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From: Xiao Guangrong <xiaoguangrong@cn.fujitsu.com>
To: Avi Kivity <avi@redhat.com>
Cc: Marcelo Tosatti <mtosatti@redhat.com>,
	LKML <linux-kernel@vger.kernel.org>, KVM <kvm@vger.kernel.org>
Subject: Re: [PATCH v2 2/6] KVM: MMU: don't drop spte if overwrite it from W to RO
Date: Thu, 18 Nov 2010 15:12:56 +0800	[thread overview]
Message-ID: <4CE4D1F8.7090701@cn.fujitsu.com> (raw)
In-Reply-To: <4CE3FB74.8050705@redhat.com>

On 11/17/2010 11:57 PM, Avi Kivity wrote:

>>>   set_pte:
>>>       update_spte(sptep, spte);
>>> +    /*
>>> +     * If we overwrite a writable spte with a read-only one we
>>> +     * should flush remote TLBs. Otherwise rmap_write_protect
>>> +     * will find a read-only spte, even though the writable spte
>>> +     * might be cached on a CPU's TLB.
>>> +     */
>>> +    if (is_writable_pte(entry)&&  !is_writable_pte(*sptep))
>>> +        kvm_flush_remote_tlbs(vcpu->kvm);
>> There is no need to flush on sync_page path since the guest is
>> responsible for it.
>>
> 
>  If we don't, the next rmap_write_protect() will incorrectly decide that
> there's no need to flush tlbs.
> 

Maybe it's not a problem if guest can flush all tlbs after overwrite it?
Marcelo, what's your comment about this?

  reply	other threads:[~2010-11-18  7:08 UTC|newest]

Thread overview: 22+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2010-11-17  4:10 [PATCH v2 1/6] KVM: MMU: fix forgot flush vcpu tlbs Xiao Guangrong
2010-11-17  4:10 ` [PATCH v2 2/6] KVM: MMU: don't drop spte if overwrite it from W to RO Xiao Guangrong
2010-11-17 15:42   ` Marcelo Tosatti
2010-11-17 15:57     ` Avi Kivity
2010-11-18  7:12       ` Xiao Guangrong [this message]
2010-11-18 15:32         ` Marcelo Tosatti
2010-11-18 16:41           ` Avi Kivity
2010-11-17  4:11 ` [PATCH v2 3/6] KVM: MMU: don't mark spte notrap if reserved bit set Xiao Guangrong
2010-11-17 15:56   ` Marcelo Tosatti
2010-11-17  4:12 ` [PATCH v2 4/6] KVM: MMU: rename 'reset_host_protection' to 'host_writable' Xiao Guangrong
2010-11-17 15:58   ` Marcelo Tosatti
2010-11-17  4:13 ` [PATCH v2 5/6] KVM: MMU: remove 'clear_unsync' parameter Xiao Guangrong
2010-11-17 16:49   ` Marcelo Tosatti
2010-11-18  7:42     ` Xiao Guangrong
2010-11-18 15:43       ` Marcelo Tosatti
2010-11-17  4:13 ` [PATCH v2 6/6] KVM: MMU: cleanup update_pte, pte_prefetch and sync_page functions Xiao Guangrong
2010-11-17 16:55   ` Marcelo Tosatti
2010-11-17 15:29 ` [PATCH v2 1/6] KVM: MMU: fix forgot flush vcpu tlbs Marcelo Tosatti
2010-11-17 16:26   ` Avi Kivity
2010-11-17 17:36     ` Marcelo Tosatti
2010-11-18  7:17       ` Xiao Guangrong
2010-11-18  9:32         ` Avi Kivity

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