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Reduced number of bits in mcause and medeleg registers

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This commit is contained in:
David Harris 2023-03-29 07:02:09 -07:00
parent 96e3c3bea8
commit de2a0da9e9
5 changed files with 28 additions and 25 deletions
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11
src/privileged/csr.sv
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@ -55,7 +55,7 @@ module csr #(parameter
input logic [4:0] SetFflagsM, // Set floating point flag bits in FCSR
input logic [1:0] NextPrivilegeModeM, // STATUS bits updated based on next privilege mode
input logic [1:0] PrivilegeModeW, // current privilege mode
input logic [`LOG_XLEN-1:0] CauseM, // Trap cause
input logic [3:0] CauseM, // Trap cause
input logic SelHPTW, // hardware page table walker active, so base endianness on supervisor mode
// inputs for performance counters
input logic LoadStallD,
@ -79,7 +79,7 @@ module csr #(parameter
// outputs from CSRs
output logic [1:0] STATUS_MPP,
output logic STATUS_SPP, STATUS_TSR, STATUS_TVM,
output logic [`XLEN-1:0] MEDELEG_REGW,
output logic [15:0] MEDELEG_REGW,
output logic [`XLEN-1:0] SATP_REGW,
output logic [11:0] MIP_REGW, MIE_REGW, MIDELEG_REGW,
output logic STATUS_MIE, STATUS_SIE,
@ -107,7 +107,8 @@ module csr #(parameter
logic WriteMSTATUSM, WriteMSTATUSHM, WriteSSTATUSM;
logic CSRMWriteM, CSRSWriteM, CSRUWriteM;
logic WriteFRMM, WriteFFLAGSM;
logic [`XLEN-1:0] UnalignedNextEPCM, NextEPCM, NextCauseM, NextMtvalM;
logic [`XLEN-1:0] UnalignedNextEPCM, NextEPCM, NextMtvalM;
logic [4:0] NextCauseM;
logic [11:0] CSRAdrM;
logic IllegalCSRCAccessM, IllegalCSRMAccessM, IllegalCSRSAccessM, IllegalCSRUAccessM;
logic InsufficientCSRPrivilegeM;
@ -153,7 +154,7 @@ module csr #(parameter
logic VectoredM;
logic [`XLEN-1:0] TVecPlusCauseM;
assign VectoredM = InterruptM & (TVecM[1:0] == 2'b01);
assign TVecPlusCauseM = {TVecAlignedM[`XLEN-1:6], CauseM[3:0], 2'b00}; // 64-byte alignment allows concatenation rather than addition
assign TVecPlusCauseM = {TVecAlignedM[`XLEN-1:6], CauseM, 2'b00}; // 64-byte alignment allows concatenation rather than addition
mux2 #(`XLEN) trapvecmux(TVecAlignedM, TVecPlusCauseM, VectoredM, TrapVectorM);
end else
assign TrapVectorM = TVecAlignedM;
@ -196,7 +197,7 @@ module csr #(parameter
assign CSRAdrM = InstrM[31:20];
assign UnalignedNextEPCM = TrapM ? ((wfiM & IntPendingM) ? PCM+4 : PCM) : CSRWriteValM;
assign NextEPCM = `C_SUPPORTED ? {UnalignedNextEPCM[`XLEN-1:1], 1'b0} : {UnalignedNextEPCM[`XLEN-1:2], 2'b00}; // 3.1.15 alignment
assign NextCauseM = TrapM ? {InterruptM, {(`XLEN-`LOG_XLEN-1){1'b0}}, CauseM}: CSRWriteValM;
assign NextCauseM = TrapM ? {InterruptM, CauseM}: {CSRWriteValM[`XLEN-1], CSRWriteValM[3:0]};
