linux-kernel - Re: [PATCH 3/6] KVM: MMU: introduce gfn_to_page_atomic() and gfn_to_pfn

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Message-ID: <AANLkTikZfElLWJvRX2S97FBN2ZVptxg9kYZ7utjHstC6@mail.gmail.com>
Date:	Wed, 16 Jun 2010 18:51:41 +0800
From:	huang ying <huang.ying.caritas@...il.com>
To:	Avi Kivity <avi@...hat.com>
Cc:	Xiao Guangrong <xiaoguangrong@...fujitsu.com>,
	Marcelo Tosatti <mtosatti@...hat.com>,
	LKML <linux-kernel@...r.kernel.org>,
	KVM list <kvm@...r.kernel.org>,
	Andi Kleen <andi@...stfloor.org>,
	Huang Ying <ying.huang@...el.com>
Subject: Re: [PATCH 3/6] KVM: MMU: introduce gfn_to_page_atomic() and 
	gfn_to_pfn_atomic()

On Tue, Jun 15, 2010 at 7:22 PM, Avi Kivity <avi@...hat.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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