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RMR_EL2, Reset Management Register (EL2)

The RMR_EL2 characteristics are:

Purpose

When this register is implemented:

  • A write to the register at EL2 can request a Warm reset.
  • If EL2 can use all Execution states, this register specifies the Execution state that the PE boots into on a Warm reset.

Configuration

AArch64 System register RMR_EL2 bits [31:0] are architecturally mapped to AArch32 System register HRMR[31:0] when the highest implemented Exception level is EL2.

This register is present only when the highest implemented Exception level is EL2. Otherwise, direct accesses to RMR_EL2 are UNDEFINED.

When EL2 is the highest implemented Exception level:

  • If EL2 can use all Execution states then this register must be implemented.
  • If EL2 cannot use AArch32 then it is IMPLEMENTATION DEFINED whether the register is implemented.

Attributes

RMR_EL2 is a 64-bit register.

Field descriptions

The RMR_EL2 bit assignments are:

6362616059585756555453525150494847464544434241403938373635343332
RES0
RES0RRAA64
313029282726252423222120191817161514131211109876543210

Bits [63:2]

Reserved, RES0.

RR, bit [1]

Reset Request. Setting this bit to 1 requests a Warm reset.

This field resets to 0.

AA64, bit [0]

When AArch32 is supported at any Exception level:

When EL2 can use AArch32, determines which Execution state the PE boots into after a Warm reset:

AA64Meaning
0b0

AArch32.

0b1

AArch64.

On coming out of the Warm reset, execution starts at the IMPLEMENTATION DEFINED reset vector address of the specified Execution state.

If EL2 can only use AArch64 state, this bit is RAO/WI.

When implemented as a RW field, this field resets to 1 on a Cold reset.


Otherwise:

Reserved, RAO/WI.

Accessing the RMR_EL2

Accesses to this register use the following encodings:

MRS <Xt>, RMR_EL2

op0op1CRnCRmop2
0b110b1000b11000b00000b010
if PSTATE.EL == EL1 && EL2Enabled() && IsHighestEL(EL2) && HCR_EL2.NV == '1' then
    AArch64.SystemAccessTrap(EL2, 0x18);
elsif PSTATE.EL == EL2 && IsHighestEL(EL2) then
    return RMR_EL2;
else
    UNDEFINED;
              

MSR RMR_EL2, <Xt>

op0op1CRnCRmop2
0b110b1000b11000b00000b010
if PSTATE.EL == EL1 && EL2Enabled() && IsHighestEL(EL2) && HCR_EL2.NV == '1' then
    AArch64.SystemAccessTrap(EL2, 0x18);
elsif PSTATE.EL == EL2 && IsHighestEL(EL2) then
    RMR_EL2 = X[t];
else
    UNDEFINED;