VBAR_EL1

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VBAR_EL1, Vector Base Address Register (EL1)

Purpose

Configuration

AArch64 System register VBAR_EL1 bits [31:0] are architecturally mapped to AArch32 System register VBAR[31:0].

This register is present only when FEAT_AA64 is implemented. Otherwise, direct accesses to VBAR_EL1 are UNDEFINED.

Attributes

Field descriptions

VBA, bits [63:11]

Vector Base Address. Base address of the exception vectors for exceptions taken to EL1.

Note

If the implementation supports FEAT_LVA3, then:

If tagged addresses are not being used, bits [63:56] of VBAR_EL1 must be the same or else the use of the vector address will result in a recursive exception.

Otherwise:

If the implementation supports FEAT_LVA, then:

If tagged addresses are being used, bits [55:52] of VBAR_EL1 must be the same or else the use of the vector address will result in a recursive exception.
If tagged addresses are not being used, bits [63:52] of VBAR_EL1 must be the same or else the use of the vector address will result in a recursive exception.

If the implementation does not support FEAT_LVA, then:

If tagged addresses are being used, bits [55:48] of VBAR_EL1 must be the same or else the use of the vector address will result in a recursive exception.
If tagged addresses are not being used, bits [63:48] of VBAR_EL1 must be the same or else the use of the vector address will result in a recursive exception.

The reset behavior of this field is:

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

Bits [10:0]

Accessing VBAR_EL1

When the Effective value of HCR_EL2.E2H is 1, without explicit synchronization, accesses from EL3 using the accessor name VBAR_EL1 or VBAR_EL12 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>, VBAR_EL1

op0	op1	CRn	CRm	op2
0b11	0b000	0b1100	0b0000	0b000

if !IsFeatureImplemented(FEAT_AA64) then Undefined(); elsif PSTATE.EL == EL0 then Undefined(); elsif PSTATE.EL == EL1 then if EffectiveHCR_EL2_NVx() == '011' then AArch64_SystemAccessTrap(EL2, 0x18); elsif EL2Enabled() && IsFeatureImplemented(FEAT_FGT) && (!HaveEL(EL3) || SCR_EL3().FGTEn == '1') && HFGRTR_EL2().VBAR_EL1 == '1' then AArch64_SystemAccessTrap(EL2, 0x18); elsif EffectiveHCR_EL2_NVx() IN {'111'} then X{64}(t) = NVMem(0x250); else X{64}(t) = VBAR_EL1(); end; elsif PSTATE.EL == EL2 then if ELIsInHost(EL2) then X{64}(t) = VBAR_EL2(); else X{64}(t) = VBAR_EL1(); end; elsif PSTATE.EL == EL3 then X{64}(t) = VBAR_EL1(); end;

MSR VBAR_EL1, <Xt>

op0	op1	CRn	CRm	op2
0b11	0b000	0b1100	0b0000	0b000

if !IsFeatureImplemented(FEAT_AA64) then Undefined(); elsif PSTATE.EL == EL0 then Undefined(); elsif PSTATE.EL == EL1 then if EffectiveHCR_EL2_NVx() == '011' then AArch64_SystemAccessTrap(EL2, 0x18); elsif EL2Enabled() && IsFeatureImplemented(FEAT_FGT) && (!HaveEL(EL3) || SCR_EL3().FGTEn == '1') && HFGWTR_EL2().VBAR_EL1 == '1' then AArch64_SystemAccessTrap(EL2, 0x18); elsif EffectiveHCR_EL2_NVx() IN {'111'} then NVMem(0x250) = X{64}(t); else VBAR_EL1() = X{64}(t); end; elsif PSTATE.EL == EL2 then if ELIsInHost(EL2) then VBAR_EL2() = X{64}(t); else VBAR_EL1() = X{64}(t); end; elsif PSTATE.EL == EL3 then VBAR_EL1() = X{64}(t); end;

When FEAT_VHE is implemented

MRS <Xt>, VBAR_EL12

op0	op1	CRn	CRm	op2
0b11	0b101	0b1100	0b0000	0b000

if !IsFeatureImplemented(FEAT_AA64) then Undefined(); elsif PSTATE.EL == EL0 then Undefined(); elsif PSTATE.EL == EL1 then if EffectiveHCR_EL2_NVx() == '101' then X{64}(t) = NVMem(0x250); elsif EffectiveHCR_EL2_NVx() IN {'xx1'} then AArch64_SystemAccessTrap(EL2, 0x18); else Undefined(); end; elsif PSTATE.EL == EL2 then if ELIsInHost(EL2) then X{64}(t) = VBAR_EL1(); else Undefined(); end; elsif PSTATE.EL == EL3 then if ELIsInHost(EL2) then X{64}(t) = VBAR_EL1(); else Undefined(); end; end;

When FEAT_VHE is implemented

MSR VBAR_EL12, <Xt>

op0	op1	CRn	CRm	op2
0b11	0b101	0b1100	0b0000	0b000

if !IsFeatureImplemented(FEAT_AA64) then Undefined(); elsif PSTATE.EL == EL0 then Undefined(); elsif PSTATE.EL == EL1 then if EffectiveHCR_EL2_NVx() == '101' then NVMem(0x250) = X{64}(t); elsif EffectiveHCR_EL2_NVx() IN {'xx1'} then AArch64_SystemAccessTrap(EL2, 0x18); else Undefined(); end; elsif PSTATE.EL == EL2 then if ELIsInHost(EL2) then VBAR_EL1() = X{64}(t); else Undefined(); end; elsif PSTATE.EL == EL3 then if ELIsInHost(EL2) then VBAR_EL1() = X{64}(t); else Undefined(); end; end;

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VBA
VBA																					RES0