#250 in-kernel PIT blocks DragonFlyBSD from booting

[Carlo Marcelo Arenas Belon]

starting with kvm 64, DragonFlyBSD guests won't be able to boot unless -no-kvm-pit or -no-kvm-irqchip is used (-no-kvm works as well) :

cpu model: Intel(R) Core(TM)2 CPU

kvm version: kvm 66 (kvm>=64 fails, kvm<=63 works)
host kernel: 2.6.24-gentoo-r4 (SMP)
host arch: x86_64

to replicate, download dragonfly ISO (it is a livecd) and boot from it :

kvm -curses -cdrom dfly-1.12.2_REL.iso -boot d

[Marcelo Tosatti]

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DragonFlyBSD uses mode 4 of the PIT which the in-kernel emulation
simply ignores.

Mode 4 seems to be similar to one-shot mode, other than the fact
that mode 4 starts counting after the next CLK pulse once programmed,
and mode1 starts counting immediately, so this should be OK:

http://people.redhat.com/~mtosatti/kvm-i8254-mode4.patch

[Carlo Marcelo Arenas Belon]

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working stable with the patch