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Published
20 hours ago •
lowRISC
lowRISC
[dv] Exception divergence using MML PMP mode
I'm seeing a divergence between Spike and Ibex when in MML mode and setting region 0 to read only. Spike throws a trap and Ibex zeroes out a destination register. I'm not sure if this is an issue with Spike, Ibex or with the UVM comparison.
Observed Behavior
Cosimulation result:
name: riscv_epmp_mml_read_only_test
seed: 14822
binary: out/run/riscv_epmp_mml_read_only_test.14822/test.o
uvm_log: out/run/riscv_epmp_mml_read_only_test.14822/rtl.log
rtl_trace: out/run/riscv_epmp_mml_read_only_test.14822/trace_core_00000000.log
rtl_trace_csv: out/run/riscv_epmp_mml_read_only_test.14822/trace_core_00000000.log.csv
iss_trace:
iss_trace_csv:
en_cosim: True
cosim_trace:
cosim_trace_csv:
comparison_log:
passed: False
failure_message: |-
UVM_FATAL /home/mvdmaas/ibex/dv/uvm/core_ibex/common/ibex_cosim_agent/ibex_cosim_scoreboard.sv(131) @ 7304: uvm_test_top.env.cosim_agent.scoreboard [ibex_cosim_agent_pkg::ibex_cosim_scoreboard.run_cosim_rvfi] Cosim mismatch Synchronous trap was expected at ISS PC: 80001900 but DUT didn't report one at PC 80000118
[FAILED]: sim error seen
Ibex RVFI trace:
Time Cycle PC Insn Decoded instruction Register and memory contents
2524 24 80000080 400015b7 lui x11,0x40001 x11=0x40001000
2864 41 80000084 10658593 addi x11,x11,262 x11:0x40001000 x11=0x40001106
3004 48 80000088 30159073 csrrw x0,misa,x11 x11:0x40001106 x0=0x00000000
3024 49 8000008c 0002c397 auipc x7,0x2c x7=0x8002c08c
3444 70 80000090 c5838393 addi x7,x7,-936 x7:0x8002c08c x7=0x8002bce4
3724 84 80000094 00002597 auipc x11,0x2 x11=0x80002094
3744 85 80000098 86c58593 addi x11,x11,-1940 x11:0x80002094 x11=0x80001900
3944 95 8000009c 0015e593 ori x11,x11,1 x11:0x80001900 x11=0x80001901
4364 116 800000a0 30559073 csrrw x0,mtvec,x11 x11:0x80001901 x0=0x00000000
4384 117 800000a4 00002b17 auipc x22,0x2 x22=0x800020a4
4404 118 800000a8 2f0b0b13 addi x22,x22,752 x22:0x800020a4 x22=0x80002394
4424 119 800000ac 002b5b13 srli x22,x22,0x2 x22:0x80002394 x22=0x200008e5
4584 127 800000b0 3b0b1073 csrrw x0,pmpaddr0,x22 x22:0x200008e5 x0=0x00000000
4604 128 800000b4 74725073 csrrwi x0,0x747,4 x0=0x00000000
4924 144 800000b8 08c00b13 addi x22,x0,140 x0:0x00000000 x22=0x0000008c
4944 145 800000bc 3a0b1073 csrrw x0,pmpcfg0,x22 x22:0x0000008c x0=0x00000000
4964 146 800000c0 7472d073 csrrwi x0,0x747,5 x0=0x00000000
4984 147 800000c4 00002b17 auipc x22,0x2 x22=0x800020c4
5024 149 800000c8 2d0b0b13 addi x22,x22,720 x22:0x800020c4 x22=0x80002394
5124 154 800000cc 6589 c.lui x11,0x2 x11=0x00002000
5544 175 800000ce 66658593 addi x11,x11,1638 x11:0x00002000 x11=0x00002666
5564 176 800000d2 9b2e c.add x22,x11 x22:0x80002394 x11:0x00002666 x22=0x800049fa
5584 177 800000d4 002b5b13 srli x22,x22,0x2 x22:0x800049fa x22=0x2000127e
5604 178 800000d8 3b1b1073 csrrw x0,pmpaddr1,x22 x22:0x2000127e x0=0x00000000
5664 181 800000dc 00002b17 auipc x22,0x2 x22=0x800020dc
5804 188 800000e0 2b8b0b13 addi x22,x22,696 x22:0x800020dc x22=0x80002394
5824 189 800000e4 6595 c.lui x11,0x5 x11=0x00005000
5944 195 800000e6 ccc58593 addi x11,x11,-820 x11:0x00005000 x11=0x00004ccc
5964 196 800000ea 9b2e c.add x22,x11 x22:0x80002394 x11:0x00004ccc x22=0x80007060
