linux-kernel - Re: [PATCH v3 1/7] KVM: MMU: fix release noslot pfn

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Date:	Mon, 24 Sep 2012 13:24:16 +0200
From:	Gleb Natapov <gleb@...hat.com>
To:	Xiao Guangrong <xiaoguangrong@...ux.vnet.ibm.com>
Cc:	Avi Kivity <avi@...hat.com>, Marcelo Tosatti <mtosatti@...hat.com>,
	LKML <linux-kernel@...r.kernel.org>, KVM <kvm@...r.kernel.org>
Subject: Re: [PATCH v3 1/7] KVM: MMU: fix release noslot pfn

On Mon, Sep 24, 2012 at 12:59:32PM +0800, Xiao Guangrong wrote:
> On 09/23/2012 05:13 PM, Gleb Natapov wrote:
> > On Fri, Sep 21, 2012 at 02:57:19PM +0800, Xiao Guangrong wrote:
> >> We can not directly call kvm_release_pfn_clean to release the pfn
> >> since we can meet noslot pfn which is used to cache mmio info into
> >> spte
> >>
> > Wouldn't it be better to move the check into kvm_release_pfn_clean()?
> 
> I think there is no reason for us to prefer to adding this branch in
> the common code. :)

Is the function performance critical? Is function called without the check
on a hot path?  The function already contains much heavier kvm_is_mmio_pfn()
check. If most/all function invocation require check before call it's
better to move it inside.
 
--
			Gleb.
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