mnret
Machine mode resume from the RNMI or Double Trap handler
MNRET is an M-mode-only instruction that uses the values in mnepc and mnstatus to return to the program counter, privilege mode, and virtualization mode of the interrupted context. This instruction also sets mnstatus.NMIE. If MNRET changes the privilege mode to a mode less privileged than M, it also sets mstatus.MPRV to 0. If the Zicfilp extension is implemented, then if the new privileged mode is y, MNRET sets ELP to the logical AND of yLPE (see Section 22.1.1) and mnstatus.MNPELP.
Execution
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IDL
if (CSR[mnstatus].MNPP != 2'b11) {
CSR[mstatus].MPRV = 0;
if (implemented?(ExtensionName::Smdbltrp)) {
if (xlen() == 64) {
CSR[mstatus].MDT = 1'b0;
} else {
CSR[mstatush].MDT = 1'b0;
}
}
}
CSR[mnstatus].NMIE = 1'b1;
if (CSR[mnstatus].MNPP == 2'b00) {
set_mode(PrivilegeMode::U);
} else if (CSR[mnstatus].MNPP == 2'b01) {
set_mode(PrivilegeMode::S);
} else if (CSR[mnstatus].MNPP == 2'b11) {
set_mode(PrivilegeMode::M);
}
CSR[mnstatus].MNPP = implemented?(ExtensionName::U) ? 2'b00 : 2'b11;
$pc = $bits(CSR[CSR[mnepc]]);