Re: PANIC: double fault, error_code: 0x0 in 4.0.0-rc3-2, kvm related?

[Takashi Iwai]

At Mon, 23 Mar 2015 10:02:52 +0100,
Takashi Iwai wrote:
> 
> At Fri, 20 Mar 2015 19:16:53 +0100,
> Denys Vlasenko wrote:
> > Takashi, are you willing to reproduce the panic one more time,
> > with this patch? I would like to see whether oops messages
> > are more informative with it.
> 
> It can't be applied to 4.0-rc5, unfortunately.
> 
> arch/x86/kernel/entry_64.S: Assembler messages:
> arch/x86/kernel/entry_64.S:1725: Error: no such instruction: `alloc_pt_gpregs_on_stack'
> arch/x86/kernel/entry_64.S:1716: Error: invalid operands (*UND* and *UND* sections) for `+'
> scripts/Makefile.build:294: recipe for target 'arch/x86/kernel/entry_64.o' failed

I pulled tip tree on top of 4.0-rc5, built with your patch and now
succeeded to get a better message:

 kvm: zapping shadow pages for mmio generation wraparound
 kvm [5126]: vcpu0 disabled perfctr wrmsr: 0xc1 data 0xffff
 Exception on user stack 00007ffd22c23ef0: RSP: 0018:00007ffd22c23f28  EFLAGS: 00010006
 RIP: 0010:[<ffffffff8162681d>]  [<ffffffff8162681d>] netlink_attachskb+0x1d/0x1d0
 PANIC: double fault, error_code: 0x0
 CPU: 1 PID: 10819 Comm: cc1 Tainted: G        W       4.0.0-rc5-debug1+ #2
 Hardware name: Dell Inc. OptiPlex 9010/0M9KCM, BIOS A12 01/10/2013
 task: ffff8800d1b34b10 ti: ffff8800d1b30000 task.ti: ffff8800d1b30000
 RIP: 0010:[<ffffffff8162681d>]  [<ffffffff8162681d>] netlink_attachskb+0x1d/0x1d0
 RSP: 0018:00007ffd22c23f28  EFLAGS: 00010006
 RAX: 0000000000000000 RBX: 0000000000000005 RCX: 00000000c0000101
 RDX: 0000000000000000 RSI: 0000000000000001 RDI: 00007ffd22c23ef0
 RBP: 0000000000000ea7 R08: 0000000000001ea7 R09: ffffffffffffffff
 R10: 000000000309dbf8 R11: 0000000000000246 R12: 0000000000000001
 R13: 0000000000000000 R14: 0000000003026e40 R15: 000000000309cd50
 FS:  00007f89c83c2800(0000) GS:ffff88021d240000(0000) knlGS:0000000000000000
 CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
 CR2: 000000000000016d CR3: 00000000d90a0000 CR4: 00000000001427e0
 Stack:
  0000000000000ea7 0000000000000000 0000000003099c10 0000000000000ea7
  0000000000000ea7 0000000000000001 0000000003099c10 0000000000000ea7
  0000000000c84696 0000000003099c88 00007f0122c23fb8 000000000302f610
 Call Trace:
  <UNK> 
 Code: 
 10 75 ee f0 ff 42 6c 48 89 d0 5d c3 66 90 0f 1f 44 00 00 55 48 89 e5 41 56 41 55 49 89 d5 41 54 49 89 f4 53 48 89 fb 48 83 ec 30 <8b> 87 68 01 00 00 39 87 9c 01 00 00 7c 25 48 8b 87 88 04 00 00 
 Kernel panic - not syncing: Machine halted.
 CPU: 1 PID: 10819 Comm: cc1 Tainted: G        W       4.0.0-rc5-debug1+ #2
 Hardware name: Dell Inc. OptiPlex 9010/0M9KCM, BIOS A12 01/10/2013
  0000000000000000 ffff8800d1b33e28 ffffffff816f80d2 0000000000000000
  ffffffff81a22f81 ffff8800d1b33ea8 ffffffff816f2358 00000000000058d7
  0000000000000008 ffff8800d1b33eb8 ffff8800d1b33e58 ffff8800d1b33ea8
 Call Trace:
  [<ffffffff816f80d2>] dump_stack+0x4c/0x6e
  [<ffffffff816f2358>] panic+0xc0/0x1f3
  [<ffffffff81046e65>] df_debug+0x35/0x40
  [<ffffffff81003fe7>] do_double_fault+0x87/0x100
  [<ffffffff81004167>] do_userpsace_rsp_in_kernel+0x107/0x140
  [<ffffffff8162681d>] ? netlink_attachskb+0x1d/0x1d0
  [<ffffffff81703ca6>] userpsace_rsp_in_kernel+0x36/0x40
  [<ffffffff8162681d>] ? netlink_attachskb+0x1d/0x1d0


So, it seems hitting in netlink_attachskb().
I'd need to check whether this consistently hits there or just at
random.


Takashi
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