Re: [Xen-devel] error in xen/arch/x86/mm.c:get_page during migration

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 28.02.13 at 15:59, Andres Lagar-Cavilla <andreslc@xxxxxxxxxxxxxx> wrote:
> On Feb 28, 2013, at 9:06 AM, "Jan Beulich" <JBeulich@xxxxxxxx> wrote:
> 
>>>>> On 28.02.13 at 12:56, Tim Deegan <tim@xxxxxxx> wrote:
>>> At 09:52 -0500 on 25 Feb (1361785966), Andres Lagar-Cavilla wrote:
>>>> There seems to be something else amiss though. Unless I am parsing
>>>> this incorrectly, taf == PGT_writable | PGT_pae_xen_l2? And caf == PAT
>>>> | PCD? Looks like a very unlikely combination
>>> 
>>> By my reading, 
>>> 
>>> taf = 0x7400000000000001 = typecount 1, PGT_writable_page | PGT_validated
>>> caf = 0x0180000000000000 = refcount 0, PGC_state_free
>> 
>> Right.
> D'oh :)
> 
> Sharing code never sets PGT_writable, only sets/clears PGT_shared. I tend to 
> think the dom_cow rd belies a different problem. To use dom_cow, the domain 
> has to have an explicit domctl that enables memory sharing.

In that case, Olaf, could you simply set dom_cow to some invalid
pointer right after it got set up through domain_create(), so that
any dereference of it would blow up? That might be the faster path
towards finding the first bogus use.

Jan


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