Re: [per_cpu_ptr_to_phys] PANIC: early exception 0x0d IP 10:ffffffffa892f15f error 0 cr2 0xffff88001fbff000

[Dennis Zhou <dennisszhou@gmail.com>]

Hi,

On Wed, Apr 18, 2018 at 09:55:53PM +0800, Fengguang Wu wrote:
> 
> Hello,
> 
> FYI here is a slightly different boot error in mainline kernel 4.17.0-rc1.
> It also dates back to v4.16 .
> 
> It occurs in 4 out of 4 boots.
> 
> [    0.000000] Built 1 zonelists, mobility grouping on.  Total pages: 128873
> [    0.000000] Kernel command line: root=/dev/ram0 hung_task_panic=1 debug apic=debug sysrq_always_enabled rcupdate.rcu_cpu_stall_timeout=100 net.ifnames=0 printk.devkmsg=on panic=-1 softlockup_panic=1 nmi_watchdog=panic oops=panic load_ramdisk=2 prompt_ramdisk=0 drbd.minor_count=8 systemd.log_level=err ignore_loglevel console=tty0 earlyprintk=ttyS0,115200 console=ttyS0,115200 vga=normal rw link=/kbuild-tests/run-queue/kvm/x86_64-randconfig-a0-04172313/linux-devel:devel-hourly-2018041714:60cc43fc888428bb2f18f08997432d426a243338/.vmlinuz-60cc43fc888428bb2f18f08997432d426a243338-20180418000325-19:yocto-lkp-nhm-dp2-4 branch=linux-devel/devel-hourly-2018041714 BOOT_IMAGE=/pkg/linux/x86_64-randconfig-a0-04172313/gcc-7/60cc43fc888428bb2f18f08997432d426a243338/vmlinuz-4.17.0-rc1 drbd.minor_count=8 rcuperf.shutdown=0
> [    0.000000] sysrq: sysrq always enabled.
> [    0.000000] Dentry cache hash table entries: 65536 (order: 7, 524288 bytes)
> [    0.000000] Inode-cache hash table entries: 32768 (order: 6, 262144 bytes)
> PANIC: early exception 0x0d IP 10:ffffffffa892f15f error 0 cr2 0xffff88001fbff000
> [    0.000000] CPU: 0 PID: 0 Comm: swapper Tainted: G                T 4.17.0-rc1 #238
> [    0.000000] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.10.2-1 04/01/2014
> [    0.000000] RIP: 0010:per_cpu_ptr_to_phys+0x16a/0x298:
> 						__section_mem_map_addr at include/linux/mmzone.h:1188
> 						 (inlined by) per_cpu_ptr_to_phys at mm/percpu.c:1849
> [    0.000000] RSP: 0000:ffffffffab407e50 EFLAGS: 00010046 ORIG_RAX: 0000000000000000
> [    0.000000] RAX: dffffc0000000000 RBX: ffff88001f17c340 RCX: 000000000000000f
> [    0.000000] RDX: 0000000000000000 RSI: 0000000000000001 RDI: ffffffffacfbf580
> [    0.000000] RBP: ffffffffab40d000 R08: fffffbfff57c4eca R09: 0000000000000000
> [    0.000000] R10: ffff880015421000 R11: fffffbfff57c4ec9 R12: 0000000000000000
> [    0.000000] R13: ffff88001fb03ff8 R14: ffff88001fc051c0 R15: 0000000000000000
> [    0.000000] FS:  0000000000000000(0000) GS:ffffffffab4c5000(0000) knlGS:0000000000000000
> [    0.000000] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> [    0.000000] CR2: ffff88001fbff000 CR3: 000000001a06c000 CR4: 00000000000006b0
> [    0.000000] Call Trace:
> [    0.000000]  setup_cpu_entry_areas+0x7b/0x27b:
> 						setup_cpu_entry_area at arch/x86/mm/cpu_entry_area.c:104
> 						 (inlined by) setup_cpu_entry_areas at arch/x86/mm/cpu_entry_area.c:177
> [    0.000000]  trap_init+0xb/0x13d:
> 						trap_init at arch/x86/kernel/traps.c:949
> [    0.000000]  start_kernel+0x2a5/0x91d:
> 						mm_init at init/main.c:519
> 						 (inlined by) start_kernel at init/main.c:589
> [    0.000000]  ? thread_stack_cache_init+0x6/0x6
> [    0.000000]  ? memcpy_orig+0x16/0x110:
> 						memcpy_orig at arch/x86/lib/memcpy_64.S:77
> [    0.000000]  ? x86_family+0x5/0x1d:
> 						x86_family at arch/x86/lib/cpu.c:8
> [    0.000000]  ? load_ucode_bsp+0x42/0x13e:
> 						load_ucode_bsp at arch/x86/kernel/cpu/microcode/core.c:183
> [    0.000000]  secondary_startup_64+0xa5/0xb0:
> 						secondary_startup_64 at arch/x86/kernel/head_64.S:242
> [    0.000000] Code: 78 06 00 49 8b 45 00 48 85 c0 74 a5 49 c1 ec 28 41 81 e4 e0 0f 00 00 49 01 c4 4c 89 e2 48 b8 00 00 00 00 00 fc ff df 48 c1 ea 03 <80> 3c 02 00 74 08 4c 89 e7 e8 63 78 06 00 49 8b 04 24 81 e5 ff
> BUG: kernel hang in boot stage
> 

I spent some time bisecting this one and it seemse to be an intermittent
issue starting with this commit for me:
c9e97a1997, mm: initialize pages on demand during boot. The prior
commit, 3a2d7fa8a3, did not run into this issue after 10+ boots.

I don't have that much time right now, nor the expertise with this code.
Pavel could you take a look at this?

Thanks,
Dennis