linux-kernel - Re: kvm: RCU warning in async pf

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Date:	Sat, 14 Apr 2012 11:44:53 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Gleb Natapov <gleb@...hat.com>
Cc:	Sasha Levin <levinsasha928@...il.com>, Avi Kivity <avi@...hat.com>,
	Marcelo Tosatti <mtosatti@...hat.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...e.hu>,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	kvm <kvm@...r.kernel.org>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	Dave Jones <davej@...hat.com>
Subject: Re: kvm: RCU warning in async pf

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).


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