Il 26/11/2013 13:40, Zhanghaoyu (A) ha scritto: > When guest set irq smp_affinity, VMEXIT occurs, then the vcpu thread will > IOCTL return to QEMU from hypervisor, then vcpu thread ask the hypervisor to > update the irq routing table, > in kvm_set_irq_routing, synchronize_rcu is called, current vcpu thread is > blocked for so much time to wait RCU grace period, and during this period, > this vcpu cannot provide service to VM, > so those interrupts delivered to this vcpu cannot be handled in time, and the > apps running on this vcpu cannot be serviced too. > It's unacceptable in some real-time scenario, e.g. telecom. > > So, I want to create a single workqueue for each VM, to asynchronously > performing the RCU synchronization for irq routing table, > and let the vcpu thread return and VMENTRY to service VM immediately, no more > need to blocked to wait RCU grace period. > And, I have implemented a raw patch, took a test in our telecom environment, > above problem disappeared.
I don't think a workqueue is even needed. You just need to use call_rcu to free "old" after releasing kvm->irq_lock. What do you think? Paolo
