From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751526AbdFGMEZ (ORCPT ); Wed, 7 Jun 2017 08:04:25 -0400 Received: from mail-pg0-f67.google.com ([74.125.83.67]:33016 "EHLO mail-pg0-f67.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751413AbdFGMEY (ORCPT ); Wed, 7 Jun 2017 08:04:24 -0400 From: Wanpeng Li X-Google-Original-From: Wanpeng Li To: linux-kernel@vger.kernel.org, kvm@vger.kernel.org Cc: Paolo Bonzini , =?UTF-8?q?Radim=20Kr=C4=8Dm=C3=A1=C5=99?= , Wanpeng Li Subject: [PATCH] KVM: async_pf: Fix rcu_irq_enter/exit() usage Date: Wed, 7 Jun 2017 05:04:00 -0700 Message-Id: <1496837040-8200-1-git-send-email-wanpeng.li@hotmail.com> X-Mailer: git-send-email 2.7.4 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Wanpeng Li 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 fixes it by rcu irq exit if it is not triggered from idle task to avoid rcu hang after schedule() in the for loop. Cc: Paolo Bonzini Cc: Radim Krčmář Signed-off-by: Wanpeng Li --- 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