ACTLR_EL2, Auxiliary Control Register (EL2)
The ACTLR_EL2 characteristics are:
Purpose
Provides IMPLEMENTATION DEFINED configuration and control options for EL2.
Arm recommends the contents of this register are updated to apply to EL0 when HCR_EL2.{E2H, TGE} is {1, 1}, gaining configuration and control fields from the ACTLR_EL1. This avoids the need for software to manage the contents of these register when switching between a Guest OS and a Host OS.
Configuration
AArch64 System register ACTLR_EL2 bits [31:0] are architecturally mapped to AArch32 System register HACTLR[31:0] .
AArch64 System register ACTLR_EL2 bits [63:32] are architecturally mapped to AArch32 System register HACTLR2[31:0] .
If EL2 is not implemented, this register is RES0 from EL3.
This register has no effect if EL2 is not enabled in the current Security state.
RW fields in this register reset to architecturally UNKNOWN values.
Attributes
ACTLR_EL2 is a 64-bit register.
Field descriptions
The ACTLR_EL2 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 |
| IMPLEMENTATION DEFINED | |||||||||||||||||||||||||||||||
| IMPLEMENTATION DEFINED | |||||||||||||||||||||||||||||||
| 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 |
IMPLEMENTATION DEFINED, bits [63:0]
IMPLEMENTATION DEFINED.
This field resets to an architecturally UNKNOWN value.
Accessing the ACTLR_EL2
Accesses to this register use the following encodings:
MRS <Xt>, ACTLR_EL2
| op0 | op1 | CRn | CRm | op2 |
|---|---|---|---|---|
| 0b11 | 0b100 | 0b0001 | 0b0000 | 0b001 |
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
return ACTLR_EL2;
elsif PSTATE.EL == EL3 then
return ACTLR_EL2;
MSR ACTLR_EL2, <Xt>
| op0 | op1 | CRn | CRm | op2 |
|---|---|---|---|---|
| 0b11 | 0b100 | 0b0001 | 0b0000 | 0b001 |
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
ACTLR_EL2 = X[t];
elsif PSTATE.EL == EL3 then
ACTLR_EL2 = X[t];