Re: [Xen-devel] xenoprof backtrace BUG at spinlock.c:48

[Keir Fraser <keir.xen@xxxxxxxxx>]

On 17/10/2012 18:07, "Jacob Shin" <jacob.shin@xxxxxxx> wrote:

> Hi,
> 
> When running xenoprof with backtrace (--callgraph) enabled, with HVM passive
> domain I trigger the following BUG:
> 
> It looks like there were changes in locking over time and this code path never
> kept up .. Any thoughts/hints on how to get this working again?

It's never been valid to acquire locks in NMI context, due to the potential
for deadlock. The backtrace looks quite misguided, the event should be
logged to a simple buffer and then the posting to guest memory done later in
a suitable safe context. Or the guest memory needs to be pinned and mapped
in hypervisor address space so that it can be accessed from NMI context with
no need for locks.

 -- Keir

> Thanks!
> 
> (XEN) Xen BUG at spinlock.c:48
> (XEN) ----[ Xen-4.3-unstable  x86_64  debug=y  Not tainted ]----
> (XEN) CPU:    4
> (XEN) RIP:    e008:[<ffff82c480124ad2>] check_lock+0x32/0x3e
> (XEN) RFLAGS: 0000000000010046   CONTEXT: hypervisor
> (XEN) rax: 0000000000000000   rbx: ffff8301d0111a60   rcx: 0000000000000001
> (XEN) rdx: 0000000000000000   rsi: ffff8301d0111a60   rdi: ffff8301d0111a64
> (XEN) rbp: ffff8302298afbb0   rsp: ffff8302298afbb0   r8:  0000000000000000
> (XEN) r9:  0000000000000002   r10: 0000000000000000   r11: 0000000000000000
> (XEN) r12: ffff8302298afc04   r13: ffff8301d0111a60   r14: 0000000000000001
> (XEN) r15: 0000000000000000   cr0: 0000000080050033   cr4: 00000000000406f0
> (XEN) cr3: 000000021fcfa000   cr2: 0000000000000000
> (XEN) ds: 0000   es: 0000   fs: 0000   gs: 0000   ss: 0000   cs: e008
> (XEN) Xen stack trace from rsp=ffff8302298afbb0:
> (XEN)    ffff8302298afbc8 ffff82c480124e7c ffff8302298afc84 ffff8302298afc38
> (XEN)    ffff82c4801d99c4 ffff8302298afc38 ffff82c4801ddbd5 ffff83022d995000
> (XEN)    00000002801c1003 ffff8302298afc58 ffff82c4801b66be ffff83022d995000
> (XEN)    0000000000001ff0 0000000000001ff0 0000000000000008 0000000000000001
> (XEN)    0000000000000000 ffff8302298afcb8 ffff82c4801b11c3 ffff830009258000
> (XEN)    ffff82f6045b5be0 0000000000000004 ffff830009258000 ffff8302298afd30
> (XEN)    0000000100000004 01008301d013d058 ffff8302298afd28 ffff83021fefa000
> (XEN)    0000000000001ff0 0000000000000008 ffff8302298afd30 ffff830009258000
> (XEN)    0000000000000000 ffff8302298afcc8 ffff82c4801b149d ffff8302298afcf8
> (XEN)    ffff82c4801b1520 ffff8302298afd08 0000000000001ff0 0000000000000005
> (XEN)    ffff8302298a8000 ffff8302298afd68 ffff82c48021a46f ffff8302298a8000
> (XEN)    ffff8302298a8000 00ff8302298afd38 ffff8302298afd68 ffff82c48013797f
> (XEN)    0000000000000000 000000000000e831 ffff83022d995000 ffff830009258000
> (XEN)    ffff8301eff10000 0000000000000000 0000000000000000 ffff8302298afdb8
> (XEN)    ffff82c480138acd ffff8302298afe68 000000000000e831 0000000000000000
> (XEN)    0000000000000000 ffff82c4802ff140 0000000000000000 ffff8302298afe68
> (XEN)    ffff8302298a8000 ffff8302298afe18 ffff82c480219f2f 0000000000000004
> (XEN)    000000000000e831 00000000298afde8 ffff82c400000006 ffff8302298afe58
> (XEN)    ffff8302298afe68 ffff8302298afe68 0000000000000000 0000000000000000
> (XEN)    0000000000000000 ffff8302298afe38 ffff82c4802183da 0000000000000004
> (XEN) Xen call trace:
> (XEN)    [<ffff82c480124ad2>] check_lock+0x32/0x3e
> (XEN)    [<ffff82c480124e7c>] _read_lock+0x11/0x55
> (XEN)    [<ffff82c4801d99c4>] get_page_from_gfn_p2m+0xc3/0x26a
> (XEN)    [<ffff82c4801b11c3>] __hvm_copy+0xdf/0x33c
> (XEN)    [<ffff82c4801b149d>] hvm_copy_from_guest_virt_nofault+0x15/0x17
> (XEN)    [<ffff82c4801b1520>] copy_from_user_hvm+0x81/0x9d
> (XEN)    [<ffff82c48021a46f>] xenoprof_backtrace+0x133/0x254
> (XEN)    [<ffff82c480138acd>] xenoprof_log_event+0x143/0x159
> (XEN)    [<ffff82c480219f2f>] athlon_check_ctrs+0x117/0x524
> (XEN)    [<ffff82c4802183da>] nmi_callback+0x2a/0x9e
> (XEN)    [<ffff82c48018616e>] do_nmi+0x34/0x13a
> (XEN)    [<ffff82c480224e88>] handle_ist_exception+0x58/0x60
> (XEN)    [<ffff82c4801cb2a7>] svm_stgi_label+0/0x49
> 
> 
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