On 25/02/2017 04:44, Ross Zwisler wrote: > During Crystal Ridge testing in KVM virtual machines we have occasionally seen > "suspicious RCU usage" messages. They don't seem to be tied to any one > specific test, and my guess is that we are occasionally just losing a race. I think it's just a trivial ordering bug: diff --git a/arch/x86/kernel/kvm.c b/arch/x86/kernel/kvm.c index 14f65a5f938e..5215629ad692 100644 --- a/arch/x86/kernel/kvm.c +++ b/arch/x86/kernel/kvm.c @@ -161,8 +161,8 @@ void kvm_async_pf_task_wait(u32 token) */ rcu_irq_exit(); native_safe_halt(); - rcu_irq_enter(); local_irq_disable(); + rcu_irq_enter(); } } if (!n.halted) because the async page fault code checks for preempt_disable() already, and kmap_atomic already does preempt_disable outside pagefault_disable. Let me know if the above is enough to fix it for you. Paolo
