ZCR_EL2, SVE Control Register (EL2)

The ZCR_EL2 characteristics are:

Purpose

This register controls aspects of SVE visible at Exception levels EL2, EL1, and EL0.

Configuration

This register is present only when FEAT_SVE is implemented. Otherwise, direct accesses to ZCR_EL2 are UNDEFINED.

This register has no effect if EL2 is not enabled in the current Security state, or if the PE is in Streaming SVE mode.

Attributes

ZCR_EL2 is a 64-bit register.

Field descriptions

6362616059585756555453525150494847464544434241403938373635343332
313029282726252423222120191817161514131211109876543210
RES0
RES0RAZ/WILEN

Bits [63:9]

Reserved, RES0.

Bits [8:4]

Reserved, RAZ/WI.

LEN, bits [3:0]

Effective SVE Vector Length (VL).

Constrains the effective scalable vector register length for EL2, EL1, and EL0 to (LEN+1)*128 bits when EL2 is enabled in the current Security state and when the PE is not in Streaming SVE mode.

For all purposes other than returning the result of a direct read of ZCR_EL2, this field selects the effective vector length as follows:

An indirect read of ZCR_EL2.LEN appears to occur in program order relative to a direct write of the same register, without the need for explicit synchronization.

The reset behaviour of this field is:

Accessing ZCR_EL2

When HCR_EL2.E2H is 1, without explicit synchronization, access from EL2 using the mnemonic ZCR_EL2 or ZCR_EL1 are not guaranteed to be ordered with respect to accesses using the other mnemonic.

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

MRS <Xt>, ZCR_EL2

op0op1CRnCRmop2
0b110b1000b00010b00100b000

if PSTATE.EL == EL0 then UNDEFINED; elsif PSTATE.EL == EL1 then if EL2Enabled() && HCR_EL2.NV == '1' then AArch64.SystemAccessTrap(EL2, 0x18); else UNDEFINED; elsif PSTATE.EL == EL2 then if Halted() && HaveEL(EL3) && EDSCR.SDD == '1' && boolean IMPLEMENTATION_DEFINED "EL3 trap priority when SDD == '1'" && CPTR_EL3.EZ == '0' then UNDEFINED; elsif HCR_EL2.E2H == '0' && CPTR_EL2.TZ == '1' then AArch64.SystemAccessTrap(EL2, 0x19); elsif HCR_EL2.E2H == '1' && CPTR_EL2.ZEN == 'x0' then AArch64.SystemAccessTrap(EL2, 0x19); elsif HaveEL(EL3) && CPTR_EL3.EZ == '0' then if Halted() && EDSCR.SDD == '1' then UNDEFINED; else AArch64.SystemAccessTrap(EL3, 0x19); else return ZCR_EL2; elsif PSTATE.EL == EL3 then if CPTR_EL3.EZ == '0' then AArch64.SystemAccessTrap(EL3, 0x19); else return ZCR_EL2;

MSR ZCR_EL2, <Xt>

op0op1CRnCRmop2
0b110b1000b00010b00100b000

if PSTATE.EL == EL0 then UNDEFINED; elsif PSTATE.EL == EL1 then if EL2Enabled() && HCR_EL2.NV == '1' then AArch64.SystemAccessTrap(EL2, 0x18); else UNDEFINED; elsif PSTATE.EL == EL2 then if Halted() && HaveEL(EL3) && EDSCR.SDD == '1' && boolean IMPLEMENTATION_DEFINED "EL3 trap priority when SDD == '1'" && CPTR_EL3.EZ == '0' then UNDEFINED; elsif HCR_EL2.E2H == '0' && CPTR_EL2.TZ == '1' then AArch64.SystemAccessTrap(EL2, 0x19); elsif HCR_EL2.E2H == '1' && CPTR_EL2.ZEN == 'x0' then AArch64.SystemAccessTrap(EL2, 0x19); elsif HaveEL(EL3) && CPTR_EL3.EZ == '0' then if Halted() && EDSCR.SDD == '1' then UNDEFINED; else AArch64.SystemAccessTrap(EL3, 0x19); else ZCR_EL2 = X[t]; elsif PSTATE.EL == EL3 then if CPTR_EL3.EZ == '0' then AArch64.SystemAccessTrap(EL3, 0x19); else ZCR_EL2 = X[t];

