CurrentEL, Current Exception Level
The CurrentEL characteristics are:
Purpose
Holds the current Exception level.
Configuration
Some or all RW fields of this register have defined reset values. These apply only if the PE resets into an Exception level that is using AArch64. Otherwise, RW fields in this register reset to architecturally UNKNOWN values.
Attributes
CurrentEL is a 64-bit register.
Field descriptions
The CurrentEL 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 | EL | 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 [63:4]
Reserved, RES0.
EL, bits [3:2]
Current Exception level. Possible values of this field are:
| EL | Meaning |
|---|---|
| 0b00 |
EL0 |
| 0b01 |
EL1 |
| 0b10 |
EL2 |
| 0b11 |
EL3 |
When the HCR_EL2.NV bit is 1, EL1 read accesses to the CurrentEL register return the value of 0b10 in this field.
This field resets to the highest implemented Exception Level.
Bits [1:0]
Reserved, RES0.
Accessing the CurrentEL
Accesses to this register use the following encodings:
MRS <Xt>, CurrentEL
| op0 | op1 | CRn | CRm | op2 |
|---|---|---|---|---|
| 0b11 | 0b000 | 0b0100 | 0b0010 | 0b010 |
if PSTATE.EL == EL0 then
UNDEFINED;
elsif PSTATE.EL == EL1 then
if EL2Enabled() && HCR_EL2.NV == '1' then
return Zeros(60):'10':Zeros(2);
else
return Zeros(60):PSTATE.EL:Zeros(2);
elsif PSTATE.EL == EL2 then
return Zeros(60):PSTATE.EL:Zeros(2);
elsif PSTATE.EL == EL3 then
return Zeros(60):PSTATE.EL:Zeros(2);