linux_dsm_epyc7002/arch/powerpc
Nicholas Piggin 6fcd6baa90 powerpc/powernv: Use kernel crash path for machine checks
There are quite a few machine check exceptions that can be caused by
kernel bugs. To make debugging easier, use the kernel crash path in
cases of synchronous machine checks that occur in kernel mode, if that
would not result in the machine going straight to panic or crash dump.

There is a downside here that die()ing the process in kernel mode can
still leave the system unstable. panic_on_oops will always force the
system to fail-stop, so systems where that behaviour is important will
still do the right thing.

As a test, when triggering an i-side 0111b error (ifetch from foreign
address) in kernel mode process context on POWER9, the kernel currently
dies quickly like this:

  Severe Machine check interrupt [Not recovered]
    NIP [ffff000000000000]: 0xffff000000000000
    Initiator: CPU
    Error type: Real address [Instruction fetch (foreign)]
  [  127.426651616,0] OPAL: Reboot requested due to Platform error.
      Effective[  127.426693712,3] OPAL: Reboot requested due to Platform error. address: ffff000000000000
  opal: Reboot type 1 not supported
  Kernel panic - not syncing: PowerNV Unrecovered Machine Check
  CPU: 56 PID: 4425 Comm: syscall Tainted: G   M            4.12.0-rc1-13857-ga4700a261072-dirty #35
  Call Trace:
  [  128.017988928,4] IPMI: BUG: Dropping ESEL on the floor due to
    buggy/mising code in OPAL for this BMC
    Rebooting in 10 seconds..
  Trying to free IRQ 496 from IRQ context!

After this patch, the process is killed and the kernel continues with
this message, which gives enough information to identify the offending
branch (i.e., with CFAR):

  Severe Machine check interrupt [Not recovered]
    NIP [ffff000000000000]: 0xffff000000000000
    Initiator: CPU
    Error type: Real address [Instruction fetch (foreign)]
      Effective address: ffff000000000000
  Oops: Machine check, sig: 7 [#1]
  SMP NR_CPUS=2048
  NUMA
  PowerNV
  Modules linked in: iptable_mangle ipt_MASQUERADE nf_nat_masquerade_ipv4 ...
  CPU: 22 PID: 4436 Comm: syscall Tainted: G   M            4.12.0-rc1-13857-ga4700a261072-dirty #36
  task: c000000932300000 task.stack: c000000932380000
  NIP: ffff000000000000 LR: 00000000217706a4 CTR: ffff000000000000
  REGS: c00000000fc8fd80 TRAP: 0200   Tainted: G   M             (4.12.0-rc1-13857-ga4700a261072-dirty)
  MSR: 90000000001c1003 <SF,HV,ME,RI,LE>
    CR: 24000484  XER: 20000000
  CFAR: c000000000004c80 DAR: 0000000021770a90 DSISR: 0a000000 SOFTE: 1
  GPR00: 0000000000001ebe 00007fffce4818b0 0000000021797f00 0000000000000000
  GPR04: 00007fff8007ac24 0000000044000484 0000000000004000 00007fff801405e8
  GPR08: 900000000280f033 0000000024000484 0000000000000000 0000000000000030
  GPR12: 9000000000001003 00007fff801bc370 0000000000000000 0000000000000000
  GPR16: 0000000000000000 0000000000000000 0000000000000000 0000000000000000
  GPR20: 0000000000000000 0000000000000000 0000000000000000 0000000000000000
  GPR24: 0000000000000000 0000000000000000 0000000000000000 0000000000000000
  GPR28: 00007fff801b0000 0000000000000000 00000000217707a0 00007fffce481918
  NIP [ffff000000000000] 0xffff000000000000
  LR [00000000217706a4] 0x217706a4
  Call Trace:
  Instruction dump:
  XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX
  XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX

Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Reviewed-by: Mahesh Salgaonkar <mahesh@linux.vnet.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
2017-08-31 14:26:04 +10:00
..
boot Merge branch 'fixes' into next 2017-08-23 22:20:10 +10:00
configs powerpc/configs/6xx: Drop removed CONFIG_USB_LED 2017-08-28 22:10:25 +10:00
crypto Merge branch 'linus' of git://git.kernel.org/pub/scm/linux/kernel/git/herbert/crypto-2.6 2017-05-02 15:53:46 -07:00
include powerpc/powernv: Use kernel crash path for machine checks 2017-08-31 14:26:04 +10:00
kernel powerpc/powernv: Use kernel crash path for machine checks 2017-08-31 14:26:04 +10:00
kvm Merge branch 'topic/ppc-kvm' into next 2017-08-29 21:26:30 +10:00
lib powerpc/string: Implement optimized memset variants 2017-08-17 23:04:35 +10:00
math-emu Replace <asm/uaccess.h> with <linux/uaccess.h> globally 2016-12-24 11:46:01 -08:00
mm powerpc/mm: Make switch_mm_irqs_off() out of line 2017-08-23 22:48:51 +10:00
net powerpc/bpf: Use memset32() to pre-fill traps in BPF page(s) 2017-08-17 23:04:47 +10:00
oprofile ktime: Cleanup ktime_set() usage 2016-12-25 17:21:22 +01:00
perf Merge branch 'topic/ppc-kvm' into next 2017-08-17 23:14:17 +10:00
platforms powerpc/powernv: Use kernel crash path for machine checks 2017-08-31 14:26:04 +10:00
purgatory powerpc: Fix invalid use of register expressions 2017-08-10 22:29:41 +10:00
sysdev powerpc/xive: Fix the size of the cpumask used in xive_find_target_in_mask() 2017-08-24 15:20:18 +10:00
tools powerpc/64: Tool to check head sections location sanity 2017-05-30 14:59:51 +10:00
xmon powerpc/xmon: Exclude all of xmon from ftrace 2017-08-15 15:30:17 +10:00
Kconfig powerpc/mm: Implement STRICT_KERNEL_RWX on PPC32 2017-08-15 22:55:57 +10:00
Kconfig.debug powerpc/xmon: Enable disassembly files (compilation changes) 2017-02-15 20:02:42 +11:00
Makefile Merge branch 'fixes' into next 2017-08-23 22:20:10 +10:00
Makefile.postlink powerpc/64: Tool to check head sections location sanity 2017-05-30 14:59:51 +10:00