linux-kernel - Re: [RESEND 2][PATCH 4/4] Modify KVM to update guest time accounting.

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Date:	Mon, 15 Oct 2007 12:53:36 +0200
From:	Laurent Vivier <Laurent.Vivier@...l.net>
To:	Avi Kivity <avi@...ranet.com>
Cc:	Ingo Molnar <mingo@...e.hu>,
	linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [RESEND 2][PATCH 4/4] Modify KVM to update guest time	accounting.

Avi Kivity wrote:
> Ingo Molnar wrote:
>> * Avi Kivity <avi@...ranet.com> wrote:
>>
>>  
>>> This bit can go; for the external module I can add it back in
>>> external-module-compat.h.  No need to pollute mainline with backward
>>> compatibility stuff.
>>>     
>>
>> hm:
>>
>> static inline void kvm_guest_enter(void)
>> {
>>         current->flags |= PF_VCPU;
>> }
>>
>> static inline void kvm_guest_exit(void)
>> {
>> }
>>
>> shouldnt PF_VCPU be cleared in kvm_guest_exit()?
>>   
> 
> IIRC the accounting code clears it, but yes, it may not have been called
> at all, so clearing it here is needed.
> 

No, It must not be cleared here because we can't enter in the accounting code
between kvm_guest_enter(void) and kvm_guest_exit(void).

This is why the accounting code clears it.

I put a kvm_guest_exit() only for symmetry.

Laurent
-- 
---------------- Laurent.Vivier@...l.net  -----------------
"Given enough eyeballs, all bugs are shallow" E. S. Raymond


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