assign NextMtvalM = TrapM ? NextFaultMtvalM : CSRWriteValM;
assign CSRMWriteM = CSRWriteM & (PrivilegeModeW == `M_MODE);
assign CSRSWriteM = CSRWriteM & (|PrivilegeModeW);

21
src/privileged/csrm.sv
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@ -69,20 +69,21 @@ module csrm #(parameter
DSCRATCH1 = 12'h7B3,
// Constants
ZERO = {(`XLEN){1'b0}},
MEDELEG_MASK = ~(ZERO | `XLEN'b1 << 11),
MEDELEG_MASK = 16'hB3FF,
MIDELEG_MASK = 12'h222 // we choose to not make machine interrupts delegable
) (
input logic clk, reset,
input logic InstrValidNotFlushedM,
input logic CSRMWriteM, MTrapM,
input logic [11:0] CSRAdrM,
input logic [`XLEN-1:0] NextEPCM, NextCauseM, NextMtvalM, MSTATUS_REGW, MSTATUSH_REGW,
input logic [`XLEN-1:0] NextEPCM, NextMtvalM, MSTATUS_REGW, MSTATUSH_REGW,
input logic [4:0] NextCauseM,
input logic [`XLEN-1:0] CSRWriteValM,
input logic [11:0] MIP_REGW, MIE_REGW,
output logic [`XLEN-1:0] CSRMReadValM, MTVEC_REGW,
output logic [`XLEN-1:0] MEPC_REGW,
output logic [31:0] MCOUNTEREN_REGW, MCOUNTINHIBIT_REGW,
output logic [`XLEN-1:0] MEDELEG_REGW,
output logic [15:0] MEDELEG_REGW,
output logic [11:0] MIDELEG_REGW,
output var logic [7:0] PMPCFG_ARRAY_REGW[`PMP_ENTRIES-1:0],
output var logic [`PA_BITS-3:0] PMPADDR_ARRAY_REGW [`PMP_ENTRIES-1:0],
@ -91,8 +92,8 @@ module csrm #(parameter
);
logic [`XLEN-1:0] MISA_REGW, MHARTID_REGW;
logic [`XLEN-1:0] MSCRATCH_REGW;
logic [`XLEN-1:0] MCAUSE_REGW, MTVAL_REGW;
logic [`XLEN-1:0] MSCRATCH_REGW, MTVAL_REGW;
logic [4:0] MCAUSE_REGW;
logic WriteMTVECM, WriteMEDELEGM, WriteMIDELEGM;
logic WriteMSCRATCHM, WriteMEPCM, WriteMCAUSEM, WriteMTVALM;
logic WriteMCOUNTERENM, WriteMCOUNTINHIBITM;
@ -150,13 +151,13 @@ module csrm #(parameter
// CSRs
flopenr #(`XLEN) MTVECreg(clk, reset, WriteMTVECM, {CSRWriteValM[`XLEN-1:2], 1'b0, CSRWriteValM[0]}, MTVEC_REGW);
if (`S_SUPPORTED) begin:deleg // DELEG registers should exist
flopenr #(`XLEN) MEDELEGreg(clk, reset, WriteMEDELEGM, CSRWriteValM & MEDELEG_MASK, MEDELEG_REGW);
flopenr #(12) MIDELEGreg(clk, reset, WriteMIDELEGM, CSRWriteValM[11:0] & MIDELEG_MASK, MIDELEG_REGW);
flopenr #(16) MEDELEGreg(clk, reset, WriteMEDELEGM, CSRWriteValM[15:0] & MEDELEG_MASK, MEDELEG_REGW);
flopenr #(12) MIDELEGreg(clk, reset, WriteMIDELEGM, CSRWriteValM[11:0] & MIDELEG_MASK, MIDELEG_REGW);
end else assign {MEDELEG_REGW, MIDELEG_REGW} = 0;
flopenr #(`XLEN) MSCRATCHreg(clk, reset, WriteMSCRATCHM, CSRWriteValM, MSCRATCH_REGW);
flopenr #(`XLEN) MEPCreg(clk, reset, WriteMEPCM, NextEPCM, MEPC_REGW);
flopenr #(`XLEN) MCAUSEreg(clk, reset, WriteMCAUSEM, NextCauseM, MCAUSE_REGW);
flopenr #(5) MCAUSEreg(clk, reset, WriteMCAUSEM, NextCauseM, MCAUSE_REGW);
if(`QEMU) assign MTVAL_REGW = `XLEN'b0; // MTVAL tied to 0 in QEMU configuration
else flopenr #(`XLEN) MTVALreg(clk, reset, WriteMTVALM, NextMtvalM, MTVAL_REGW);
