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FABRIC.md: item 4.5d -- Finding 3 (muldiv64) root-caused and fixed via QEMU tracing, Finding 4 blocks

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Used QEMU-side instrumentation (-d int tracing, plus a working chardev-based
monitor -- the older bareword -monitor syntax silently fails on QEMU
10.2.1) as directed. The PM Timer "stall" was never a hang: it was a #DE
divide error cascading to a triple fault, which -no-reboot converts into a
silent clean QEMU exit -- indistinguishable from a hang without tracing,
and why arch_relax() (solving a hang that didn't exist) had no effect.
Root cause and fix documented in full (also see commit b43e51a).

With the fix, amd64 boot at -O2 now proceeds far past the original stall --
through capsule birth and into Hermes's word registration -- before hitting
a second, different fault (Finding 4): a direct #GP at IDT index 32
(APIC_TIMER_VECTOR), not yet root-caused. Same silent-triple-fault-exit
shape, so this was very likely bundled into "the hang" before tracing
distinguished the two separate bugs.

-O2 reverted again (uncommitted); muldiv64's fix is kept, real and
independently verified at unchanged -O0 on all three architectures.
Routine three-arch artifacts from this session's verification runs
included.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
This commit is contained in:
Robert Allan James
2026-08-11 12:17:23 -04:00
co-authored by Claude Sonnet 5
parent b43e51a95d
commit 1c5e926c3f
18 changed files with 104344 additions and 77 deletions
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experiments/bare_metal/latest/riscv64.csv
+20 -20
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@@ -76,35 +76,35 @@ tick_number,elapsed_ns,tick_interval_ns,cache_hits_delta,bucket_hits_delta,word_
2,20000,10000,0,0,78,10,7,4096,0,0,0,13,65536,0,0,65536,0,0
3,30000,10000,0,0,101,13,7,4096,0,0,0,14,65536,0,0,65536,0,0
4,40000,10000,0,0,63,19,8,4096,0,0,0,15,65536,0,0,65536,0,0
5,50000,10000,0,0,92,25,8,4096,2,0,0,18,65536,0,0,65536,0,0
6,60000,10000,0,0,64,27,8,4096,2,0,0,19,65536,0,0,65536,0,0
5,50000,10000,0,0,92,25,8,4096,2,0,0,17,65536,0,0,65536,0,0
6,60000,10000,0,0,64,27,8,4096,2,0,0,18,65536,0,0,65536,0,0
7,70000,10000,0,0,228,32,8,4096,210,0,0,26,65536,0,0,65536,0,0
8,80000,10000,0,0,256,34,9,4096,466,0,0,34,65536,0,0,65536,0,0
9,90000,10000,0,0,256,36,10,4096,722,0,0,41,65536,0,0,65536,0,0
9,90000,10000,0,0,256,36,10,4096,722,0,0,42,65536,0,0,65536,0,0
10,100000,10000,0,0,256,36,11,4096,978,0,0,49,65536,0,0,65536,0,0
11,110000,10000,0,0,256,36,11,4096,1234,0,0,57,65536,0,0,65536,0,0
12,120000,10000,0,0,256,36,12,4096,1490,0,0,64,65536,0,0,65536,0,0
13,130000,10000,0,0,256,37,12,4096,1746,0,0,72,65536,0,0,65536,0,0
14,140000,10000,0,0,230,39,12,4096,1949,0,0,79,65536,0,0,65536,0,0
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20,200000,10000,0,0,256,41,17,4096,3480,0,0,128,65536,0,1,65536,0,0
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23,230000,10000,0,0,256,41,19,4096,4096,0,0,150,65536,0,1,65536,0,0
24,240000,10000,0,0,256,41,20,4096,4096,0,0,158,65536,0,1,65536,0,0
25,250000,10000,0,0,256,43,20,2048,2048,0,0,166,65536,0,1,65536,0,0
26,260000,10000,0,0,256,45,21,2048,2048,0,0,174,65536,0,1,65536,0,0
27,270000,10000,0,0,256,45,22,1024,1024,0,0,181,65536,0,1,65536,0,0
28,280000,10000,0,0,256,45,23,1024,1024,0,0,189,65536,0,1,65536,0,0
29,290000,10000,0,0,256,45,24,512,512,0,0,197,65536,0,1,65536,0,0
