[Bug 1856834] Re: Virtio broken in qemu ppc in 4.2.0 and other versions

[ecsdn]

fyi from what I recall guest kernel was built using mpc85xx_defconfig
with some additions like virtio etc. If virtio is working for you just
fine using same command as mine, then perhaps its some peculiarity to do
with my specific guest kernel or kernel version? (uImage is about 3.4M
with equivalent vmlinux about 72M)

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https://bugs.launchpad.net/bugs/1856834

Title:
  Virtio broken in qemu ppc in 4.2.0 and other versions

Status in QEMU:
  New

Bug description:
  The same qemu -M mpc... command that works on qemu-system-ppc version
  2.8.0 freezes guest on bootup and shows error for qemu-system-ppc
  version 4.2.0release and 4.19dirtygit:

  qemu-system-ppc: virtio-blk failed to set guest notifier (-24), ensure -accel 
kvm is set.
  qemu-system-ppc: virtio_bus_start_ioeventfd: failed. Fallback to userspace 
(slower).

  ends/freezes at:
  nbd: registered device at major 43
   vda:

  I'm using -drive file=/home/me/rawimage.dd,if=virtio and works fine in
  version 2.8.0 installed with apt-get install (Ubuntu 17.04) and also
  with 2.8.0 official release from git/github that I compiled/built
  myself. But both of the newer releases fail on the same exact machine
  same config.

  I also noticed that qemu-2.8.0 was fine with mtd but the newer ones I tried 
weren't, ie gave
  qemu-system-ppc: -drive if=mtd: machine type does not support 
if=mtd,bus=0,unit=0
  (but I removed -drive if=mtd since wasn't using it anyway)

  I also tried on windows but I think virtio doesn't work on windows
  hosts at all? On windows host it fails the same way, even version 2.12
  as well as 4.1.10...

  used:
  ./configure --prefix=/opt/... --enable-fdt --enable-kvm --enable-debug

  (basically all steps the same on same exact system same config, yet
  2.8.0 works fine whether apt-get installed or built from source while
  the others I built, 4.19/4.2.0 or 2.12/4.1.10(win) don't.)

  In case newer qemu versions act weird on various kernels, I did try with both 
vmlinuz-4.10.0-19-generic and vmlinuz-4.13.12-041312-generic (I didn't compile 
them but I can provide config-..files. This is on Ubuntu 17.04 x86_64 host 
emulating e500v2 cpm guest, ie -M mpc... GUEST kernel 2.6.32.44 which is why I 
can't use -M ppce500 instead..)
  tx
       ecs

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