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ICH_HCR, Interrupt Controller Hyp Control Register

The ICH_HCR characteristics are:

Purpose

Controls the environment for VMs.

Configuration

AArch32 System register ICH_HCR bits [31:0] are architecturally mapped to AArch64 System register ICH_HCR_EL2[31:0] .

This register is present only when AArch32 is supported at any Exception level. Otherwise, direct accesses to ICH_HCR are UNDEFINED.

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

Attributes

ICH_HCR is a 32-bit register.

Field descriptions

The ICH_HCR bit assignments are:

EOIcount, bits [31:27]

This field is incremented whenever a successful write to a virtual EOIR or DIR register would have resulted in a virtual interrupt deactivation. That is either:

  • A virtual write to EOIR with a valid interrupt identifier that is not in the LPI range (that is < 8192) when EOI mode is zero and no List Register was found.
  • A virtual write to DIR with a valid interrupt identifier that is not in the LPI range (that is < 8192) when EOI mode is one and no List Register was found.

This allows software to manage more active interrupts than there are implemented List Registers.

It is CONSTRAINED UNPREDICTABLE whether a virtual write to EOIR that does not clear a bit in the Active Priorities registers (ICH_AP0R<n>/ICH_AP1R<n>) increments EOIcount. Permitted behaviors are:

  • Increment EOIcount.
  • Leave EOIcount unchanged.

This field resets to 0.

Bits [26:15]

Reserved, RES0.

TDIR, bit [14]

Trap Non-secure EL1 writes to ICC_DIR and ICV_DIR.

TDIRMeaning
0b0

Non-secure EL1 writes of ICC_DIR and ICV_DIR are not trapped to EL2, unless trapped by other mechanisms.

0b1

Non-secure EL1 writes of ICV_DIR are trapped to EL2. It is IMPLEMENTATION DEFINED whether Non-secure writes of ICC_DIR are trapped. Not trapping ICC_DIR writes is DEPRECATED.

Support for this bit is OPTIONAL, with support indicated by ICH_VTR.

If the implementation does not support this trap, this bit is RES0.

Arm deprecates not including this trap bit.

This field resets to 0.

TSEI, bit [13]

Trap all locally generated SEIs. This bit allows the hypervisor to intercept locally generated SEIs that would otherwise be taken at Non-secure EL1.

TSEIMeaning
0b0

Locally generated SEIs do not cause a trap to EL2.

0b1

Locally generated SEIs trap to EL2.

If ICH_VTR.SEIS is 0, this bit is RES0.

This field resets to 0.

TALL1, bit [12]

Trap all Non-secure EL1 accesses to ICC_* and ICV_* System registers for Group 1 interrupts to EL2.

TALL1Meaning
0b0

Non-secure EL1 accesses to ICC_* and ICV_* registers for Group 1 interrupts proceed as normal.

0b1

Non-secure EL1 accesses to ICC_* and ICV_* registers for Group 1 interrupts trap to EL2.

This field resets to 0.

TALL0, bit [11]

Trap all Non-secure EL1 accesses to ICC_* and ICV_* System registers for Group 0 interrupts to EL2.

TALL0Meaning
0b0

Non-secure EL1 accesses to ICC_* and ICV_* registers for Group 0 interrupts proceed as normal.

0b1

Non-secure EL1 accesses to ICC_* and ICV_* registers for Group 0 interrupts trap to EL2.

This field resets to 0.

TC, bit [10]

Trap all Non-secure EL1 accesses to System registers that are common to Group 0 and Group 1 to EL2.

TCMeaning
0b0

Non-secure EL1 accesses to common registers proceed as normal.

0b1

Non-secure EL1 accesses to common registers trap to EL2.

This affects accesses to ICC_SGI0R, ICC_SGI1R, ICC_ASGI1R, ICC_CTLR, ICC_DIR, ICC_PMR, ICC_RPR, ICV_CTLR, ICV_DIR, ICV_PMR, and ICV_RPR.

This field resets to 0.

Bit [9]

Reserved, RES0.

vSGIEOICount, bit [8]

When FEAT_GICv4p1 is implemented:

Controls whether deactivation of virtual SGIs can increment ICH_HCR_EL2.EOIcount

vSGIEOICountMeaning
0b0

Deactivation of virtual SGIs can increment ICH_HCR.EOIcount.

0b1

Deactivation of virtual SGIs does not increment ICH_HCR.EOIcount.

This field resets to 0.


Otherwise:

Reserved, RES0.

VGrp1DIE, bit [7]

VM Group 1 Disabled Interrupt Enable. Enables the signaling of a maintenance interrupt while signaling of Group 1 interrupts from the virtual CPU interface to the connected vPE is disabled:

VGrp1DIEMeaning
0b0

Maintenance interrupt disabled.

0b1

Maintenance interrupt signaled when ICH_VMCR.VENG1 is 0.

This field resets to 0.

