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Re: [Xen-devel] Re: [PATCH]Add a flag for shadow pages

To: "Jiang, Yunhong" <yunhong.jiang@xxxxxxxxx>, Tim Deegan <Tim.Deegan@xxxxxxxxxxxxx>, Gianluca Guida <Gianluca.Guida@xxxxxxxxxxxxx>
Subject: Re: [Xen-devel] Re: [PATCH]Add a flag for shadow pages
From: Keir Fraser <keir.fraser@xxxxxxxxxxxxx>
Date: Wed, 04 Mar 2009 16:45:30 +0000
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Thread-topic: [Xen-devel] Re: [PATCH]Add a flag for shadow pages
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On 04/03/2009 16:01, "Jiang, Yunhong" <yunhong.jiang@xxxxxxxxx> wrote:

> Thanks for your really quick-hand implementation. I will update my another
> patch accordingly tomorrow.
> 
> So still one question to the two assertion (or to Tim??) in
> sh_rm_write_access_from_sl1p()/sh_put_ref(). What's the potential error to be
> protected by this checking? If page is a shadow, it's count_info will always
> be 0, right? Or it is just a sanity checking?
> 
> I need change this is because, if we mark a page offline, then the count_info
> is not 0, even for shadow page. Can I just checking the count_mask here?

Current shadow pages always have count_info == 0. If you add in extra flags
that you want preserved in shadow pages, you'll need some modifications like
in your last patch.

 -- Keir



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