No kernel interface to reset a VCPU

[Jan Kiszka <jan.kiszka@siemens.com>]

Hi all,

looks to me like there is no way to properly reset the boot processor.
The current pattern used by qemu[-kvm] is to reload all registers with
their reset values. But that does not affect the internal VCPU states
the KVM keeps in the kernel. They are only reset during VCPU setup or
after receiving a SIPI (and the latter only helps with secondary CPUs).

So the only way around it with the current kernel interface is to
destroy/recreate the BSP on reset, right? /me is looking into such an
approach now.


We stumbled over inconsistent VCPU states with our internal qemu-kvm
tree. We have a legacy watchdog emulation here that triggered but failed
to bring up the system again. I wasn't able to create a similar case
with a standard environment yet, but I think it is not unrealistic for
qemu-kvm as well. Hacking kvm_arch_vcpu_reset() into KVM that triggers
on the right register values "solved" the issue here.

Jan

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