On 18/02/2016 17:27, Radim Krčmář wrote: > 2016-02-18 16:53+0100, Paolo Bonzini: >> Patch 9 is okay, but it is also necessary to clear IsRunning in >> kvm_arch_vcpu_blocking and set it in kvm_arch_vcpu_unblocking. In >> addition, vcpu_put/vcpu_load should not modify IsRunning between >> kvm_arch_vcpu_blocking and kvm_arch_vcpu_unblocking. Do you agree? > > Yes. > > I think we don't need to clear IsRunning on preemption, which would > simplify the protection. (I haven't thought much about userspace exit, > so maybe we could skip that one as well, but we don't need to now.) > > The reason for that is that KVM knows that the VCPU was scheduled out, > so it couldn't do much in the AVIC VMEXIT. > (KVM could force scheduler to pritioritize the VCPU, but our kick > doesn't do that now and it seems like a bad idea.) > > Does it seem reasonable?
Yes, and in fact it wouldn't need to clear and set IsRunning on vcpu_put/vcpu_load; only on vcpu_blocking/vcpu_unblocking. The IsRunning flag is more of a IsNotHalted flag, in the end. Paolo
