Re: [PATCH/RFC] KVM: track pid for VCPU only on KVM_RUN ioctl

Christian Borntraeger
2014-08-19T09:47:41Z

On 19/08/14 11:27, Paolo Bonzini wrote:
> Il 19/08/2014 10:38, Christian Borntraeger ha scritto:
>>>> The patch may be okay, but I'm worried that it might be hiding a bug in
>>>> QEMU.
>> On s390 we call "KVM_S390_INITIAL_RESET" from several reset functions, e.g. during
>> CPU creation. This is the first hickup and the pid now points to the main thread.
>
> Any reason to have a special ioctl instead of SET_REGS/SET_ONE_REG/...
> (via kvm_cpu_synchronize_state, which does the ioctls in the VCPU thread)?

Historical reasons mostly. Older kernel miss several interfaces to bring the CPU in a defined state (pending interrupts, cpu state, some registers...)

Good news is that we are working on getting rid of it: cpu states are now available as far as I can see, only local interrupt flushing is missing.This needs some more work on our side. So in some month we probably will have a QEMU version that does not need to call this any more. For todays QEMU this patch help though.

Christian