linux-kernel - Re: [PATCH] KVM: x86: Kick VCPU outside PIC lock again

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Date:	Wed, 24 Feb 2010 12:27:59 +0200
From:	Avi Kivity <avi@...hat.com>
To:	Jan Kiszka <jan.kiszka@...mens.com>
CC:	Thomas Gleixner <tglx@...utronix.de>, KVM <kvm@...r.kernel.org>,
	Gleb Natapov <gleb@...hat.com>,
	RT <linux-rt-users@...r.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] KVM: x86: Kick VCPU outside PIC lock again

On 02/24/2010 12:22 PM, Jan Kiszka wrote:
> Avi Kivity wrote:
>    
>> On 02/24/2010 12:13 PM, Jan Kiszka wrote:
>>      
>>>
>>>        
>>>> I see.  Won't we hit the same issue when we call pic functions from
>>>> atomic context during the guest entry sequence?
>>>>
>>>>
>>>>          
>>> If there are such call paths, for sure. What concrete path(s) do you
>>> have in mind?
>>>
>>>
>>>        
>> vcpu_enter_guest() ->  inject_pending_event() ->
>> kvm_cpu_{has,get}_interrupt() ->  various pic functions if you're unlucky.
>>      
> But do they kick anyone or just check/pull information?

Probably not, kicking should be a side effect (or rather the main 
effect) of queueing an interrupt, not dequeuing it.

> Never saw any
> warnings during my tests last year (granted: with older -rt and kvm
> versions).
>    

Well, most guests kill the pic early on.  Will apply the patch.

-- 
error compiling committee.c: too many arguments to function

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