[Qemu-devel] [Bug 1780928] Re: v2.12.0-2321-gb34181056c: vcpu hotplug crashes qemu-kvm with segfault

[Greg Kurz]

The parent class (ie, TYPE_ICP) doesn't implement DeviceClass::reset().
It directly registers a reset handler with qemu_register_reset()
instead. This is needed for cold plugged ICPs to be reset during machine
reset since they're not SysBus devices.

Cedric's patch missed that, but rather than reverting it, I'd rather go forward 
and:
- introduce an abstract TYPE_ICP_BASE class that implements DeviceClass::reset()
- have the current TYPE_ICP and all other specialized ICP types to derive from 
TYPE_ICP_BASE
- have all specialized ICP types to register reset handlers with 
qemu_register_reset()

This would match what was recently done with the ICS types.

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https://bugs.launchpad.net/bugs/1780928

Title:
  v2.12.0-2321-gb34181056c: vcpu hotplug crashes qemu-kvm with segfault

Status in QEMU:
  Confirmed

Bug description:
  vcpu hotplug crashes upstream qemu(v2.12.0-2321-gb34181056c), vcpu
  hotplug works fine in v2.12.0-rc4.

  Host: Power8, kernel: 4.18.0-rc2-00037-g6f0d349d922b
  Guest: Power8, kernel: 4.18.0-rc3-00183-gc42c12a90545 (base image: fedora27 
ppc64le)

  /usr/share/avocado-plugins-vt/build/qemu/ppc64-softmmu/qemu-system-ppc64 -M 
pseries,accel=kvm,max-cpu-compat=power8 -m 8192 -device 
virtio-scsi-pci,id=scsi0,bus=pci.0,addr=0x2 -drive 
file=/var/lib/avocado/data/avocado-vt/images/jeos-27-ppc64le.qcow2,format=qcow2,if=none,id=drive1
 -device scsi-hd,drive=drive1,bus=scsi0.0 -smp 
1,cores=1,threads=1,sockets=1,maxcpus=8 -serial /dev/pts/0 -monitor stdio -vga 
none -nographic -kernel /home/kvmci/linux/vmlinux -append 'root=/dev/sda2 rw 
console=tty0 console=ttyS0,115200 init=/sbin/init initcall_debug' -nic 
user,model=virtio-net-pci 
  QEMU 2.12.50 monitor - type 'help' for more information
  (qemu) device_add host-spapr-cpu-core,id=core1,core-id=1
  Segmentation fault (core dumped)

  
  Guest initial cpu:
  # lscpu
  Architecture:        ppc64le
  Byte Order:          Little Endian
  CPU(s):              1
  On-line CPU(s) list: 0
  Thread(s) per core:  1
  Core(s) per socket:  1
  Socket(s):           1
  NUMA node(s):        1
  Model:               2.1 (pvr 004b 0201)
  Model name:          POWER8 (architected), altivec supported
  Hypervisor vendor:   KVM
  Virtualization type: para
  L1d cache:           64K
  L1i cache:           32K
  NUMA node0 CPU(s):   0

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