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# CNTHVS_CTL_EL2, Counter-timer Secure Virtual Timer Control Register (EL2)

The CNTHVS_CTL_EL2 characteristics are:

## Purpose

Control register for the Secure EL2 virtual timer.

## Configuration

AArch64 System register CNTHVS_CTL_EL2 bits [31:0] are architecturally mapped to AArch32 System register CNTHVS_CTL[31:0].

This register is present only when FEAT_SEL2 is implemented and FEAT_VHE is implemented. Otherwise, direct accesses to CNTHVS_CTL_EL2 are UNDEFINED.

If EL2 is not implemented, this register is RES0 from EL3.

## Attributes

CNTHVS_CTL_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
RES0
RES0 | ISTATUS | IMASK | ENABLE

#### Bits [63:3]

Reserved, RES0.

#### ISTATUS, bit [2]

The status of the timer. This bit indicates whether the timer condition is met:

ISTATUS | Meaning
--- | ---
0b0 | Timer condition is not met.
0b1 | Timer condition is met.

When the value of the CNTHVS_CTL_EL2.ENABLE bit is 1, ISTATUS indicates whether the timer condition is met. ISTATUS takes no account of the value of the IMASK bit. If the value of ISTATUS is 1 and the value of IMASK is 0 then the timer interrupt is asserted.

When the value of the ENABLE bit is 0, the ISTATUS field is UNKNOWN.

The reset behavior of this field is:

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

Access to this field is RO.

#### IMASK, bit [1]

Timer interrupt mask bit. Permitted values are:

IMASK | Meaning
--- | ---
0b0 | Timer interrupt is not masked by the IMASK bit.
0b1 | Timer interrupt is masked by the IMASK bit.

For more information, see the description of the CNTHVS_CTL_EL2.ISTATUS bit.

The reset behavior of this field is:

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

#### ENABLE, bit [0]

Enables the timer. Permitted values are:

ENABLE | Meaning
--- | ---
0b0 | Timer disabled.
0b1 | Timer enabled.

Setting this bit to 0 disables the timer output signal, but the timer value accessible from CNTHVS_TVAL_EL2 continues to count down.

Note

Disabling the output signal might be a power-saving option.

The reset behavior of this field is:

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

## Accessing CNTHVS_CTL_EL2

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

#### MRS <Xt>, CNTHVS_CTL_EL2

op0 | op1 | CRn | CRm | op2
--- | --- | --- | --- | ---
0b11 | 0b100 | 0b1110 | 0b0100 | 0b001

if PSTATE.EL == EL0 then UNDEFINED; elsif PSTATE.EL == EL1 then if !IsCurrentSecurityState(SS_Secure) then UNDEFINED; elsif EffectiveHCR_EL2_NVx() IN {'xx1'} then AArch64.SystemAccessTrap(EL2, 0x18); else UNDEFINED; elsif PSTATE.EL == EL2 then if !IsCurrentSecurityState(SS_Secure) then UNDEFINED; else X[t, 64] = CNTHVS_CTL_EL2; elsif PSTATE.EL == EL3 then if SCR_EL3.EEL2 == '0' then UNDEFINED; else X[t, 64] = CNTHVS_CTL_EL2;

#### MSR CNTHVS_CTL_EL2, <Xt>

op0 | op1 | CRn | CRm | op2
--- | --- | --- | --- | ---
0b11 | 0b100 | 0b1110 | 0b0100 | 0b001

if PSTATE.EL == EL0 then UNDEFINED; elsif PSTATE.EL == EL1 then if !IsCurrentSecurityState(SS_Secure) then UNDEFINED; elsif EffectiveHCR_EL2_NVx() IN {'xx1'} then AArch64.SystemAccessTrap(EL2, 0x18); else UNDEFINED; elsif PSTATE.EL == EL2 then if !IsCurrentSecurityState(SS_Secure) then UNDEFINED; else CNTHVS_CTL_EL2 = X[t, 64]; elsif PSTATE.EL == EL3 then if SCR_EL3.EEL2 == '0' then UNDEFINED; else CNTHVS_CTL_EL2 = X[t, 64];

#### MRS <Xt>, CNTV_CTL_EL0

op0 | op1 | CRn | CRm | op2
--- | --- | --- | --- | ---
0b11 | 0b011 | 0b1110 | 0b0011 | 0b001

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 X[t, 64] = CNTHVS_CTL_EL2; elsif ELIsInHost(EL0) && !IsCurrentSecurityState(SS_Secure) then X[t, 64] = CNTHV_CTL_EL2; else X[t, 64] = CNTV_CTL_EL0; elsif PSTATE.EL == EL1 then if EL2Enabled() && IsFeatureImplemented(FEAT_ECV) && CNTHCTL_EL2.EL1TVT == '1' then AArch64.SystemAccessTrap(EL2, 0x18); elsif EffectiveHCR_EL2_NVx() IN {'111'} then X[t, 64] = NVMem[0x170]; else X[t, 64] = CNTV_CTL_EL0; elsif PSTATE.EL == EL2 then if ELIsInHost(EL2) && IsCurrentSecurityState(SS_Secure) && IsFeatureImplemented(FEAT_SEL2) then X[t, 64] = CNTHVS_CTL_EL2; elsif ELIsInHost(EL2) && !IsCurrentSecurityState(SS_Secure) then X[t, 64] = CNTHV_CTL_EL2; else X[t, 64] = CNTV_CTL_EL0; elsif PSTATE.EL == EL3 then X[t, 64] = CNTV_CTL_EL0;

#### MSR CNTV_CTL_EL0, <Xt>

op0 | op1 | CRn | CRm | op2
--- | --- | --- | --- | ---
0b11 | 0b011 | 0b1110 | 0b0011 | 0b001

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_CTL_EL2 = X[t, 64]; elsif ELIsInHost(EL0) && !IsCurrentSecurityState(SS_Secure) then CNTHV_CTL_EL2 = X[t, 64]; else CNTV_CTL_EL0 = X[t, 64]; elsif PSTATE.EL == EL1 then if EL2Enabled() && IsFeatureImplemented(FEAT_ECV) && CNTHCTL_EL2.EL1TVT == '1' then AArch64.SystemAccessTrap(EL2, 0x18); elsif EffectiveHCR_EL2_NVx() IN {'111'} then NVMem[0x170] = X[t, 64]; else CNTV_CTL_EL0 = X[t, 64]; elsif PSTATE.EL == EL2 then if ELIsInHost(EL2) && IsCurrentSecurityState(SS_Secure) && IsFeatureImplemented(FEAT_SEL2) then CNTHVS_CTL_EL2 = X[t, 64]; elsif ELIsInHost(EL2) && !IsCurrentSecurityState(SS_Secure) then CNTHV_CTL_EL2 = X[t, 64]; else CNTV_CTL_EL0 = X[t, 64]; elsif PSTATE.EL == EL3 then CNTV_CTL_EL0 = X[t, 64];

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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