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Message-ID: <1334396693.2528.45.camel@twins>
Subject: Re: kvm: RCU warning in async pf
From: Peter Zijlstra <peterz@infradead.org>
To: Gleb Natapov <gleb@redhat.com>
Cc: Sasha Levin <levinsasha928@gmail.com>, Avi Kivity <avi@redhat.com>,
        Marcelo Tosatti <mtosatti@redhat.com>,
        Thomas Gleixner <tglx@linutronix.de>, Ingo Molnar <mingo@elte.hu>,
        "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>,
        kvm <kvm@vger.kernel.org>, linux-kernel <linux-kernel@vger.kernel.org>,
        Dave Jones <davej@redhat.com>
Date: Sat, 14 Apr 2012 11:44:53 +0200
In-Reply-To: <20120404123033.GD11918@redhat.com>
References: <1333414472.11455.7.camel@lappy>
	 <20120403105226.GF14939@redhat.com> <20120404123033.GD11918@redhat.com>
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On Wed, 2012-04-04 at 15:30 +0300, Gleb Natapov wrote:
>  
> @@ -253,7 +254,10 @@ do_async_page_fault(struct pt_regs *regs, unsigned long error_code)
>  		kvm_async_pf_task_wait((u32)read_cr2());
>  		break;
>  	case KVM_PV_REASON_PAGE_READY:
> +		rcu_irq_enter();
> +		exit_idle();
>  		kvm_async_pf_task_wake((u32)read_cr2());
> +		rcu_irq_exit();
>  		break;
>  	}
>  }

Wouldn't irq_enter() / irq_exit() be more appropriate? You're basically
taking an interrupt/exception from idle, irq_enter() will fix up
everything that needs fixing up, including time sources (which the
scheduler expects to be up-to-date).