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ICC_SRE_EL3, Interrupt Controller System Register Enable register (EL3)

The ICC_SRE_EL3 characteristics are:

Purpose

Controls whether the System register interface or the memory-mapped interface to the GIC CPU interface is used for EL3.

Configuration

AArch64 System register ICC_SRE_EL3 bits [31:0] can be mapped to AArch32 System register ICC_MSRE[31:0] , but this is not architecturally mandated.

This register is present only when HaveEL(EL3). Otherwise, direct accesses to ICC_SRE_EL3 are UNDEFINED.

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

ICC_SRE_EL3 is a 64-bit register.

Field descriptions

The ICC_SRE_EL3 bit assignments are:

6362616059585756555453525150494847464544434241403938373635343332
RES0
RES0EnableDIBDFBSRE
313029282726252423222120191817161514131211109876543210

Bits [63:4]

Reserved, RES0.

Enable, bit [3]

Enable. Enables lower Exception level access to ICC_SRE_EL1 and ICC_SRE_EL2.

EnableMeaning
0b0

EL1 accesses to ICC_SRE_EL1 trap to EL3, unless these accesses are trapped to EL2 as a result of ICC_SRE_EL2.Enable == 0.

EL2 accesses to ICC_SRE_EL1 and ICC_SRE_EL2 trap to EL3.

0b1

EL1 accesses to ICC_SRE_EL1 do not trap to EL3.

EL2 accesses to ICC_SRE_EL1 and ICC_SRE_EL2 do not trap to EL3.

If ICC_SRE_EL3.SRE is RAO/WI, an implementation is permitted to make the Enable bit RAO/WI.

If ICC_SRE_EL3.SRE is 0, the Enable bit behaves as 1 for all purposes other than reading the value of the bit.

This field resets to an architecturally UNKNOWN value.

DIB, bit [2]

Disable IRQ bypass.

DIBMeaning
0b0

IRQ bypass enabled.

0b1

IRQ bypass disabled.

In systems that do not support IRQ bypass, this bit is RAO/WI.

This field resets to 0.

DFB, bit [1]

Disable FIQ bypass.

DFBMeaning
0b0

FIQ bypass enabled.

0b1

FIQ bypass disabled.

In systems that do not support FIQ bypass, this bit is RAO/WI.

This field resets to 0.

SRE, bit [0]

System Register Enable.

SREMeaning
0b0

The memory-mapped interface must be used. Access at EL3 to any ICH_* or ICC_* register other than ICC_SRE_EL1, ICC_SRE_EL2, or ICC_SRE_EL3 is trapped to EL3

0b1

The System register interface to the ICH_* registers and the EL1, EL2, and EL3 ICC_* registers is enabled for EL3.

If software changes this bit from 1 to 0, the results are UNPREDICTABLE.

GICv3 implementations that do not require GICv2 compatibility might choose to make this bit RAO/WI.

This field resets to 0.

Accessing the ICC_SRE_EL3

This register is always System register accessible.

Accesses to this register use the following encodings:

MRS <Xt>, ICC_SRE_EL3

op0op1CRnCRmop2
0b110b1100b11000b11000b101
if PSTATE.EL == EL0 then
    UNDEFINED;
elsif PSTATE.EL == EL1 then
    UNDEFINED;
elsif PSTATE.EL == EL2 then
    UNDEFINED;
elsif PSTATE.EL == EL3 then
    return ICC_SRE_EL3;
              

MSR ICC_SRE_EL3, <Xt>

op0op1CRnCRmop2
0b110b1100b11000b11000b101
if PSTATE.EL == EL0 then
    UNDEFINED;
elsif PSTATE.EL == EL1 then
    UNDEFINED;
elsif PSTATE.EL == EL2 then
    UNDEFINED;
elsif PSTATE.EL == EL3 then
    ICC_SRE_EL3 = X[t];
              


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