Re: [Xen-devel] bogus gfn - mfn - gfn - mfn checks in guest_physmap_add_entry

[Tim Deegan <Tim.Deegan@xxxxxxxxxx>]

At 15:03 +0000 on 25 Nov (1290697390), Olaf Hering wrote:
> On Wed, Nov 24, Tim Deegan wrote:
> 
> > The problem is that PV guests set their own m2p entries and can't be
> > relied on to tear them down.  
> 
> What needs to happen for PV guests?
> Dont they use the machine_to_phys_mapping[] array like HVM guests?

They do, but they can put whatever they like in it, and don't have to
clean up afterwards.

> I see memory_exchange uses assign_pages() to move mfns from one domain
> to another (havent studied the whole function yet). I think thats
> another place that needs an audit wether the machine_to_phys_mapping[]
> array is maintained properly.

Good catch.  It might be better to hook page_set_owner(), which ought to
imply that the old m2p info is stale.   I had a quick look at all its
callers and I _think_ it would be OK, but I haven't tested that at 
all. :)

Tim.

-- 
Tim Deegan <Tim.Deegan@xxxxxxxxxx>
Principal Software Engineer, Xen Platform Team
Citrix Systems UK Ltd.  (Company #02937203, SL9 0BG)

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