DC CGSW, Data, Allocation Tag or unified Cache line Clean of Allocation Tags by Set/Way
The DC CGSW characteristics are:
Purpose
Clean Allocation Tags in data cache by set/way.
Configuration
This instruction is present only when ARMv8.5-MemTag is implemented. Otherwise, direct accesses to DC CGSW are UNDEFINED.
Attributes
DC CGSW is a 64-bit System instruction.
Field descriptions
The DC CGSW input value 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 | |||||||||||||||||||||||||||||||
| SetWay | Level | RES0 | |||||||||||||||||||||||||||||
| 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 [63:32]
Reserved, RES0.
SetWay, bits [31:4]
Contains two fields:
- Way, bits[31:32-A], the number of the way to operate on.
- Set, bits[B-1:L], the number of the set to operate on.
Bits[L-1:4] are RES0.
A = Log2(ASSOCIATIVITY), L = Log2(LINELEN), B = (L + S), S = Log2(NSETS).
ASSOCIATIVITY, LINELEN (line length, in bytes), and NSETS (number of sets) have their usual meanings and are the values for the cache level being operated on. The values of A and S are rounded up to the next integer.
Level, bits [3:1]
Cache level to operate on, minus 1. For example, this field is 0 for operations on L1 cache, or 1 for operations on L2 cache.
Bit [0]
Reserved, RES0.
Executing the DC CGSW instruction
If this instruction is executed with a set, way or level argument that is larger than the value supported by the implementation then the behavior is CONSTRAINED UNPREDICTABLE and one of the following occurs:
- The instruction is UNDEFINED.
- The instruction performs cache maintenance on one of:
- No cache lines.
- A single arbitrary cache line.
- Multiple arbitrary cache lines.
Accesses to this instruction use the following encodings:
DC CGSW, <Xt>
| op0 | op1 | CRn | CRm | op2 |
|---|---|---|---|---|
| 0b01 | 0b000 | 0b0111 | 0b1010 | 0b100 |
if PSTATE.EL == EL0 then
UNDEFINED;
elsif PSTATE.EL == EL1 then
if EL2Enabled() && !ELUsingAArch32(EL2) && HCR_EL2.TSW == '1' then
AArch64.SystemAccessTrap(EL2, 0x18);
else
DC_CISW(X[t]);
elsif PSTATE.EL == EL2 then
DC_CISW(X[t]);
elsif PSTATE.EL == EL3 then
DC_CISW(X[t]);