From: Xiao Guangrong <xiaoguangrong@cn.fujitsu.com>
To: Gleb Natapov <gleb@redhat.com>
Cc: Avi Kivity <avi@redhat.com>,
Marcelo Tosatti <mtosatti@redhat.com>,
LKML <linux-kernel@vger.kernel.org>, KVM <kvm@vger.kernel.org>
Subject: Re: [PATCH v3 2/3] KVM: MMU: fix accessed bit set on prefault path
Date: Wed, 01 Dec 2010 02:15:29 +0800 [thread overview]
Message-ID: <4CF53F41.1040503@cn.fujitsu.com> (raw)
In-Reply-To: <20101130175005.GA2924@redhat.com>
On 12/01/2010 01:50 AM, Gleb Natapov wrote:
> On Wed, Dec 01, 2010 at 12:52:22AM +0800, Xiao Guangrong wrote:
>> On 11/30/2010 09:29 PM, Gleb Natapov wrote:
>>
>>>> + if (!shadow_accessed_mask)
>>>> + return;
>>>> +
>>> I don't get this. As far as I can see VMX inits shadow_accessed_mask to
>>> be zero if ept is enabled. This line here means that we never prefault with ept
>>> enabled. It is opposite from what it should be.
>>>
>>
>> Since it's no accessed bit on EPT, it's no way to distinguish between actually
>> accessed translations and prefault.
> Why is this a problem? We do what this page to not be evicted again
> since we expect it to be accessed.
>
It can't avoid the page to be evicted again since the page is marked accessed only
when spte is droped or updated.
next prev parent reply other threads:[~2010-11-30 18:11 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-11-30 9:34 [PATCH v3 1/3] KVM: MMU: rename 'no_apf' to 'prefault' Xiao Guangrong
2010-11-30 9:36 ` [PATCH v3 2/3] KVM: MMU: fix accessed bit set on prefault path Xiao Guangrong
2010-11-30 13:29 ` Gleb Natapov
2010-11-30 16:52 ` Xiao Guangrong
2010-11-30 17:50 ` Gleb Natapov
2010-11-30 18:15 ` Xiao Guangrong [this message]
2010-11-30 18:38 ` Gleb Natapov
2010-11-30 19:11 ` Xiao Guangrong
2010-11-30 19:20 ` Gleb Natapov
2010-12-01 2:20 ` Xiao Guangrong
2010-12-01 20:42 ` Marcelo Tosatti
2010-11-30 9:37 ` [PATCH v3 3/3] KVM: MMU: retry #PF for softmmu Xiao Guangrong
2010-12-02 1:19 ` Marcelo Tosatti
2010-12-02 3:44 ` Xiao Guangrong
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