From c5e015d4949aa665c486cae6884beb00b97e3dea Mon Sep 17 00:00:00 2001 From: Sasha Levin Date: Fri, 19 Oct 2012 12:11:55 -0400 Subject: [PATCH] KVM guest: exit idleness when handling KVM_PV_REASON_PAGE_NOT_PRESENT KVM_PV_REASON_PAGE_NOT_PRESENT kicks cpu out of idleness, but we haven't marked that spot as an exit from idleness. Not doing so can cause RCU warnings such as: [ 732.788386] =============================== [ 732.789803] [ INFO: suspicious RCU usage. ] [ 732.790032] 3.7.0-rc1-next-20121019-sasha-00002-g6d8d02d-dirty #63 Tainted: G W [ 732.790032] ------------------------------- [ 732.790032] include/linux/rcupdate.h:738 rcu_read_lock() used illegally while idle! [ 732.790032] [ 732.790032] other info that might help us debug this: [ 732.790032] [ 732.790032] [ 732.790032] RCU used illegally from idle CPU! [ 732.790032] rcu_scheduler_active = 1, debug_locks = 1 [ 732.790032] RCU used illegally from extended quiescent state! [ 732.790032] 2 locks held by trinity-child31/8252: [ 732.790032] #0: (&rq->lock){-.-.-.}, at: [] __schedule+0x178/0x8f0 [ 732.790032] #1: (rcu_read_lock){.+.+..}, at: [] cpuacct_charge+0xe/0x200 [ 732.790032] [ 732.790032] stack backtrace: [ 732.790032] Pid: 8252, comm: trinity-child31 Tainted: G W 3.7.0-rc1-next-20121019-sasha-00002-g6d8d02d-dirty #63 [ 732.790032] Call Trace: [ 732.790032] [] lockdep_rcu_suspicious+0x10b/0x120 [ 732.790032] [] cpuacct_charge+0x90/0x200 [ 732.790032] [] ? cpuacct_charge+0xe/0x200 [ 732.790032] [] update_curr+0x1a3/0x270 [ 732.790032] [] dequeue_entity+0x2a/0x210 [ 732.790032] [] dequeue_task_fair+0x45/0x130 [ 732.790032] [] dequeue_task+0x89/0xa0 [ 732.790032] [] deactivate_task+0x1e/0x20 [ 732.790032] [] __schedule+0x879/0x8f0 [ 732.790032] [] ? trace_hardirqs_off+0xd/0x10 [ 732.790032] [] ? kvm_async_pf_task_wait+0x1d5/0x2b0 [ 732.790032] [] schedule+0x55/0x60 [ 732.790032] [] kvm_async_pf_task_wait+0x1f4/0x2b0 [ 732.790032] [] ? abort_exclusive_wait+0xb0/0xb0 [ 732.790032] [] ? prepare_to_wait+0x25/0x90 [ 732.790032] [] do_async_page_fault+0x56/0xa0 [ 732.790032] [] async_page_fault+0x28/0x30 Signed-off-by: Sasha Levin Acked-by: Gleb Natapov Acked-by: Paul E. McKenney Signed-off-by: Avi Kivity --- arch/x86/kernel/kvm.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/arch/x86/kernel/kvm.c b/arch/x86/kernel/kvm.c index b3e5e51bc907..4180a874c764 100644 --- a/arch/x86/kernel/kvm.c +++ b/arch/x86/kernel/kvm.c @@ -247,7 +247,10 @@ do_async_page_fault(struct pt_regs *regs, unsigned long error_code) break; case KVM_PV_REASON_PAGE_NOT_PRESENT: /* page is swapped out by the host. */ + rcu_irq_enter(); + exit_idle(); kvm_async_pf_task_wait((u32)read_cr2()); + rcu_irq_exit(); break; case KVM_PV_REASON_PAGE_READY: rcu_irq_enter();