Comment # 24 on bug 964342 from Olaf Hering

It is hwinfo which triggers it. In src/hd/bios.c, after the (failed) attempt to
open /proc/apm it tries to mmap /dev/mem:

[   45.400599] OLH do_sys_open(1039) swapper/0[0]->init[1] /dev/mem 5
[   45.400614] ------------[ cut here ]------------
[   45.400624] WARNING: CPU: 0 PID: 1 at
/work/olaf/factory/kerncvs/kernel-stable.git/arch/x86/xen/multicalls.c:129
xen_mc_flush+0x1e8/0x1f0()
[   45.400634] Modules linked in:
[   45.400640] CPU: 0 PID: 1 Comm: init Not tainted 4.4.3-1-default+ #4
[   45.400646]  0000000000000000 ffff88003e2cbbc0 ffffffff81388701
0000000000000000
[   45.400656]  ffffffff81a3bad8 ffff88003e2cbbf8 ffffffff8107d712
ffff88003f80a2e0
[   45.400666]  0000000000000001 00007f75aad5e000 0000000000000000
00007f75aad5e000
[   45.400675] Call Trace:
[   45.400687]  [<ffffffff8101b0e5>] try_stack_unwind+0x175/0x190
[   45.400697]  [<ffffffff8101a039>] dump_trace+0x69/0x3a0
[   45.400704]  [<ffffffff8101b14b>] show_trace_log_lvl+0x4b/0x60
[   45.400711]  [<ffffffff8101a47c>] show_stack_log_lvl+0x10c/0x180
[   45.400717]  [<ffffffff8101b1e5>] show_stack+0x25/0x50
[   45.400725]  [<ffffffff81388701>] dump_stack+0x63/0x82
[   45.400734]  [<ffffffff8107d712>] warn_slowpath_common+0x82/0xc0
[   45.400741]  [<ffffffff8107d80a>] warn_slowpath_null+0x1a/0x20
[   45.400748]  [<ffffffff81006ea8>] xen_mc_flush+0x1e8/0x1f0
[   45.400756]  [<ffffffff81007805>] xen_leave_lazy_mmu+0x15/0x30
[   45.400764]  [<ffffffff811b7c2d>] remap_pfn_range+0x34d/0x430
[   45.400772]  [<ffffffff8149ef5f>] mmap_mem+0xcf/0x120
[   45.400780]  [<ffffffff811be187>] mmap_region+0x3f7/0x680
[   45.400788]  [<ffffffff811be743>] do_mmap+0x333/0x420
[   45.400797]  [<ffffffff811a4aa1>] vm_mmap_pgoff+0x91/0xc0
[   45.400804]  [<ffffffff811bcab9>] SyS_mmap_pgoff+0x1a9/0x2c0
[   45.400813]  [<ffffffff8101d19b>] SyS_mmap+0x1b/0x30
[   45.400821]  [<ffffffff816b8236>] entry_SYSCALL_64_fastpath+0x16/0x75
[   45.402389] DWARF2 unwinder stuck at entry_SYSCALL_64_fastpath+0x16/0x75
[   45.402395] 
[   45.402399] Leftover inexact backtrace:
[   45.402399] 
[   45.402408] ---[ end trace 12476ff1207380fb ]---
[   45.601203] OLH SYSC_mmap_pgoff(1472) swapper/0[0]->init[1] mmap(addr 0
length 4096 prot 1 flags 2 fd 5 offset 0 == 140143354040320
Caught signal 7!