flopenr #(32) MCOUNTINHIBITreg(clk, reset, WriteMCOUNTINHIBITM, CSRWriteValM[31:0], MCOUNTINHIBIT_REGW);
@ -192,13 +193,13 @@ module csrm #(parameter
MSTATUS: CSRMReadValM = MSTATUS_REGW;
MSTATUSH: CSRMReadValM = MSTATUSH_REGW;
MTVEC: CSRMReadValM = MTVEC_REGW;
MEDELEG: CSRMReadValM = MEDELEG_REGW;
MEDELEG: CSRMReadValM = {{(`XLEN-16){1'b0}}, MEDELEG_REGW};
MIDELEG: CSRMReadValM = {{(`XLEN-12){1'b0}}, MIDELEG_REGW};
MIP: CSRMReadValM = {{(`XLEN-12){1'b0}}, MIP_REGW};
MIE: CSRMReadValM = {{(`XLEN-12){1'b0}}, MIE_REGW};
MSCRATCH: CSRMReadValM = MSCRATCH_REGW;
MEPC: CSRMReadValM = MEPC_REGW;
MCAUSE: CSRMReadValM = MCAUSE_REGW;
MCAUSE: CSRMReadValM = {MCAUSE_REGW[4], {(`XLEN-5){1'b0}}, MCAUSE_REGW[3:0]};
MTVAL: CSRMReadValM = MTVAL_REGW;
MTINST: CSRMReadValM = 0; // implemented as trivial zero
MCOUNTEREN:CSRMReadValM = {{(`XLEN-32){1'b0}}, MCOUNTEREN_REGW};

9
src/privileged/csrs.sv
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@ -48,7 +48,8 @@ module csrs #(parameter
input logic InstrValidNotFlushedM,
input logic CSRSWriteM, STrapM,
input logic [11:0] CSRAdrM,
input logic [`XLEN-1:0] NextEPCM, NextCauseM, NextMtvalM, SSTATUS_REGW,
input logic [`XLEN-1:0] NextEPCM, NextMtvalM, SSTATUS_REGW,
input logic [4:0] NextCauseM,
input logic STATUS_TVM,
input logic MCOUNTEREN_TM, // TM bit (1) of MCOUNTEREN; cause illegal instruction when trying to access STIMECMP if clear
input logic [`XLEN-1:0] CSRWriteValM,
@ -73,7 +74,7 @@ module csrs #(parameter
logic WriteSCAUSEM, WriteSTVALM, WriteSATPM, WriteSCOUNTERENM;
logic WriteSTIMECMPM, WriteSTIMECMPHM;
logic [`XLEN-1:0] SSCRATCH_REGW, STVAL_REGW;
logic [`XLEN-1:0] SCAUSE_REGW;
logic [4:0] SCAUSE_REGW;
logic [63:0] STIMECMP_REGW;
// write enables
@ -93,7 +94,7 @@ module csrs #(parameter
flopenr #(`XLEN) STVECreg(clk, reset, WriteSTVECM, {CSRWriteValM[`XLEN-1:2], 1'b0, CSRWriteValM[0]}, STVEC_REGW);
flopenr #(`XLEN) SSCRATCHreg(clk, reset, WriteSSCRATCHM, CSRWriteValM, SSCRATCH_REGW);
flopenr #(`XLEN) SEPCreg(clk, reset, WriteSEPCM, NextEPCM, SEPC_REGW);
flopenr #(`XLEN) SCAUSEreg(clk, reset, WriteSCAUSEM, NextCauseM, SCAUSE_REGW);
flopenr #(5) SCAUSEreg(clk, reset, WriteSCAUSEM, NextCauseM, SCAUSE_REGW);
flopenr #(`XLEN) STVALreg(clk, reset, WriteSTVALM, NextMtvalM, STVAL_REGW);
if (`VIRTMEM_SUPPORTED)
flopenr #(`XLEN) SATPreg(clk, reset, WriteSATPM, CSRWriteValM, SATP_REGW);
@ -126,7 +127,7 @@ module csrs #(parameter
SIE: CSRSReadValM = {{(`XLEN-12){1'b0}}, MIE_REGW & 12'h222 & MIDELEG_REGW}; // only read supervisor fields
SSCRATCH: CSRSReadValM = SSCRATCH_REGW;
SEPC: CSRSReadValM = SEPC_REGW;
SCAUSE: CSRSReadValM = SCAUSE_REGW;
SCAUSE: CSRSReadValM = {SCAUSE_REGW[4], {(`XLEN-5){1'b0}}, SCAUSE_REGW[3:0]};
STVAL: CSRSReadValM = STVAL_REGW;
