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Fix mret and mnret instructions #588

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Merged
merged 4 commits into from
Apr 8, 2025
Merged

Fix mret and mnret instructions #588

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3b9803b
Fix mret and mnret instructions to support correctly Smdbltrp (MDT bi…
ayosher Apr 2, 2025
3f60d70
MNRET instruction: improving long name and description to match Smrnm…
ayosher Apr 2, 2025
db51087
Merge branch 'main' into fix_mret_mnret
ayosher Apr 3, 2025
a892891
Merge branch 'main' into fix_mret_mnret
dhower-qc Apr 8, 2025
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9 changes: 8 additions & 1 deletion arch/inst/I/mret.yaml
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Original file line number Diff line number Diff line change
Expand Up @@ -14,9 +14,16 @@ access:
encoding:
match: "00110000001000000000000001110011"
operation(): |
if (implemented?(ExtensionName::S) && CSR[mstatus].MPP != 2'b11) {
if (CSR[mstatus].MPP != 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[mstatus].MIE = CSR[mstatus].MPIE;
CSR[mstatus].MPIE = 1;
if (CSR[mstatus].MPP == 2'b00) {
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18 changes: 15 additions & 3 deletions arch/inst/Smrnmi/mnret.yaml
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Original file line number Diff line number Diff line change
Expand Up @@ -3,9 +3,13 @@
$schema: inst_schema.json#
kind: instruction
name: mnret
long_name: No synopsis available.
long_name: Machine mode resume from the RNMI or Double Trap handler.
description: |
No description available.
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.
definedBy: Smrnmi
assembly: mnret
encoding:
Expand All @@ -18,9 +22,17 @@ access:
vu: always
data_independent_timing: false
operation(): |
if (implemented?(ExtensionName::S) && CSR[mstatus].MPP != 2'b11) {
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) {
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