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Date: Mon, 09 Jul 2007 09:41:38 +0300
From: Avi Kivity <avi@qumranet.com>
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To: Andi Kleen <andi@firstfloor.org>
CC: linux-kernel@vger.kernel.org, KVM <kvm-devel@lists.sourceforge.net>
Subject: Re: [PATCH][RFC] kvm-scheduler integration
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Andi Kleen wrote:
> Avi Kivity <avi-atKUWr5tajBWk0Htik3J/w@public.gmane.org> writes:
>   
>> diff --git a/include/linux/sched.h b/include/linux/sched.h
>> index 693f0e6..b705876 100644
>> --- a/include/linux/sched.h
>> +++ b/include/linux/sched.h
>> @@ -875,6 +875,10 @@ struct task_struct {
>>  	pid_t pid;
>>  	pid_t tgid;
>>  
>> +#ifdef CONFIG_SCHED_KVM
>> +	struct kvm_vcpu *kvm_vcpu;
>> +#endif
>>     
>
> You should be careful to put this into a cache line that 
> is already touched during context switch. Otherwise
> if it needs an additional cache miss it might become
> very costly
>   

Yeah, I'll look into task_struct again to find a good place.

> Also it's a bit worrying to expose hooks into the scheduler
> to any modules. How would others be stopped from abusing this?
>   

The functions for installing a hook are out-of-line and
EXPORT_SYMBOL_GPL'ed, in case that helps.

-- 
Do not meddle in the internals of kernels, for they are subtle and quick to panic.