MRS <Xt>, ZCR_EL1

op0op1CRnCRmop2
0b110b0000b00010b00100b000

if PSTATE.EL == EL0 then UNDEFINED; elsif PSTATE.EL == EL1 then if Halted() && HaveEL(EL3) && EDSCR.SDD == '1' && boolean IMPLEMENTATION_DEFINED "EL3 trap priority when SDD == '1'" && CPTR_EL3.EZ == '0' then UNDEFINED; elsif CPACR_EL1.ZEN == 'x0' then AArch64.SystemAccessTrap(EL1, 0x19); elsif EL2Enabled() && HCR_EL2.E2H == '0' && CPTR_EL2.TZ == '1' then AArch64.SystemAccessTrap(EL2, 0x19); elsif EL2Enabled() && HCR_EL2.E2H == '1' && CPTR_EL2.ZEN == 'x0' then AArch64.SystemAccessTrap(EL2, 0x19); elsif HaveEL(EL3) && CPTR_EL3.EZ == '0' then if Halted() && EDSCR.SDD == '1' then UNDEFINED; else AArch64.SystemAccessTrap(EL3, 0x19); elsif EL2Enabled() && HCR_EL2.<NV2,NV1,NV> == '111' then return NVMem[0x1E0]; else return ZCR_EL1; elsif PSTATE.EL == EL2 then if Halted() && HaveEL(EL3) && EDSCR.SDD == '1' && boolean IMPLEMENTATION_DEFINED "EL3 trap priority when SDD == '1'" && CPTR_EL3.EZ == '0' then UNDEFINED; elsif HCR_EL2.E2H == '0' && CPTR_EL2.TZ == '1' then AArch64.SystemAccessTrap(EL2, 0x19); elsif HCR_EL2.E2H == '1' && CPTR_EL2.ZEN == 'x0' then AArch64.SystemAccessTrap(EL2, 0x19); elsif HaveEL(EL3) && CPTR_EL3.EZ == '0' then if Halted() && EDSCR.SDD == '1' then UNDEFINED; else AArch64.SystemAccessTrap(EL3, 0x19); elsif HCR_EL2.E2H == '1' then return ZCR_EL2; else return ZCR_EL1; elsif PSTATE.EL == EL3 then if CPTR_EL3.EZ == '0' then AArch64.SystemAccessTrap(EL3, 0x19); else return ZCR_EL1;

MSR ZCR_EL1, <Xt>

op0op1CRnCRmop2
0b110b0000b00010b00100b000

if PSTATE.EL == EL0 then UNDEFINED; elsif PSTATE.EL == EL1 then if Halted() && HaveEL(EL3) && EDSCR.SDD == '1' && boolean IMPLEMENTATION_DEFINED "EL3 trap priority when SDD == '1'" && CPTR_EL3.EZ == '0' then UNDEFINED; elsif CPACR_EL1.ZEN == 'x0' then AArch64.SystemAccessTrap(EL1, 0x19); elsif EL2Enabled() && HCR_EL2.E2H == '0' && CPTR_EL2.TZ == '1' then AArch64.SystemAccessTrap(EL2, 0x19); elsif EL2Enabled() && HCR_EL2.E2H == '1' && CPTR_EL2.ZEN == 'x0' then AArch64.SystemAccessTrap(EL2, 0x19); elsif HaveEL(EL3) && CPTR_EL3.EZ == '0' then if Halted() && EDSCR.SDD == '1' then UNDEFINED; else AArch64.SystemAccessTrap(EL3, 0x19); elsif EL2Enabled() && HCR_EL2.<NV2,NV1,NV> == '111' then NVMem[0x1E0] = X[t]; else ZCR_EL1 = X[t]; elsif PSTATE.EL == EL2 then if Halted() && HaveEL(EL3) && EDSCR.SDD == '1' && boolean IMPLEMENTATION_DEFINED "EL3 trap priority when SDD == '1'" && CPTR_EL3.EZ == '0' then UNDEFINED; elsif HCR_EL2.E2H == '0' && CPTR_EL2.TZ == '1' then AArch64.SystemAccessTrap(EL2, 0x19); elsif HCR_EL2.E2H == '1' && CPTR_EL2.ZEN == 'x0' then AArch64.SystemAccessTrap(EL2, 0x19); elsif HaveEL(EL3) && CPTR_EL3.EZ == '0' then if Halted() && EDSCR.SDD == '1' then UNDEFINED; else AArch64.SystemAccessTrap(EL3, 0x19); elsif HCR_EL2.E2H == '1' then ZCR_EL2 = X[t]; else ZCR_EL1 = X[t]; elsif PSTATE.EL == EL3 then if CPTR_EL3.EZ == '0' then AArch64.SystemAccessTrap(EL3, 0x19); else ZCR_EL1 = X[t];


30/06/2021 15:22; 2a17f7750cfd1ab239f20f6cf29877ba8041794f

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