On 12/22/22 21:30, Michal Luczaj wrote:
+ idx = srcu_read_lock(&kvm->srcu); + mutex_lock(&kvm->lock); evtchnfd = idr_find(&kvm->arch.xen.evtchn_ports, port); mutex_unlock(&kvm->lock);
This lock/unlock pair can cause a deadlock because it's inside the SRCU read side critical section. Fortunately it's simpler to just use mutex_lock for the whole function instead of using two small critical sections, and then SRCU is not needed.
However, the same issue exists in kvm_xen_hcall_evtchn_send where idr_find is not protected by kvm->lock. In that case, it is important to use rcu_read_lock/unlock() around it, because idr_remove() will *not* use synchronize_srcu() to wait for readers to complete.
Paolo
