[Qemu-devel] [Bug 1636217] Re: qemu-kvm 2.7 does not boot kvm VMs with virtio on top of VMware ESX

[Mykola Ivanets <1636217@bugs.launchpad.net>]

Well, it appeared that it is not enough to set "disable-modern=on" for
virtio-blk-pci devices. You have to do the same for virtio-scsi-pci, and
may be for other virtio devices you are using to disable virtio 1.0. But
VM will hangs latter on during boot process if you use virtio-rng-pci.

"-machine accel=tcg" will work but in cost of performance penalty due to
software virtualization.

So I found "-machine type=pc-i440fx-x" where x <= 2.6 the only reliable
workaround.

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https://bugs.launchpad.net/bugs/1636217

Title:
  qemu-kvm 2.7 does not boot kvm VMs with virtio on top of VMware ESX

Status in QEMU:
  New

Bug description:
  After todays Proxmox update all my Linux VMs stopped booting.

  # How to reproduce
  - Have KVM on top of VMware ESX (I use VMware ESX 6)
  - Boot Linux VM with virtio Disk drive.

  
  # Result
  virtio based VMs do not boot anymore:

  root@demotuxdc:/etc/pve/nodes/demotuxdc/qemu-server# grep virtio0 100.conf 
  bootdisk: virtio0
  virtio0: pvestorage:100/vm-100-disk-1.raw,discard=on,size=20G

  (initially with cache=writethrough, but that doesn´t matter)

  What happens instead is:

  - BIOS displays "Booting from harddisk..."
  - kvm process of VM loops at about 140% of Intel(R) Core(TM) i5-6260U CPU @ 1.80GHz Skylake dual core CPU

  Disk of course has valid bootsector:

  root@demotuxdc:/srv/pvestorage/images/100# file -sk vm-100-disk-1.raw 
  vm-100-disk-1.raw: DOS/MBR boot sector DOS/MBR boot sector DOS executable (COM), boot code
  root@demotuxdc:/srv/pvestorage/images/100# head -c 2048 vm-100-disk-1.raw | hd | grep GRUB
  00000170  be 94 7d e8 2e 00 cd 18  eb fe 47 52 55 42 20 00  |..}.......GRUB .|

  
  # Workaround 1
  - Change disk from virtio0 to scsi0
  - Debian boots out of the box after this change
  - SLES 12 needs a rebuilt initrd
  - CentOS 7 too, but it seems that is not even enough and it still fails (even in hostonly="no" mode for dracut)

  
  # Workaround 2
  Downgrade pve-qemu-kvm 2.7.0-3 to 2.6.2-2.

  
  # Expected results
  Disk boots just fine via virtio like it did before.

  
  # Downstream bug report
  Downstream suggests an issue with upstream qemu-kvm:

  https://bugzilla.proxmox.com/show_bug.cgi?id=1181

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