[Xen-devel] Xen unstable crash on grant table debug output

[Andre Przywara <andre.przywara@xxxxxxx>]

Hi,

we see a crash of recent Xen unstable on various machines while dumping 
the "grant table usage" debug information ("# xm debug g" or 3*Ctrl+A g)
(XEN) Assertion 'gt->gt_version != 0' failed at grant_table.c:216
(XEN) ----[ Xen-4.0.0-rc6-pre  x86_64  debug=y  Not tainted ]----
(XEN) CPU:    7
(XEN) RIP:    e008:[<ffff82c480108bbc>] nr_grant_entries+0xb/0x33
(XEN) RFLAGS: 0000000000010246   CONTEXT: hypervisor
(XEN) rax: 0000000000000000   rbx: 0000000000000000   rcx: 0000000000000000
(XEN) rdx: ffffffffffffffff   rsi: 0000000000000000   rdi: ffff8301379f1d30
(XEN) rbp: ffff83005fee7e08   rsp: ffff83005fee7e08   r8:  ffff82c4801365e5
(XEN) r9:  0000000000000004   r10: 0000000000000002   r11: 0000000000000002
(XEN) r12: 0000000000000067   r13: ffff8300a6150000   r14: 0000000000000000
(XEN) r15: 00001319fbaf3b4a   cr0: 000000008005003b   cr4: 00000000000006f0
(XEN) cr3: 000000017ed5a000   cr2: ffff88016f699778
(XEN) ds: 002b   es: 002b   fs: 0000   gs: 0000   ss: e010   cs: e008
(XEN) Xen stack trace from rsp=ffff83005fee7e08:
(XEN)    ffff83005fee7e68 ffff82c480108dc4 0000000000037542 ffff82c400000019
(XEN)    000000015e0c7740 ffff8300bfbc4808 0000000000037542 ffff8300a6150000
(XEN)    0000000000000067 ffff82c480305418 ffff82c48030ca80 00001319fbaf3b4a
(XEN)    ffff83005fee7e88 ffff82c480108e41 0000000000000067 ffff82c48023f120
(XEN)    ffff83005fee7eb8 ffff82c48011079e 0000000000000002 ffff82c48023f240
(XEN)    ffff82c48023f240 ffff83005fee7f28 ffff83005fee7ed8 ffff82c48011ec6a
(XEN)    0000000000000007 ffffffffffffffff ffff83005fee7f08 ffff82c48011ea87
(XEN)    ffff83005fea0000 ffff83005fea0000 ffff83005feee000 0000000000000001
(XEN)    ffff83005fee7f18 ffff82c48011eaa0 ffff83005fee7db0 ffff82c4801f6296
(XEN)    0000000000000000 0000000000000000 0000000000000000 0000000000000000
(XEN)    0000000000000000 0000000000000004 0000000000000246 0000000000000000
(XEN)    00000001001f95d7 00000000000000d7 0000000000000000 ffffffff810053aa
(XEN)    0000000000000000 00000000deadbeef 00000000deadbeef 0000010000000000
(XEN)    ffffffff810053aa 000000000000e033 0000000000000246 ffff88017322bef8
(XEN)    000000000000e02b ffffffff0000beef ffff81002b69beef ffff81003f33beef
(XEN)    000000000001beef ffff810000000007 ffff83005fea0000
(XEN) Xen call trace:
(XEN)    [<ffff82c480108bbc>] nr_grant_entries+0xb/0x33
(XEN)    [<ffff82c480108dc4>] gnttab_usage_print+0x184/0x1c8
(XEN)    [<ffff82c480108e41>] gnttab_usage_print_all+0x39/0x61
(XEN)    [<ffff82c48011079e>] run_all_nonirq_keyhandlers+0x52/0x73
(XEN)    [<ffff82c48011ec6a>] tasklet_action+0x9a/0x122
(XEN)    [<ffff82c48011ea87>] __do_softirq+0x6c/0x77
(XEN)    [<ffff82c48011eaa0>] do_softirq+0xe/0x10
(XEN)
(XEN)
(XEN) ****************************************
(XEN) Panic on CPU 7:
(XEN) Assertion 'gt->gt_version != 0' failed at grant_table.c:216
(XEN) ****************************************
(XEN)
(XEN) Manual reset required ('noreboot' specified)

To reproduce:
* start Xen unstable HV (tried 2.6.18 Dom0)
* start a guest (we only tried HVM guests), letting them idle in grub
  suffices
* # xm debug g
<CRASH>

I haven't had time to investigate this (and am not very familiar with 
that part of the code), so any help is appreciated.
Thanks,
Andre.

--
Andre Przywara
AMD-Operating System Research Center (OSRC), Dresden, Germany
Tel: +49 351 448 3567 12
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Advanced Micro Devices GmbH
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