VGrp1EIE, bit [6]

VM Group 1 Enabled Interrupt Enable. Enables the signaling of a maintenance interrupt while signaling of Group 1 interrupts from the virtual CPU interface to the connected vPE is enabled:

VGrp1EIEMeaning
0b0

Maintenance interrupt disabled.

0b1

Maintenance interrupt signaled when ICH_VMCR.VENG1 is 1.

This field resets to 0.

VGrp0DIE, bit [5]

VM Group 0 Disabled Interrupt Enable. Enables the signaling of a maintenance interrupt while signaling of Group 0 interrupts from the virtual CPU interface to the connected vPE is disabled:

VGrp0DIEMeaning
0b0

Maintenance interrupt disabled.

0b1

Maintenance interrupt signaled when ICH_VMCR.VENG0 is 0.

This field resets to 0.

VGrp0EIE, bit [4]

VM Group 0 Enabled Interrupt Enable. Enables the signaling of a maintenance interrupt while signaling of Group 0 interrupts from the virtual CPU interface to the connected vPE is enabled:

VGrp0EIEMeaning
0b0

Maintenance interrupt disabled.

0b1

Maintenance interrupt signaled when ICH_VMCR.VENG0 is 1.

This field resets to 0.

NPIE, bit [3]

No Pending Interrupt Enable. Enables the signaling of a maintenance interrupt when there are no List registers with the State field set to 0b01 (pending):

NPIEMeaning
0b0

Maintenance interrupt disabled.

0b1

Maintenance interrupt signaled while the List registers contain no interrupts in the pending state.

This field resets to 0.

LRENPIE, bit [2]

List Register Entry Not Present Interrupt Enable. Enables the signaling of a maintenance interrupt while the virtual CPU interface does not have a corresponding valid List register entry for an EOI request:

LRENPIEMeaning
0b0

Maintenance interrupt disabled.

0b1

Maintenance interrupt is asserted while the EOIcount field is not 0.

This field resets to 0.

UIE, bit [1]

Underflow Interrupt Enable. Enables the signaling of a maintenance interrupt when the List registers are empty, or hold only one valid entry:

UIEMeaning
0b0

Maintenance interrupt disabled.

0b1

Maintenance interrupt is asserted if none, or only one, of the List register entries is marked as a valid interrupt.

This field resets to 0.

En, bit [0]

Enable. Global enable bit for the virtual CPU interface:

EnMeaning
0b0

Virtual CPU interface operation disabled.

0b1

Virtual CPU interface operation enabled.

When this field is set to 0:

  • The virtual CPU interface does not signal any maintenance interrupts.
  • The virtual CPU interface does not signal any virtual interrupts.
  • A read of ICV_IAR0, ICV_IAR1, GICV_IAR or GICV_AIAR returns a spurious interrupt ID.

This field resets to 0.

Accessing the ICH_HCR

Accesses to this register use the following encodings:

MRC{<c>}{<q>} <coproc>, {#}<opc1>, <Rt>, <CRn>, <CRm>{, {#}<opc2>}

coprocopc1CRnCRmopc2
0b11110b1000b11000b10110b000
if PSTATE.EL == EL0 then
    UNDEFINED;
elsif PSTATE.EL == EL1 then
    if EL2Enabled() && !ELUsingAArch32(EL2) && HSTR_EL2.T12 == '1' then
        AArch64.AArch32SystemAccessTrap(EL2, 0x03);
    elsif EL2Enabled() && ELUsingAArch32(EL2) && HSTR.T12 == '1' then
        AArch32.TakeHypTrapException(0x03);
    else
        UNDEFINED;
elsif PSTATE.EL == EL2 then
    if ICC_HSRE.SRE == '0' then
        UNDEFINED;
    else
        return ICH_HCR;
elsif PSTATE.EL == EL3 then
    if ICC_MSRE.SRE == '0' then
        UNDEFINED;
    else
        return ICH_HCR;
              

MCR{<c>}{<q>} <coproc>, {#}<opc1>, <Rt>, <CRn>, <CRm>{, {#}<opc2>}

coprocopc1CRnCRmopc2
0b11110b1000b11000b10110b000
if PSTATE.EL == EL0 then
    UNDEFINED;
elsif PSTATE.EL == EL1 then
    if EL2Enabled() && !ELUsingAArch32(EL2) && HSTR_EL2.T12 == '1' then
        AArch64.AArch32SystemAccessTrap(EL2, 0x03);
    elsif EL2Enabled() && ELUsingAArch32(EL2) && HSTR.T12 == '1' then
        AArch32.TakeHypTrapException(0x03);
    else
        UNDEFINED;
elsif PSTATE.EL == EL2 then
    if ICC_HSRE.SRE == '0' then
        UNDEFINED;
    else
        ICH_HCR = R[t];
elsif PSTATE.EL == EL3 then
    if ICC_MSRE.SRE == '0' then
        UNDEFINED;
    else
        ICH_HCR = R[t];