[Xen-users] [BUG] Xen 4.8.3: Assertion 'oc > 0' failed at mm.c:766

[Manuel Bouyer <bouyer@xxxxxxxxxxxxxxx>]

Hello,
With a Xen 4.8.3 hypervisor (debug build), NetBSD/amd64 dom0 and NetBSD/amd64
and i386 domUs, I got this assertion failure:
(XEN) Assertion 'oc > 0' failed at mm.c:766
(XEN) ----[ Xen-4.8.3nb0  x86_64  debug=y   Not tainted ]----
(XEN) CPU:    2
(XEN) RIP:    e008:[<ffff82d080177a22>] mm.c#dec_linear_entries+0x12/0x20
(XEN) RFLAGS: 0000000000010246   CONTEXT: hypervisor (d55v3)
(XEN) rax: ffffffffffff0000   rbx: 2400000000000001   rcx: 00000000001a8ce9
(XEN) rdx: 0400000000000000   rsi: 000000000000001b   rdi: ffff82e00351a540
(XEN) rbp: 0000000000000000   rsp: ffff8301bf157c30   r8:  0000000000000000
(XEN) r9:  0000000000000200   r10: 0000000000000000   r11: 0000000000000282
(XEN) r12: ffff82e003519d20   r13: ffff82e00351a540   r14: 007fffffffffffff
(XEN) r15: 0000000000000000   cr0: 000000008005003b   cr4: 00000000000026e4
(XEN) cr3: 00000001b994a000   cr2: 00000000bb6db114
(XEN) fsb: 00000000c0ebb000   gsb: 0000000000000000   gss: 0000000000000000
(XEN) ds: 0011   es: 0011   fs: 0031   gs: 0011   ss: 0000   cs: e008
(XEN) Xen code around <ffff82d080177a22> (mm.c#dec_linear_entries+0x12/0x20):
(XEN)  c1 47 1e 66 85 c0 7f 02 <0f> 0b c3 66 66 2e 0f 1f 84 00 00 00 00 00 41 54
(XEN) Xen stack trace from rsp=ffff8301bf157c30:
(XEN)    ffff82d08017bca7 00ff82d080130ead ffff8301bf157fff ffff82e003519d20
(XEN)    ffff82e00351a540 ffff8301b990b000 0000000000000001 ffff82004000e000
(XEN)    0200000000000000 ffff82d08017c6a7 00000000000001fd ffff82d08017b732
(XEN)    00000000001a8d2a 8000000100000000 ffff8301bf157fff 2400000000000001
(XEN)    2400000000000001 ffff82e00351a540 0000000000000000 007fffffffffffff
(XEN)    0000000000000001 ffff82d08017bc72 01ff8301b9bb7720 ffff8301bf157fff
(XEN)    ffff82e00351a540 0000000000000000 0000000000000000 ffff82008000c000
(XEN)    ffff8301b990b000 ffff8300bfac8000 ffff82d08017c6ef ffff82d08018642b
(XEN)    ffff8301b990b000 0000000000000001 ffffffffffffffff ffff82d000000000
(XEN)    ffff82d080184334 ffff82d08019432a 0000000000000000 ffff830100007ff0
(XEN)    ffff8300bfac8000 ffff82d0803436d0 ffff82d0803436d8 0000000700000000
(XEN)    ffff8301b990b000 ffff82e00354ef80 ffff820000000000 00007ff000000000
(XEN)    0000000000000000 0000000000000004 00000000001a8d2a 00000000001aab7e
(XEN)    ffff82008000c018 0000000000000001 00000000cd7feab4 ffff82d08025f5f4
(XEN)    0000000000000001 ffff8301bf157fff ffff82d08018b22a ffff8301bf157e34
(XEN)    00000001ffffffff ffff82008000c000 0000000000000000 00007ff000000000
(XEN)    00000004aa77cb78 cdbe8000001a8d2a ffff8301bf157f08 00000000000001a0
(XEN)    00000000c0101347 00000000deadf00d 0000000000000004 00000000deadf00d
(XEN)    ffff82d08016bf8f 0000000000007ff0 0000000000000000 0000000000000001
(XEN)    00000000cd7feaa8 ffff82d000000004 0000000200000000 ffffffff00c0bb00
(XEN) Xen call trace:
(XEN)    [<ffff82d080177a22>] mm.c#dec_linear_entries+0x12/0x20
(XEN)    [<ffff82d08017bca7>] mm.c#_put_page_type+0xe7/0x2f0
(XEN)    [<ffff82d08017c6a7>] mm.c#put_page_from_l2e+0x197/0x1d0
(XEN)    [<ffff82d08017b732>] free_page_type+0x302/0x790
(XEN)    [<ffff82d08017bc72>] mm.c#_put_page_type+0xb2/0x2f0
(XEN)    [<ffff82d08017c6ef>] put_page_type_preemptible+0xf/0x10
(XEN)    [<ffff82d08018642b>] do_mmuext_op+0x79b/0x1af0
(XEN)    [<ffff82d080184334>] do_mmu_update+0x1714/0x1920
(XEN)    [<ffff82d08019432a>] send_IPI_mask+0xa/0x10
(XEN)    [<ffff82d08018b22a>] compat_mmuext_op+0x42a/0x450
(XEN)    [<ffff82d08016bf8f>] pv_hypercall+0x39f/0x400
(XEN)    [<ffff82d080130631>] softirq.c#__do_softirq+0x11/0x90
(XEN)    [<ffff82d08024641b>] compat_hypercall+0x5b/0x60


This is a NetBSD automatic test bench, so it does a few domUs create/shutdown
(or destroy) per days, but there shouldn't be more than one domU running
at a time. This is the second time in a week that I get this panic,
but of course I can't reliably reproduce it.

-- 
Manuel Bouyer <bouyer@xxxxxxxxxxxxxxx>
     NetBSD: 26 ans d'experience feront toujours la difference
--

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