iommu/sva: Track mm changes with an MMU notifier

hulk inclusion
category: feature
bugzilla: 14369
CVE: NA
-------------------

When creating an io_mm structure, register an MMU notifier that informs
us when the virtual address space changes and disappears.

Add a new operation to the IOMMU driver, mm_invalidate, called when a
range of addresses is unmapped to let the IOMMU driver send ATC
invalidations. mm_invalidate cannot sleep.

Adding the notifier complicates io_mm release. In one case device
drivers free the io_mm explicitly by calling unbind (or detaching the
device from its domain). In the other case the process could crash
before unbind, in which case the release notifier has to do all the
work.

Allowing the device driver's mm_exit() handler to sleep adds another
complication, but it will greatly simplify things for users. For example
VFIO can take the IOMMU mutex and remove any trace of io_mm, instead of
introducing complex synchronization to delicatly handle this race. But
relaxing the user side does force unbind() to sleep and wait for all
pending mm_exit() calls to finish.

Signed-off-by: Jean-Philippe Brucker <jean-philippe.brucker@arm.com>
Signed-off-by: Fang Lijun <fanglijun3@huawei.com>
Reviewed-by: Hanjun Guo <guohanjun@huawei.com>
Reviewed-by: Zhen Lei <thunder.leizhen@huawei.com>
Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>