Re: [PATCH 3/7] vfio/pci: Use vfio_device_unmap_mapping_range()

Christoph Hellwig
2021-08-10T08:52:00Z

On Fri, Aug 06, 2021 at 02:17:45PM -0600, Alex Williamson wrote:
> > Now that this is simplified so much, I wonder if we can drop the
> > memory_lock and just use the dev_set->lock?
> >
> > That avoids the whole down_write_trylock thing and makes it much more
> > understandable?
>
> Hmm, that would make this case a lot easier, but using a mutex,
> potentially shared across multiple devices, taken on every non-mmap
> read/write doesn't really feel like a good trade-off when we're
> currently using a per device rwsem to retain concurrency here. Thanks,

Using a per-set percpu_rw_semaphore might be a good plan here. Probably
makes sense to do that incrementally after this change, though.