He, Qing wrote: > Hi folks, > I found that Windows guests often fail reboots in current > kvm.git. Either the guest hangs, or it reports double fault exception > which causes qemu aborts. This is not shown with -no-kvm-irqchip option. > > After some investigation, it seems that this is caused by lack > of in-kernel components reset. Several windows guests will write RESET > command to 8042, the keyboard controller. On receiving the command, qemu > device model will call qemu_system_reset() to reset everything to the > initial state. However, this mechanism is broken when in-kernel > components is introduced: qemu doesn't communicate the reset request to > kvm, so kvm uses stale device state on the next booting, which fails > reboot. > > To resolve this, there are at least two options: > 1. modify qemu_system_reset(), so that qemu destroys kvm context > and re-creates. > 2. introduce a new ioctl, say KVM_RESET, to kvm. On receiving > this ioctl, the kernel calls reset handlers registered by other > components (vcpu, lapic, pic, ioapic, pit, etc.), either against vm or > against each vcpu. > > IMO, the first one is easier in modification and maintaining, > but the second one is closer to qemu logics. Which do you think is more > appropriate? > > Any comment? > > Thanks, > Qing > I'm voting for option 2. As you said its closer to qemu's device model approach and it's also similar to kernel components (*pi*) save/restore methods. It also minimized qemu changes. Dor.
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