From: Wanpeng Li <wanpeng.li@xxxxxxxxxxx> Commit 9b132fbe5419 (Add rcu user eqs exception hooks for async page fault) adds rcu_irq_enter/exit() to kvm_async_pf_task_wait() to exit cpu idle eqs when needed, to protect the code that needs use rcu. There is no need to call this pairs if async page fault is not triggered from idle task. This patch invokes rcu irq exit if it is not triggered from idle task. Cc: Paolo Bonzini <pbonzini@xxxxxxxxxx> Cc: Radim Krčmář <rkrcmar@xxxxxxxxxx> Signed-off-by: Wanpeng Li <wanpeng.li@xxxxxxxxxxx> --- v1 -> v2: * update patch description arch/x86/kernel/kvm.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) diff --git a/arch/x86/kernel/kvm.c b/arch/x86/kernel/kvm.c index 43e10d6..e70ed72 100644 --- a/arch/x86/kernel/kvm.c +++ b/arch/x86/kernel/kvm.c @@ -141,6 +141,8 @@ void kvm_async_pf_task_wait(u32 token) n.token = token; n.cpu = smp_processor_id(); n.halted = is_idle_task(current) || preempt_count() > 1; + if (!n.halted) + rcu_irq_exit(); init_swait_queue_head(&n.wq); hlist_add_head(&n.link, &b->list); raw_spin_unlock(&b->lock); @@ -167,8 +169,9 @@ void kvm_async_pf_task_wait(u32 token) } if (!n.halted) finish_swait(&n.wq, &wait); + else + rcu_irq_exit(); - rcu_irq_exit(); return; } EXPORT_SYMBOL_GPL(kvm_async_pf_task_wait); -- 2.7.4
