Re: [Xen-devel] [PATCH] Make get_page_from_l1e refcount correctly on foreign pagetables.

[Keir Fraser <keir.fraser@xxxxxxxxxxxxx>]

On 13/05/2009 17:07, "Tim Deegan" <Tim.Deegan@xxxxxxxxxx> wrote:

> Hypercalls from dom0 can end up doing resyncs on HVM guests' out-of-sync
> shadow pagetables.  At that point the check against current->domain in
> get_page_from_l1e() triggers the typecount exemption for foreign mappings
> and a writeable typecount gets lost.
> 
> Make the foreign-domain check explicit by having get_page_from_l1e_for(),
> which understands both the dom whose right are being used and the dom
> whose pagetables are being updated.  Most callers of get_page_from_l1e()
> have both the same (instead of one hard-coded to current->domain as before).

The patch doesn't apply to unstable/3.4. Further, the usage of domain
pointers in get_page_from_l1e_for() is now pretty insane -- we have 'd',
'target', 'owner', and still a couple of references to 'current->domain'.
Can we rename some of these, and/or remove redundant variables, and/or add a
function comment explaining what is going on therein, and be really sure
this won't bite us if we check it in so close to 3.4.0? I'm certainly
nervous about it.

 -- Keir



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