From: Keir Fraser <keir.fraser@eu.citrix.com>
To: Tim Deegan <Tim.Deegan@eu.citrix.com>
Cc: Gianluca Guida <Gianluca.Guida@eu.citrix.com>,
"Jiang, Yunhong" <yunhong.jiang@intel.com>,
"xen-devel@lists.xensource.com" <xen-devel@lists.xensource.com>
Subject: Re: Re: [PATCH]Add a flag for shadow pages
Date: Wed, 04 Mar 2009 13:19:17 +0000 [thread overview]
Message-ID: <C5D43055.3BEE%keir.fraser@eu.citrix.com> (raw)
In-Reply-To: <20090304121317.GB6322@york.uk.xensource.com>
On 04/03/2009 12:13, "Tim Deegan" <Tim.Deegan@eu.citrix.com> wrote:
> shadow_get_page_from_l1e() should never be handling a pointer to a
> shadow -- if it does that then we've let the guest see the shadows and
> all invariants go out the window.
>
> sh_mfn_is_a_pagetable() looks OK too; it only gets called based on the
> contents of shadow PTEs or the MFNs that guests are writing to, both of
> which should be safe.
>
> It all feels a bit fragile to me though, compared to the old layout
> where we always knew the owner field would be NULL.
This is the tradeoff for the new get_page() implementation and wider
reference counts. We just need to be careful and use
page_get_owner_and_reference() in the few cases it seems to be needed.
-- Keir
next prev parent reply other threads:[~2009-03-04 13:19 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-03-04 8:46 [PATCH]Add a flag for shadow pages Jiang, Yunhong
2009-03-04 9:06 ` Keir Fraser
2009-03-04 9:17 ` Jiang, Yunhong
2009-03-04 9:22 ` Keir Fraser
2009-03-04 9:28 ` Jiang, Yunhong
2009-03-04 9:56 ` Keir Fraser
2009-03-04 11:57 ` Keir Fraser
2009-03-04 12:13 ` Tim Deegan
2009-03-04 13:19 ` Keir Fraser [this message]
2009-03-04 14:30 ` Keir Fraser
2009-03-04 16:01 ` Jiang, Yunhong
2009-03-04 16:32 ` Gianluca Guida
2009-03-05 2:41 ` Jiang, Yunhong
2009-03-04 16:45 ` Keir Fraser
2009-03-04 9:20 ` Keir Fraser
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