** Also affects: ubuntu-z-systems
   Importance: Undecided
       Status: New

** Changed in: ubuntu-z-systems
   Importance: Undecided => High

** Changed in: ubuntu-z-systems
     Assignee: (unassigned) => Canonical Kernel Team (canonical-kernel-team)

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  kvm default ubuntu kernel: Kernel panic - not syncing: Fatal
  exception: panic_on_oops

Status in Ubuntu on IBM z Systems:
Status in linux package in Ubuntu:

Bug description:
  During guest/isolated container execution following kernel bug got

  [  249.792522] Modules linked in: bridge stp llc binfmt_misc qeth_l2 chsc_sch 
eadm_sch tape_3590 tape tape_class qeth ccwgroup dm_round_robin ib_iser rdma_cm 
iw_cm ib_cm ib_sa ib_mad ib_core ib_addr iscsi_tcp libiscsi_tcp libiscsi 
scsi_transport_iscsi dm_multipath btrfs zlib_deflate raid10 raid456 
async_memcpy async_raid6_recov async_pq async_xor async_tx xor raid6_pq 
libcrc32c raid1 linear raid0 ghash_s390 prng aes_s390 des_s390 des_generic 
sha512_s390 sha256_s390 sha1_s390 sha_common dasd_eckd_mod dasd_mod zfcp qdio 
  [  249.792558] CPU: 1 PID: 2461 Comm: qemu-system-s39 Not tainted 
4.4.0-42-generic #62-Ubuntu
  [  249.792560] task: 00000000edf44c90 ti: 000000007be68000 task.ti: 
  [  249.792562] User PSW : 0705200180000000 000003ff9e683730
  [  249.792564]            R:0 T:1 IO:1 EX:1 Key:0 M:1 W:0 P:1 AS:0 CC:2 PM:0 
                 User GPRS: fffffffffffff000 0000000000000001 0000000000000001 
  [  249.792566]            000003ff9e789420 00000000ffffffff 0000000000000948 
  [  249.792568]            0000000000000000 0000000000000948 0000000000000000 
  [  249.792569]            000003ff9e789000 0000000000000000 000003ff9e6845e6 
  [  249.792577] User Code: 000003ff9e683720: ec32000100d9    aghik   %r3,%r2,1
                            000003ff9e683726: b9040012        lgr %r1,%r2
                           #000003ff9e68372a: c04000082e7b    larl    
                           >000003ff9e683730: eb1340000030    csg %r1,%r3,0(%r4)
                            000003ff9e683736: ec1200288064    cgrj    
                            000003ff9e68373c: c42800082e72    lgrl    
                            000003ff9e683742: c418000842af    lgrl    
                            000003ff9e683748: a7f4ff09        brc 15,3ff9e68355a
  [  249.792602] Last Breaking-Event-Address:
  [  249.792604]  [<000003ff9e68355e>] 0x3ff9e68355e
  [  249.792605]  
  [  249.792606] Kernel panic - not syncing: Fatal exception: panic_on_oops


  #=== Steps to Reproduce ====================================
  1. Use the KVM kernel module with qemu

  By applying following upstream patch this bug was not triggered again:

  commit f045402984404ddc11016358411e445192919047
  Author: David Hildenbrand <d...@linux.vnet.ibm.com>
  Date:   Thu Jul 7 10:44:10 2016 +0200

      s390/mm: fix gmap tlb flush issues

      __tlb_flush_asce() should never be used if multiple asce belong to
  a mm.

      As this function changes mm logic determining if local or global tlb
      flushes will be neded, we might end up flushing only the gmap asce on all
      CPUs and a follow up mm asce flushes will only flush on the local CPU,
      although that asce ran on multiple CPUs.

      The missing tlb flushes will provoke strange faults in user space and even
      low address protections in user space, crashing the kernel.

      Fixes: 1b948d6caec4 ("s390/mm,tlb: optimize TLB flushing for zEC12")
      Cc: sta...@vger.kernel.org # 3.15+
      Reported-by: Sascha Silbe <si...@linux.vnet.ibm.com>
      Acked-by: Martin Schwidefsky <schwidef...@de.ibm.com>
      Signed-off-by: David Hildenbrand <d...@linux.vnet.ibm.com>
      Signed-off-by: Martin Schwidefsky <schwidef...@de.ibm.com>

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