Am 21.01.24 um 12:17 schrieb Yi Wang:
From: Yi Wang <foxywang@xxxxxxxxxxx> We found that it may cost more than 20 milliseconds very accidentally to enable cap of KVM_CAP_SPLIT_IRQCHIP on a host which has many vms already. The reason is that when vmm(qemu/CloudHypervisor) invokes KVM_CAP_SPLIT_IRQCHIP kvm will call synchronize_srcu_expedited() and might_sleep and kworker of srcu may cost some delay during this period. One way makes sence is setup empty irq routing when creating vm and so that x86/s390 don't need to setup empty/dummy irq routing. Note: I have no s390 machine so the s390 patch has not been tested.
I just did a quick sniff and it still seems to work. No performance check etc.
