linux-kernel - Re: [PATCH] KVM: don't sent IPI if the vcpu is not online

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Date:	Mon, 06 Sep 2010 08:46:07 +0300
From:	Avi Kivity <avi@...hat.com>
To:	Xiao Guangrong <xiaoguangrong@...fujitsu.com>
CC:	Marcelo Tosatti <mtosatti@...hat.com>,
	LKML <linux-kernel@...r.kernel.org>, KVM <kvm@...r.kernel.org>,
	Alexander Graf <agraf@...e.de>
Subject: Re: [PATCH] KVM: don't sent IPI if the vcpu is not online

  On 09/06/2010 04:48 AM, Xiao Guangrong wrote:
> On 09/05/2010 03:18 PM, Avi Kivity wrote:
>>   On 09/03/2010 07:12 AM, Xiao Guangrong wrote:
>>> It's no need sent IPI to the vcpu which is schedule out
>>>
>>>
>>> @@ -86,6 +86,7 @@ struct kvm_vcpu {
>>>        unsigned long requests;
>>>        unsigned long guest_debug;
>>>        int srcu_idx;
>>> +    bool online;
>> Why not check for guest_mode instead?
>>
> Oh, i forget it...but 'vcpu->guest_mode' is only used in x86 platform,
> and make_all_cpus_request() is a common function.

We can have a function kvm_vcpu_guest_mode() that is defined differently 
for x86 and the other.

> So, maybe it's better use 'vcpu->online' here, and move 'guest_mode' into
> 'vcpu->arch' ?

I think guest_mode makes sense for the other archs for reducing IPIs, so 
let's leave it common and recommend that they implement it.  Alex, if 
you're ever bored.

-- 
I have a truly marvellous patch that fixes the bug which this
signature is too narrow to contain.

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