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LORSA_EL1, LORegion Start Address (EL1)

The LORSA_EL1 characteristics are:

Purpose

Indicates whether the current LORegion descriptor selected by LORC_EL1.DS is enabled, and holds the physical address of the start of the LORegion.

Configuration

This register is present only when FEAT_LOR is implemented. Otherwise, direct accesses to LORSA_EL1 are UNDEFINED.

This register is RES0 if any of the following apply:

  • No LORegion descriptors are supported by the PE.
  • LORC_EL1.DS points to a LORegion that is not supported by the PE.

Attributes

LORSA_EL1 is a 64-bit register.

Field descriptions

The LORSA_EL1 bit assignments are:

6362616059585756555453525150494847464544434241403938373635343332
RES0SA[51:48]SA[47:16]
SA[47:16]RES0Valid
313029282726252423222120191817161514131211109876543210

Any of the fields in this register are permitted to be cached in a TLB.

Bits [63:52]

Reserved, RES0.

SA[51:48], bits [51:48]

When FEAT_LPA is implemented:

Extension to SA[47:16]. See SA[47:16] for more details.

This field resets to an architecturally UNKNOWN value.


Otherwise:

Reserved, RES0.

SA[47:16], bits [47:16]

Bits [47:16] of the start physical address of the LORegion described in the current LORegion descriptor selected by LORC_EL1.DS. Bits[15:0] of this address are defined to be 0x0000. For implementations with fewer than 48 bits, the upper bits of this field are RES0.

When FEAT_LPA is implemented, and 52-bit addresses and a 64KB translation granule are in use, SA[51:48] form the upper part of the address value. Otherwise, for implementations with fewer than 52 physical address bits, SA[51:48] are RES0.

This field resets to an architecturally UNKNOWN value.

Bits [15:1]

Reserved, RES0.

Valid, bit [0]

Indicates whether the current LORegion Descriptor is enabled.

ValidMeaning
0b0

Disabled

0b1

Enabled

This field resets to 0.

Accessing the LORSA_EL1

Accesses to this register use the following encodings:

MRS <Xt>, LORSA_EL1

op0op1CRnCRmop2
0b110b0000b10100b01000b000
if PSTATE.EL == EL0 then
    UNDEFINED;
elsif PSTATE.EL == EL1 then
    if Halted() && HaveEL(EL3) && EDSCR.SDD == '1' && boolean IMPLEMENTATION_DEFINED "EL3 trap priority when SDD == '1'" && SCR_EL3.TLOR == '1' then
        UNDEFINED;
    elsif SCR_EL3.NS == '0' then
        UNDEFINED;
    elsif EL2Enabled() && HCR_EL2.TLOR == '1' then
        AArch64.SystemAccessTrap(EL2, 0x18);
    elsif EL2Enabled() && (!HaveEL(EL3) || SCR_EL3.FGTEn == '1') && HFGRTR_EL2.LORSA_EL1 == '1' then
        AArch64.SystemAccessTrap(EL2, 0x18);
    elsif HaveEL(EL3) && SCR_EL3.TLOR == '1' then
        if Halted() && EDSCR.SDD == '1' then
            UNDEFINED;
        else
            AArch64.SystemAccessTrap(EL3, 0x18);
    else
        return LORSA_EL1;
elsif PSTATE.EL == EL2 then
    if SCR_EL3.NS == '0' then
        UNDEFINED;
    elsif Halted() && HaveEL(EL3) && EDSCR.SDD == '1' && boolean IMPLEMENTATION_DEFINED "EL3 trap priority when SDD == '1'" && SCR_EL3.TLOR == '1' then
        UNDEFINED;
    elsif HaveEL(EL3) && SCR_EL3.TLOR == '1' then
        if Halted() && EDSCR.SDD == '1' then
            UNDEFINED;
        else
            AArch64.SystemAccessTrap(EL3, 0x18);
    else
        return LORSA_EL1;
elsif PSTATE.EL == EL3 then
    if SCR_EL3.NS == '0' then
        UNDEFINED;
    else
        return LORSA_EL1;
              

MSR LORSA_EL1, <Xt>

op0op1CRnCRmop2
0b110b0000b10100b01000b000
if PSTATE.EL == EL0 then
    UNDEFINED;
elsif PSTATE.EL == EL1 then
    if Halted() && HaveEL(EL3) && EDSCR.SDD == '1' && boolean IMPLEMENTATION_DEFINED "EL3 trap priority when SDD == '1'" && SCR_EL3.TLOR == '1' then
        UNDEFINED;
    elsif SCR_EL3.NS == '0' then
        UNDEFINED;
    elsif EL2Enabled() && HCR_EL2.TLOR == '1' then
        AArch64.SystemAccessTrap(EL2, 0x18);
    elsif EL2Enabled() && (!HaveEL(EL3) || SCR_EL3.FGTEn == '1') && HFGWTR_EL2.LORSA_EL1 == '1' then
        AArch64.SystemAccessTrap(EL2, 0x18);
    elsif HaveEL(EL3) && SCR_EL3.TLOR == '1' then
        if Halted() && EDSCR.SDD == '1' then
            UNDEFINED;
        else
            AArch64.SystemAccessTrap(EL3, 0x18);
    else
        LORSA_EL1 = X[t];
elsif PSTATE.EL == EL2 then
    if SCR_EL3.NS == '0' then
        UNDEFINED;
    elsif Halted() && HaveEL(EL3) && EDSCR.SDD == '1' && boolean IMPLEMENTATION_DEFINED "EL3 trap priority when SDD == '1'" && SCR_EL3.TLOR == '1' then
        UNDEFINED;
    elsif HaveEL(EL3) && SCR_EL3.TLOR == '1' then
        if Halted() && EDSCR.SDD == '1' then
            UNDEFINED;
        else
            AArch64.SystemAccessTrap(EL3, 0x18);
    else
        LORSA_EL1 = X[t];
elsif PSTATE.EL == EL3 then
    if SCR_EL3.NS == '0' then
        UNDEFINED;
    else
        LORSA_EL1 = X[t];