[Bug 1847793] Re: qemu 4.1.0 - Corrupt guest filesystem after new vm install

[Max Reitz]

The bug reported here is not about qcow2 metadata corruption, but about
guest data corruption (qemu-img check reports a clean image).  It’s
entirely possible (and I would even say likely) that there are two
different causes.

We know about two guest data corruptions already (which appeared in
4.1), and both seem to only appear on XFS.  We have fixed one, the other
we don’t quite know yet.

Therefore, I’m wondering whether this is a guest data corruption that we
probably already know about (because it’s on XFS), or whether we don’t
(because it isn’t).

In any case, I would separate these two bug reports on the basis that
this one here is about guest data corruption, whereas 1846427 is about
qcow2 metadata corruption.

Max

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https://bugs.launchpad.net/bugs/1847793

Title:
  qemu 4.1.0 - Corrupt guest filesystem after new vm install

Status in QEMU:
  New

Bug description:
  When I install a new vm with qemu 4.1.0 all the guest filesystems are
  corrupt. The first boot from the install dvd iso is ok and the
  installer work fine. But the guest system hangs after the installer
  finishes and I reboot the guest. I can see the grub boot menue but the
  system cannot load the initramfs.

  Testet with:
  - RedHat Enterprise Linux 7.5, 7.6 and 7.7 (RedHat uses xfs for the /boot and 
/ partition)
  Guided install with the graphical installer, no lvm selected.
  - Debian Stable/Buster (Debian uses ext4 for / and /home partition)
  Guidet install with the graphical installer and default options.

  Used commandline to create the vm disk image:
  qemu-img create -f qcow2 /volumes/disk2-part2/vmdisks/vmtest10-1.qcow2 20G

  Used qemu commandline for vm installation:
  #!/bin/sh
  # vmtest10 Installation
  #
  /usr/bin/qemu-system-x86_64  -cpu SandyBridge-IBRS \
      -soundhw hda \
      -M q35 \
      -k de \
      -vga qxl \
      -machine accel=kvm \
      -m 4096 \
      -display gtk \
      -drive 
file=/volumes/disk2-part2/images/debian-10.0.0-amd64-DVD-1.iso,if=ide,media=cdrom
 \
      -drive 
file=/volumes/disk2-part2/images/vmtest10-1.qcow2,if=virtio,media=disk,cache=writeback
 \
      -boot once=d,menu=off \
      -device virtio-net-pci,mac=52:54:00:2c:02:6c,netdev=vlan0 \
      -netdev bridge,br=br0,id=vlan0 \
      -rtc base=localtime \
      -name "vmtest10" \
      -usb -device usb-tablet \
      -spice disable-ticketing \
      -device virtio-serial-pci \
      -device virtserialport,chardev=spicechannel0,name=com.redhat.spice.0 \
      -chardev spicevmc,id=spicechannel0,name=vdagent $*

  Host OS:
  Archlinux (last updated at 10.10.2019)
  Linux testing 5.3.5-arch1-1-ARCH #1 SMP PREEMPT Mon Oct 7 19:03:08 UTC 2019 
x86_64 GNU/Linux
  No libvirt in use.

  
  With qemu 4.0.0 it works fine without any errors.

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