Subject: linux-next: boot failure after merge of the mm tree

From: Stephen Rothwell <[email-masked]>
Date: Tue, 4 Jul 2023 13:38:37 +1000

Hi all,

After merging the mm tree, today's linux-next qemu boot test (powerpc
pseries_le_defconfig) failed like this:

 Run /init as init process
 BUG: Kernel NULL pointer dereference on read at 0x00000008
 Faulting instruction address: 0xc000000000468ed0
 Oops: Kernel access of bad area, sig: 11 [#1]
 LE PAGE_SIZE=64K MMU=Hash SMP NR_CPUS=2048 NUMA pSeries
 Modules linked in:
 CPU: 0 PID: 1 Comm: init Not tainted 6.4.0-13165-g408ff5108632 #2
 Hardware name: IBM pSeries (emulated by qemu) POWER8 (raw) 0x4d0200 0xf000004 of:SLOF,HEAD pSeries
 NIP:  c000000000468ed0 LR: c000000000468410 CTR: 0000000000000000
 REGS: c00000000479b960 TRAP: 0300   Not tainted  (6.4.0-13165-g408ff5108632)
 MSR:  8000000000009033 <SF,EE,ME,IR,DR,RI,LE>  CR: 24024800  XER: 00000000
 CFAR: c00000000000db4c DAR: 0000000000000008 DSISR: 40000000 IRQMASK: 0 
 GPR00: c000000000468410 c00000000479bc00 c000000001568f00 c0000000041a6180 
 GPR04: 000000007fff8785 c00000000479bbe0 c00000000479bc98 0000000000000000 
 GPR08: ff7fffffffffefbf c00000000153cb10 c000000000432860 0000000000002000 
 GPR12: c00000000445fb08 c000000002b00000 0000000000000000 0000000000000000 
 GPR16: 0000000000000000 0000000000000000 0000000000000000 0000000000000000 
 GPR20: 0000000000000000 0000000000000000 c0000000029901a0 c00000000692d000 
 GPR24: c0000000029901a8 0000000000000075 0000000000000000 c0000000029901b0 
 GPR28: 0000000000000354 c00000000693fcf0 c00000000693fcf0 0000000000000000 
 NIP [c000000000468ed0] __handle_mm_fault+0xeb0/0x18a0
 LR [c000000000468410] __handle_mm_fault+0x3f0/0x18a0
 Call Trace:
 [c00000000479bc00] [c000000000468410] __handle_mm_fault+0x3f0/0x18a0 (unreliable)
 [c00000000479bd00] [c000000000469970] handle_mm_fault+0xb0/0x350
 [c00000000479bd50] [c0000000000894b4] ___do_page_fault+0x214/0x920
 [c00000000479bdf0] [c000000000089c70] hash__do_page_fault+0x30/0xc0
 [c00000000479be20] [c0000000000930a4] do_hash_fault+0x1d4/0x330
 [c00000000479be50] [c00000000000904c] instruction_access_common_virt+0x20c/0x210
 --- interrupt: 400 at 0x7fff878510a0
 NIP:  00007fff878510a0 LR: 0000000000000000 CTR: 0000000000000000
 REGS: c00000000479be80 TRAP: 0400   Not tainted  (6.4.0-13165-g408ff5108632)
 MSR:  800000004000d033 <SF,EE,PR,ME,IR,DR,RI,LE>  CR: 00000000  XER: 00000000
 CFAR: c00000000000d7bc IRQMASK: 0 
 GPR00: 0000000000000000 00007fffeb1b47a0 0000000000000000 0000000000000000 
 GPR04: 0000000000000000 0000000000000000 0000000000000000 0000000000000000 
 GPR08: 0000000000000000 0000000000000000 0000000000000000 0000000000000000 
 GPR12: 00007fff878510a0 0000000000000000 0000000000000000 0000000000000000 
 GPR16: 0000000000000000 0000000000000000 0000000000000000 0000000000000000 
 GPR20: 0000000000000000 0000000000000000 0000000000000000 0000000000000000 
 GPR24: 0000000000000000 0000000000000000 0000000000000000 0000000000000000 
 GPR28: 0000000000000000 0000000000000000 0000000000000000 0000000000000000 
 NIP [00007fff878510a0] 0x7fff878510a0
 LR [0000000000000000] 0x0
 --- interrupt: 400
 Code: 73e90973 4082060c 38610038 4bffe5dd 7c7fe378 73e90d73 408205ec 38610038 4bff7ad9 7fff1b78 4bfff728 eb410088 <e95a0008> 71480001 4082078c e9290038 
 ---[ end trace 0000000000000000 ]---

I don't know what caused this, but reverting the mm tree fixed the
failure.  So I have done that for today.

-- 
Cheers,
Stephen Rothwell