> Applied with a rewritten commit message: > > KVM: don't check for PF_VCPU when yielding > > kvm_enter_guest() has to be called with preemption disabled and will > set PF_VCPU. Current code takes PF_VCPU as a hint that the VCPU thread > is running and therefore needs no yield. > > However, the check on PF_VCPU is wrong on s390, where preemption > has to stay enabled on s390 in order to correctly process page faults. > Thus, s390 reenables preemption and starts to execute the guest. > The thread might be scheduled out between kvm_enter_guest() and > kvm_exit_guest(), resulting in PF_VCPU being set but not being run. > When this happens, the opportunity for directed yield is missed. > > However, this check is done already in kvm_vcpu_on_spin before calling > kvm_vcpu_yield_loop: > > if (!ACCESS_ONCE(vcpu->preempted)) > continue; > > so the check on PF_VCPU is superfluous in general, and this patch > removes it. > > Signed-off-by: David Hildenbrand <dahi@xxxxxxxxxxxxxxxxxx> > Signed-off-by: Paolo Bonzini <pbonzini@xxxxxxxxxx> > Perfect, thanks! David -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