30,300000,10000,0,0,256,45,24,512,512,0,0,204,65536,0,1,65536,0,0
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34,340000,10000,0,0,256,45,27,256,256,0,0,238,65536,0,1,65536,0,0
35,350000,10000,0,0,256,45,28,256,256,0,0,246,65536,0,1,65536,0,0
36,360000,10000,0,0,256,45,29,256,256,0,0,253,65536,0,1,65536,0,0
23,230000,10000,0,0,256,41,19,4096,4096,0,0,151,65536,0,1,65536,0,0
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31,310000,10000,0,0,256,45,25,256,256,0,0,216,65536,0,1,65536,0,0
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35,350000,10000,0,0,256,45,28,256,256,0,0,249,65536,0,1,65536,0,0
36,360000,10000,0,0,256,45,29,256,256,0,0,257,65536,0,1,65536,0,0
1 tick_number elapsed_ns tick_interval_ns cache_hits_delta bucket_hits_delta word_executions_delta hot_word_count avg_word_heat_q48 window_width actual_window_size predicted_label_hits jitter_bits apic_ticks time_trust_q48 variance_q48 vm_call_depth_max hera_heat_q48 hermes_heat_q48 artemis_heat_q48
76 2 20000 10000 0 0 78 10 7 4096 0 0 0 13 65536 0 0 65536 0 0
77 3 30000 10000 0 0 101 13 7 4096 0 0 0 14 65536 0 0 65536 0 0
78 4 40000 10000 0 0 63 19 8 4096 0 0 0 15 65536 0 0 65536 0 0
79 5 50000 10000 0 0 92 25 8 4096 2 0 0 18 17 65536 0 0 65536 0 0
80 6 60000 10000 0 0 64 27 8 4096 2 0 0 19 18 65536 0 0 65536 0 0
81 7 70000 10000 0 0 228 32 8 4096 210 0 0 26 65536 0 0 65536 0 0
82 8 80000 10000 0 0 256 34 9 4096 466 0 0 34 65536 0 0 65536 0 0
83 9 90000 10000 0 0 256 36 10 4096 722 0 0 41 42 65536 0 0 65536 0 0
84 10 100000 10000 0 0 256 36 11 4096 978 0 0 49 65536 0 0 65536 0 0
85 11 110000 10000 0 0 256 36 11 4096 1234 0 0 57 65536 0 0 65536 0 0
86 12 120000 10000 0 0 256 36 12 4096 1490 0 0 64 65536 0 0 65536 0 0
87 13 130000 10000 0 0 256 37 12 4096 1746 0 0 72 65536 0 0 65536 0 0
88 14 140000 10000 0 0 230 39 12 4096 1949 0 0 79 65536 0 0 65536 0 0
89 15 150000 10000 0 0 256 39 13 4096 2204 0 0 87 65536 0 0 65536 0 0
90 16 160000 10000 0 0 256 39 14 4096 2459 0 0 94 95 65536 0 0 65536 0 0
91 17 170000 10000 0 0 256 39 15 4096 2713 0 0 102 65536 0 0 65536 0 0
92 18 180000 10000 0 0 256 39 15 4096 2969 0 0 110 65536 0 0 65536 0 0
93 19 190000 10000 0 0 256 39 16 4096 3224 0 0 119 120 65536 0 1 65536 0 0
94 20 200000 10000 0 0 256 41 17 4096 3480 0 0 127 128 65536 0 1 65536 0 0
95 21 210000 10000 0 0 256 41 17 4096 3736 0 0 135 65536 0 1 65536 0 0
96 22 220000 10000 0 0 256 41 18 4096 3992 0 0 143 65536 0 1 65536 0 0
97 23 230000 10000 0 0 256 41 19 4096 4096 0 0 150 151 65536 0 1 65536 0 0
98 24 240000 10000 0 0 256 41 20 4096 4096 0 0 158 159 65536 0 1 65536 0 0
99 25 250000 10000 0 0 256 43 20 2048 2048 0 0 166 167 65536 0 1 65536 0 0
100 26 260000 10000 0 0 256 45 21 2048 2048 0 0 174 176 65536 0 1 65536 0 0
101 27 270000 10000 0 0 256 45 22 1024 1024 0 0 181 184 65536 0 1 65536 0 0
102 28 280000 10000 0 0 256 45 23 1024 1024 0 0 189 192 65536 0 1 65536 0 0
103 29 290000 10000 0 0 256 45 24 512 512 0 0 197 199 65536 0 1 65536 0 0
104 30 300000 10000 0 0 256 45 24 512 512 0 0 204 208 65536 0 1 65536 0 0
105 31 310000 10000 0 0 256 45 25 256 256 0 0 212 216 65536 0 1 65536 0 0
106 32 320000 10000 0 0 255 45 26 256 256 0 0 222 226 65536 0 1 65536 0 0
107 33 330000 10000 0 0 256 45 27 256 256 0 0 230 233 65536 0 1 65536 0 0
108 34 340000 10000 0 0 256 45 27 256 256 0 0 238 241 65536 0 1 65536 0 0
109 35 350000 10000 0 0 256 45 28 256 256 0 0 246 249 65536 0 1 65536 0 0
110 36 360000 10000 0 0 256 45 29 256 256 0 0 253 257 65536 0 1 65536 0 0