Re: Deadlocks by p2m_lock and event_lock

["Andres Lagar-Cavilla" <andres@lagarcavilla.org>]

>>>> On 13.03.12 at 19:26, "Andres Lagar-Cavilla" <andres@lagarcavilla.org>
>>>> 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.

Because p2m entries of type mmio_direct have their permissions
(re)computed as a function of rangesets. Got it. Thanks.

Andres
>
> Jan
>
>