Re: [Xen-devel] Deadlocks by p2m_lock and event_lock

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 13.03.12 at 19:26, "Andres Lagar-Cavilla" <andres@xxxxxxxxxxxxxxxx> 
>>> wrote:
>>  Hi, Tim and Andres
>> The patch fix part of this issue. In handle_mmio, function hvmemul_do_io()
>> is called and p2m lock was held again by calling get_gfn_unshare(), still
>> trigger a deadlocks.
> 
> I have a question before I dive into lock untangling
> 
> msix_capability_init ->
> p2m_change_entry_type_global(dev->domain, p2m_mmio_direct, p2m_mmio_direct);
> 
> Huh? This achieves ... nothing. Almost. It flushes a bunch of TLBs, but
> that can be done with significantly less effort. Am I missing something?

Yes - the purpose of this isn't to flush any TLBs, but to enforce the
immediately preceding addition to the mmio_ro_ranges range set.

Jan


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