurityState(SS_Secure) then if CNTHV_CTL_EL2.ENABLE == '0' then X[t, 64] = bits(64) UNKNOWN; else X[t, 64] = CNTHV_CVAL_EL2 - PhysicalCountInt(); elsif !ELIsInHost(EL2) then if CNTV_CTL_EL0.ENABLE == '0' then X[t, 64] = bits(64) UNKNOWN; else X[t, 64] = CNTV_CVAL_EL0 - (PhysicalCountInt() - CNTVOFF_EL2); else if CNTV_CTL_EL0.ENABLE == '0' then X[t, 64] = bits(64) UNKNOWN; else X[t, 64] = CNTV_CVAL_EL0 - PhysicalCountInt(); elsif PSTATE.EL == EL3 then if CNTV_CTL_EL0.ENABLE == '0' then X[t, 64] = bits(64) UNKNOWN; elsif HaveEL(EL2) && !ELUsingAArch32(EL2) then X[t, 64] = CNTV_CVAL_EL0 - (PhysicalCountInt() - CNTVOFF_EL2); elsif HaveEL(EL2) && ELUsingAArch32(EL2) then X[t, 64] = CNTV_CVAL_EL0 - (PhysicalCountInt() - CNTVOFF); else X[t, 64] = CNTV_CVAL_EL0 - PhysicalCountInt();

#### MSR CNTV_TVAL_EL0, <Xt>

op0 | op1 | CRn | CRm | op2
--- | --- | --- | --- | ---
0b11 | 0b011 | 0b1110 | 0b0011 | 0b000

if PSTATE.EL == EL0 then if !ELIsInHost(EL0) && CNTKCTL_EL1.EL0VTEN == '0' then if EL2Enabled() && HCR_EL2.TGE == '1' then AArch64.SystemAccessTrap(EL2, 0x18); else AArch64.SystemAccessTrap(EL1, 0x18); elsif ELIsInHost(EL0) && CNTHCTL_EL2.EL0VTEN == '0' then AArch64.SystemAccessTrap(EL2, 0x18); elsif EL2Enabled() && !ELIsInHost(EL0) && IsFeatureImplemented(FEAT_ECV) && CNTHCTL_EL2.EL1TVT == '1' then AArch64.SystemAccessTrap(EL2, 0x18); elsif ELIsInHost(EL0) && IsCurrentSecurityState(SS_Secure) && IsFeatureImplemented(FEAT_SEL2) then CNTHVS_CVAL_EL2 = SignExtend(X[t, 64]<31:0>, 64) + PhysicalCountInt(); elsif ELIsInHost(EL0) && !IsCurrentSecurityState(SS_Secure) then CNTHV_CVAL_EL2 = SignExtend(X[t, 64]<31:0>, 64) + PhysicalCountInt(); elsif HaveEL(EL2) && (!EL2Enabled() || !ELIsInHost(EL0)) then CNTV_CVAL_EL0 = (SignExtend(X[t, 64]<31:0>, 64) + PhysicalCountInt()) - CNTVOFF_EL2; else CNTV_CVAL_EL0 = SignExtend(X[t, 64]<31:0>, 64) + PhysicalCountInt(); elsif PSTATE.EL == EL1 then if EL2Enabled() && IsFeatureImplemented(FEAT_ECV) && CNTHCTL_EL2.EL1TVT == '1' then AArch64.SystemAccessTrap(EL2, 0x18); elsif HaveEL(EL2) then CNTV_CVAL_EL0 = (SignExtend(X[t, 64]<31:0>, 64) + PhysicalCountInt()) - CNTVOFF_EL2; else CNTV_CVAL_EL0 = SignExtend(X[t, 64]<31:0>, 64) + PhysicalCountInt(); elsif PSTATE.EL == EL2 then if ELIsInHost(EL2) && IsCurrentSecurityState(SS_Secure) && IsFeatureImplemented(FEAT_SEL2) then CNTHVS_CVAL_EL2 = SignExtend(X[t, 64]<31:0>, 64) + PhysicalCountInt(); elsif ELIsInHost(EL2) && !IsCurrentSecurityState(SS_Secure) then CNTHV_CVAL_EL2 = SignExtend(X[t, 64]<31:0>, 64) + PhysicalCountInt(); elsif !ELIsInHost(EL2) then CNTV_CVAL_EL0 = (SignExtend(X[t, 64]<31:0>, 64) + PhysicalCountInt()) - CNTVOFF_EL2; else CNTV_CVAL_EL0 = SignExtend(X[t, 64]<31:0>, 64) + PhysicalCountInt(); elsif PSTATE.EL == EL3 then if HaveEL(EL2) && !ELUsingAArch32(EL2) then CNTV_CVAL_EL0 = (SignExtend(X[t, 64]<31:0>, 64) + PhysicalCountInt()) - CNTVOFF_EL2; elsif HaveEL(EL2) && ELUsingAArch32(EL2) then CNTV_CVAL_EL0 = (SignExtend(X[t, 64]<31:0>, 64) + PhysicalCountInt()) - CNTVOFF; else CNTV_CVAL_EL0 = SignExtend(X[t, 64]<31:0>, 64) + PhysicalCountInt();

#### MRS <Xt>, CNTV_TVAL_EL02

op0 | op1 | CRn | CRm | op2
--- | --- | --- | --- | ---
0b11 | 0b101 | 0b1110 | 0b0011 | 0b000

if PSTATE.EL == EL0 then UNDEFINED; elsif PSTATE.EL == EL1 then if EffectiveHCR_EL2_NVx() IN {'xx1'} then AArch64.SystemAccessTrap(EL2, 0x18); else UNDEFINED; elsif PSTATE.EL == EL2 then if ELIsInHost(EL2) then if CNTV_CTL_EL0.ENABLE == '0' then X[t, 64] = bits(64) UNKNOWN; else X[t, 64] = CNTV_CVAL_EL0 - (PhysicalCountInt() - CNTVOFF_EL2); else UNDEFINED; elsif PSTATE.EL == EL3 then if ELIsInHost(EL2) then if CNTV_CTL_EL0.ENABLE == '0' then X[t, 64] = bits(64) UNKNOWN; else X[t, 64] = CNTV_CVAL_EL0 - (PhysicalCountInt() - CNTVOFF_EL2); else UNDEFINED;

#### MSR CNTV_TVAL_EL02, <Xt>

op0 | op1 | CRn | CRm | op2
--- | --- | --- | --- | ---
0b11 | 0b101 | 0b1110 | 0b0011 | 0b000

if PSTATE.EL == EL0 then UNDEFINED; elsif PSTATE.EL == EL1 then if EffectiveHCR_EL2_NVx() IN {'xx1'} then AArch64.SystemAccessTrap(EL2, 0x18); else UNDEFINED; elsif PSTATE.EL == EL2 then if ELIsInHost(EL2) then CNTV_CVAL_EL0 = (SignExtend(X[t, 64]<31:0>, 64) + PhysicalCountInt()) - CNTVOFF_EL2; else UNDEFINED; elsif PSTATE.EL == EL3 then if ELIsInHost(EL2) then CNTV_CVAL_EL0 = (SignExtend(X[t, 64]<31:0>, 64) + PhysicalCountInt()) - CNTVOFF_EL2; else UNDEFINED;

AArch32 Registers | AArch64 Registers | AArch32 Instructions | AArch64 Instructions | Index by Encoding | External Registers | External Registers by Offset | Registers by Functional Group | Proprietary Notice

26/03/2024 09:49; 67c0ae5282a7629ba0ea0ba7267b43cd4f7939f6

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