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Date: Wed, 16 Jun 2010 18:51:41 +0800
Message-ID: <AANLkTikZfElLWJvRX2S97FBN2ZVptxg9kYZ7utjHstC6@mail.gmail.com>
Subject: Re: [PATCH 3/6] KVM: MMU: introduce gfn_to_page_atomic() and 
	gfn_to_pfn_atomic()
From: huang ying <huang.ying.caritas@gmail.com>
To: Avi Kivity <avi@redhat.com>
Cc: Xiao Guangrong <xiaoguangrong@cn.fujitsu.com>,
       Marcelo Tosatti <mtosatti@redhat.com>,
       LKML <linux-kernel@vger.kernel.org>, KVM list <kvm@vger.kernel.org>,
       Andi Kleen <andi@firstfloor.org>, Huang Ying <ying.huang@intel.com>
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On Tue, Jun 15, 2010 at 7:22 PM, Avi Kivity <avi@redhat.com> wrote:
> btw, is_hwpoison_address() is racy.  While it looks up the address, some
> other task can unmap the page tables under us.
>
> Andi/Huang?
>
> One way of fixing it is get_user_pages_ptes_fast(), which also returns the
> pte, also atomically.  I want it for other reasons as well (respond to a
> read fault by gupping the page for read, but allowing write access if the
> pte indicates it is writeable).

Yes. is_hwpoison_address() is racy. But I think it is not absolutely
necessary to call is_hwpoison_address() in hva_to_pfn_atomic(), is it?

For is_hwpoison_address() in hva_to_pfn(), we can protect it with mmap_sem.

Best Regards,
Huang Ying
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