SATP: if (`VIRTMEM_SUPPORTED & (PrivilegeModeW == `M_MODE | ~STATUS_TVM)) CSRSReadValM = SATP_REGW;
else begin

4
src/privileged/privileged.sv
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@ -96,8 +96,8 @@ module privileged (
output logic WFIStallM // Stall in Memory stage for WFI until interrupt or timeout
);
logic [`LOG_XLEN-1:0] CauseM; // trap cause
logic [`XLEN-1:0] MEDELEG_REGW; // exception delegation CSR
logic [3:0] CauseM; // trap cause
logic [15:0] MEDELEG_REGW; // exception delegation CSR
logic [11:0] MIDELEG_REGW; // interrupt delegation CSR
logic sretM, mretM; // supervisor / machine return instruction
logic IllegalCSRAccessM; // Illegal access to CSR

8
src/privileged/trap.sv
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@ -38,7 +38,7 @@ module trap (
input logic wfiM, // wait for interrupt instruction
input logic [1:0] PrivilegeModeW, // current privilege mode
input logic [11:0] MIP_REGW, MIE_REGW, MIDELEG_REGW, // interrupt pending, enabled, and delegate CSRs
input logic [`XLEN-1:0] MEDELEG_REGW, // exception delegation SR
input logic [15:0] MEDELEG_REGW, // exception delegation SR
input logic STATUS_MIE, STATUS_SIE, // machine/supervisor interrupt enables
input logic InstrValidM, // current instruction is valid, not flushed
input logic CommittedM, CommittedF, // LSU/IFU has committed to a bus operation that can't be interrupted
@ -49,7 +49,7 @@ module trap (
output logic IntPendingM, // Interrupt is pending, might occur if enabled
output logic DelegateM, // Delegate trap to supervisor handler
output logic WFIStallM, // Stall due to WFI instruction
output logic [`LOG_XLEN-1:0] CauseM // trap cause
output logic [3:0] CauseM // trap cause
);
logic MIntGlobalEnM, SIntGlobalEnM; // Global interupt enables
@ -72,7 +72,7 @@ module trap (
assign EnabledIntsM = ({12{MIntGlobalEnM}} & PendingIntsM & ~MIDELEG_REGW | {12{SIntGlobalEnM}} & PendingIntsM & MIDELEG_REGW);
assign ValidIntsM = {12{~Committed}} & EnabledIntsM;
assign InterruptM = (|ValidIntsM) & InstrValidM; // suppress interrupt if the memory system has partially processed a request.
assign DelegateM = `S_SUPPORTED & (InterruptM ? MIDELEG_REGW[CauseM[3:0]] : MEDELEG_REGW[CauseM]) &
assign DelegateM = `S_SUPPORTED & (InterruptM ? MIDELEG_REGW[CauseM] : MEDELEG_REGW[CauseM]) &
(PrivilegeModeW == `U_MODE | PrivilegeModeW == `S_MODE);
assign WFIStallM = wfiM & ~IntPendingM;
@ -109,7 +109,7 @@ module trap (
else if (IllegalInstrFaultM) CauseM = 2;
else if (InstrMisalignedFaultM) CauseM = 0;
else if (BreakpointFaultM) CauseM = 3;
else if (EcallFaultM) CauseM = {{(`LOG_XLEN-4){1'b0}}, {2'b10}, PrivilegeModeW};
else if (EcallFaultM) CauseM = {2'b10, PrivilegeModeW};
else if (LoadMisalignedFaultM) CauseM = 4;
else if (StoreAmoMisalignedFaultM) CauseM = 6;
else if (LoadPageFaultM) CauseM = 13;