6364 216 800000ec 002b5b13 srli x22,x22,0x2 x22:0x80007060 x22=0x20001c18
6384 217 800000f0 3b2b1073 csrrw x0,pmpaddr2,x22 x22:0x20001c18 x0=0x00000000
6644 230 800000f4 00002b17 auipc x22,0x2 x22=0x800020f4
6704 233 800000f8 2a0b0b13 addi x22,x22,672 x22:0x800020f4 x22=0x80002394
6724 234 800000fc 659d c.lui x11,0x7 x11=0x00007000
6744 235 800000fe 33258593 addi x11,x11,818 x11:0x00007000 x11=0x00007332
6764 236 80000102 9b2e c.add x22,x11 x22:0x80002394 x11:0x00007332 x22=0x800096c6
6784 237 80000104 002b5b13 srli x22,x22,0x2 x22:0x800096c6 x22=0x200025b1
6924 244 80000108 3b3b1073 csrrw x0,pmpaddr3,x22 x22:0x200025b1 x0=0x00000000
7104 253 8000010c 8f8f9b37 lui x22,0x8f8f9 x22=0x8f8f9000
7124 254 80000110 f8fb0b13 addi x22,x22,-113 x22:0x8f8f9000 x22=0x8f8f8f8f
7264 261 80000114 3a0b1073 csrrw x0,pmpcfg0,x22 x22:0x8f8f8f8f x0=0x00000000
7284 262 80000118 00002b17 auipc x22,0x2 x22=0x80002118
7304 263 8000011c 27cb0b13 addi x0,x0,636 x0:0x00000000 x0=0x00000000
Spike RVFI trace:
core 0: 0x80000080 (0x400015b7) lui a1, 0x40001
core 0: 3 0x80000080 (0x400015b7) x11 0x40001000
core 0: 0x80000084 (0x10658593) addi a1, a1, 262
core 0: 3 0x80000084 (0x10658593) x11 0x40001106
core 0: 0x80000088 (0x30159073) csrw misa, a1
core 0: 3 0x80000088 (0x30159073) c769_misa 0x40901104
core 0: 0x8000008c (0x0002c397) auipc t2, 0x2c
core 0: 3 0x8000008c (0x0002c397) x7 0x8002c08c
core 0: 0x80000090 (0xc5838393) addi t2, t2, -936
core 0: 3 0x80000090 (0xc5838393) x7 0x8002bce4
core 0: 0x80000094 (0x00002597) auipc a1, 0x2
core 0: 3 0x80000094 (0x00002597) x11 0x80002094
core 0: 0x80000098 (0x86c58593) addi a1, a1, -1940
core 0: 3 0x80000098 (0x86c58593) x11 0x80001900
core 0: 0x8000009c (0x0015e593) ori a1, a1, 1
core 0: 3 0x8000009c (0x0015e593) x11 0x80001901
core 0: 0x800000a0 (0x30559073) csrw mtvec, a1
core 0: 3 0x800000a0 (0x30559073) c773_mtvec 0x80001901
core 0: 0x800000a4 (0x00002b17) auipc s6, 0x2
core 0: 3 0x800000a4 (0x00002b17) x22 0x800020a4
core 0: 0x800000a8 (0x2f0b0b13) addi s6, s6, 752
core 0: 3 0x800000a8 (0x2f0b0b13) x22 0x80002394
core 0: 0x800000ac (0x002b5b13) srli s6, s6, 2
core 0: 3 0x800000ac (0x002b5b13) x22 0x200008e5
core 0: 0x800000b0 (0x3b0b1073) csrw pmpaddr0, s6
core 0: 3 0x800000b0 (0x3b0b1073) c944_pmpaddr0 0x200008e5
core 0: 0x800000b4 (0x74725073) csrwi mseccfg, 4
core 0: 3 0x800000b4 (0x74725073) c1863_mseccfg 0x00000004
core 0: 0x800000b8 (0x08c00b13) li s6, 140
core 0: 3 0x800000b8 (0x08c00b13) x22 0x0000008c
core 0: 0x800000bc (0x3a0b1073) csrw pmpcfg0, s6
core 0: 3 0x800000bc (0x3a0b1073) c928_pmpcfg0 0x0000008c
core 0: 0x800000c0 (0x7472d073) csrwi mseccfg, 5
core 0: 3 0x800000c0 (0x7472d073) c1863_mseccfg 0x00000005
core 0: 0x800000c4 (0x00002b17) auipc s6, 0x2
core 0: 3 0x800000c4 (0x00002b17) x22 0x800020c4
core 0: 0x800000c8 (0x2d0b0b13) addi s6, s6, 720
core 0: 3 0x800000c8 (0x2d0b0b13) x22 0x80002394
core 0: 0x800000cc (0x00006589) c.lui a1, 0x2
core 0: 3 0x800000cc (0x6589) x11 0x00002000
core 0: 0x800000ce (0x66658593) addi a1, a1, 1638
core 0: 3 0x800000ce (0x66658593) x11 0x00002666
core 0: 0x800000d2 (0x00009b2e) c.add s6, a1
core 0: 3 0x800000d2 (0x9b2e) x22 0x800049fa
core 0: 0x800000d4 (0x002b5b13) srli s6, s6, 2
core 0: 3 0x800000d4 (0x002b5b13) x22 0x2000127e
