The hardware is AMD.
But what I see suggests that at this point a Local APIC timer interrupt gets
delivered to the thread. And that causes all the mess as the thread holding the
spinlock gets preempted.
Does this ring a bell to anyone?
I have seen something similar to this after about ~20 mins when doing
a current -j 16 buildworld in a guest, with the symptom being a spinlock
timeout, with one vCPU spinning in
smp_targeted_tlb_shootdown() at smp_targeted_tlb_shootdown+0x352/frame
smp_masked_invlpg() at smp_masked_invlpg+0x4c/frame 0xfffffe02c8009900
pmap_invalidate_page() at pmap_invalidate_page+0x191/frame
pmap_ts_referenced() at pmap_ts_referenced+0x7b3/frame 0xfffffe02c8009a00
vm_pageout() at vm_pageout+0xe04/frame 0xfffffe02c8009a70
... and all the others eventually spinning on that held lock.
However, NMIs are still able to get through (the post-panic ddb NMI IPI)
so the VM isn't completely locked up - either an interrupt is missed, or
a write isn't seen by the vCPU issuing the tlb shootdown.
Is there any suspect code?
Not sure yet, but the interrupt-injection path could do with a close
It seems that we set v_intr_masking bit, so the rFLAGS / eFLAGS should be
completely virtualized. So, maybe a hardware issue?
Hard to say. Running with all vCPUs pinned makes the problem go away,
but that could just mean the issue is isolated to when vCPUs migrate.
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