ZCR_EL3, SVE Control Register (EL3)

The ZCR_EL3 characteristics are:

Purpose

This register controls aspects of SVE visible at all Exception levels.

Configuration

This register is present only when FEAT_SVE is implemented. Otherwise, direct accesses to ZCR_EL3 are UNDEFINED.

Attributes

ZCR_EL3 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 all Exception levels to (LEN+1)*128 bits.

An implementation is permitted to include any set of vector lengths that are multiples of 128 bits, from 128 bits to 2048 bits inclusive, and required to support all vector lengths that are powers of two, from 128 bits up to its maximum implemented vector length.

For all purposes other than returning the result of a direct read of ZCR_EL3, this field selects the effective vector length as follows:

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.

The reset behavior of this field is:

Accessing ZCR_EL3

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

MRS <Xt>, ZCR_EL3

op0op1CRnCRmop2
0b110b1100b00010b00100b000

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>

op0op1CRnCRmop2
0b110b1100b00010b00100b000

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];


30/09/2021 15:34; 092b4e1bbfbb45a293b198f9330c5f529ead2b0f

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