core 0: 0x800000d8 (0x3b1b1073) csrw pmpaddr1, s6
core 0: 3 0x800000d8 (0x3b1b1073) c945_pmpaddr1 0x2000127e
core 0: 0x800000dc (0x00002b17) auipc s6, 0x2
core 0: 3 0x800000dc (0x00002b17) x22 0x800020dc
core 0: 0x800000e0 (0x2b8b0b13) addi s6, s6, 696
core 0: 3 0x800000e0 (0x2b8b0b13) x22 0x80002394
core 0: 0x800000e4 (0x00006595) c.lui a1, 0x5
core 0: 3 0x800000e4 (0x6595) x11 0x00005000
core 0: 0x800000e6 (0xccc58593) addi a1, a1, -820
core 0: 3 0x800000e6 (0xccc58593) x11 0x00004ccc
core 0: 0x800000ea (0x00009b2e) c.add s6, a1
core 0: 3 0x800000ea (0x9b2e) x22 0x80007060
core 0: 0x800000ec (0x002b5b13) srli s6, s6, 2
core 0: 3 0x800000ec (0x002b5b13) x22 0x20001c18
core 0: 0x800000f0 (0x3b2b1073) csrw pmpaddr2, s6
core 0: 3 0x800000f0 (0x3b2b1073) c946_pmpaddr2 0x20001c18
core 0: 0x800000f4 (0x00002b17) auipc s6, 0x2
core 0: 3 0x800000f4 (0x00002b17) x22 0x800020f4
core 0: 0x800000f8 (0x2a0b0b13) addi s6, s6, 672
core 0: 3 0x800000f8 (0x2a0b0b13) x22 0x80002394
core 0: 0x800000fc (0x0000659d) c.lui a1, 0x7
core 0: 3 0x800000fc (0x659d) x11 0x00007000
core 0: 0x800000fe (0x33258593) addi a1, a1, 818
core 0: 3 0x800000fe (0x33258593) x11 0x00007332
core 0: 0x80000102 (0x00009b2e) c.add s6, a1
core 0: 3 0x80000102 (0x9b2e) x22 0x800096c6
core 0: 0x80000104 (0x002b5b13) srli s6, s6, 2
core 0: 3 0x80000104 (0x002b5b13) x22 0x200025b1
core 0: 0x80000108 (0x3b3b1073) csrw pmpaddr3, s6
core 0: 3 0x80000108 (0x3b3b1073) c947_pmpaddr3 0x200025b1
core 0: 0x8000010c (0x8f8f9b37) lui s6, 0x8f8f9
core 0: 3 0x8000010c (0x8f8f9b37) x22 0x8f8f9000
core 0: 0x80000110 (0xf8fb0b13) addi s6, s6, -113
core 0: 3 0x80000110 (0xf8fb0b13) x22 0x8f8f8f8f
core 0: 0x80000114 (0x3a0b1073) csrw pmpcfg0, s6
core 0: 3 0x80000114 (0x3a0b1073) c928_pmpcfg0 0x8f8f8f8f
core 0: exception trap_instruction_access_fault, epc 0x80000118
core 0: tval 0x80000118
Expected Behavior
Not sure if it's a bug in Spike, Ibex or the cosimulation environment
Steps to reproduce the issue
Using the following commands from the root of the ibex repo:
cd dv/uvm/core_ibex
make -j7 --keep-going IBEX_CONFIG=opentitan ITERATIONS=1 SEED=14822 TEST=riscv_epmp_mml_read_only_test WAVES=0 COV=0
My Environment
EDA tool and version:
Using Spike version ibex_cosim on commit: 9af9730baf7b956c3072c1b436d867aca5ef8f4c
Operating system:
Ubuntu Linux 20.04
Version of the Ibex source code:
Currently running inside this PR: https://github.com/lowRISC/ibex/pull/1695
Okay I think I understood what's going on. The first problem is about how we let RVFI know that there is a problem with the issued instruction. However, when I fixed that locally I also came across another problem in which we didn't let ID/EX stage know that the current instruction of it has a PMP error -we actually set the flag but it's late. However, even if I do those two fixes we will be stuck with the problem of having infinite loops coming from the nature of how we configure PMP regions. Same infinite loop happens in pmp_full_random_test as well.
P.S. I think if we set timeout value for these tests to a reasonable time, encountering infinite loops would be fine.
Closing this because the remaining issue of infinite loops is captured in this issue: https://github.com/lowRISC/ibex/issues/1823