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

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Message-ID: <50647E0B.6080303@redhat.com>
Date:	Thu, 27 Sep 2012 18:25:47 +0200
From:	Avi Kivity <avi@...hat.com>
To:	Xiao Guangrong <xiaoguangrong@...ux.vnet.ibm.com>
CC:	Gleb Natapov <gleb@...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 09/24/2012 02:32 PM, Xiao Guangrong wrote:

> 3 places after the whole patchset (There are some cleanups after this patch).
> 
>> and one by even stronger is_error_pfn(). 
> 
> This one is:
> 
> |	if (!is_error_pfn(pfn)) {
> |                kvm_release_pfn_clean(pfn);
> |                return true;
> |	}
> |
> |	return false;
> 
> We can change it to:
> 
> | if (is_error_pfn(pfn))
> |	return false;
> |
> | kvm_release_pfn_clean(pfn);
> | return true;
> 
>> I guess when/if other architectures will add MMIO MMU
>> caching they will need to guard kvm_release_pfn_clean() by is_noslot_pfn()
>> too in most cases. I am not insisting, but as this patch shows it is
>> easy to miss the check before calling the function.
> 
> Sounds reasonable. I will consider it if Avi/Marcelo have no object on
> it.

I think it's a good idea.

Looks like we traded the unscalable error pages for these branches, I
think it's a reasonable tradeoff.

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