GitLab

The following commit:

  1fb3a8b2 ("xen/spinlock: Fix locking path engaging too soon under PVHVM.")

... moved the initalization of the kicker interrupt until after
native_cpu_up() is called.

However, when using qspinlocks, a CPU may try to kick another CPU that is
spinning (because it has not yet initialized its kicker interrupt), resulting
in the following crash during boot:

  kernel BUG at /build/linux-Ay7j_C/linux-4.4.0/drivers/xen/events/events_base.c:1210!
  invalid opcode: 0000 [#1] SMP
  ...
  RIP: 0010:[<ffffffff814c97c9>]  [<ffffffff814c97c9>] xen_send_IPI_one+0x59/0x60
  ...
  Call Trace:
   [<ffffffff8102be9e>] xen_qlock_kick+0xe/0x10
   [<ffffffff810cabc2>] __pv_queued_spin_unlock+0xb2/0xf0
   [<ffffffff810ca6d1>] ? __raw_callee_save___pv_queued_spin_unlock+0x11/0x20
   [<ffffffff81052936>] ? check_tsc_warp+0x76/0x150
   [<ffffffff81052aa6>] check_tsc_sync_source+0x96/0x160
   [<ffffffff81051e28>] native_cpu_up+0x3d8/0x9f0
   [<fff...