ZCR_EL3, SVE Control Register for EL3
The ZCR_EL3 characteristics are:
Purpose
The SVE Control Register for EL3 is used to control aspects of SVE visible at all Exception levels.
Configuration
This register is present only when SVE is implemented. Otherwise, direct accesses to ZCR_EL3 are UNDEFINED.
RW fields in this register reset to architecturally UNKNOWN values.
Attributes
ZCR_EL3 is a 64-bit register.
Field descriptions
The ZCR_EL3 bit assignments are:
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 |
RES0 | |||||||||||||||||||||||||||||||
RES0 | RAZ/WI | LEN | |||||||||||||||||||||||||||||
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 |
Bits [63:9]
Reserved, RES0.
Bits [8:4]
Reserved, RAZ/WI.
LEN, bits [3:0]
Constrains the scalable vector register length for all Exception levels to (LEN+1)x128 bits. For all purposes other than returning the result of a direct read of ZCR_EL3 then this field behaves as if rounded down to the nearest implemented vector length.
An indirect read of ZCR_EL3.LEN appears to occur in program order relative to a direct write of the same register, without the need for explicit synchronization.
This field resets to an architecturally UNKNOWN value.
Accessing the ZCR_EL3
Accesses to this register use the following encodings:
MRS <Xt>, ZCR_EL3
op0 | op1 | CRn | CRm | op2 |
---|---|---|---|---|
0b11 | 0b110 | 0b0001 | 0b0010 | 0b000 |
if PSTATE.EL == EL0 then UNDEFINED; elsif PSTATE.EL == EL1 then UNDEFINED; elsif PSTATE.EL == EL2 then UNDEFINED; elsif PSTATE.EL == EL3 then if CPTR_EL3.EZ == '0' then AArch64.SystemAccessTrap(EL3, 0x19); else return ZCR_EL3;
MSR ZCR_EL3, <Xt>
op0 | op1 | CRn | CRm | op2 |
---|---|---|---|---|
0b11 | 0b110 | 0b0001 | 0b0010 | 0b000 |
if PSTATE.EL == EL0 then UNDEFINED; elsif PSTATE.EL == EL1 then UNDEFINED; elsif PSTATE.EL == EL2 then UNDEFINED; elsif PSTATE.EL == EL3 then if CPTR_EL3.EZ == '0' then AArch64.SystemAccessTrap(EL3, 0x19); else ZCR_EL3 = X[t];