iommu: handle page response timeout

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

When IO page faults are reported outside IOMMU subsystem, the page
request handler may fail for various reasons. E.g. a guest received
page requests but did not have a chance to run for a long time. The
irresponsive behavior could hold off limited resources on the pending
device.
There can be hardware or credit based software solutions as suggested
in the PCI ATS Ch-4. To provide a basic safety net this patch
introduces a per device deferrable timer which monitors the longest
pending page fault that requires a response. Proper action such as
sending failure response code could be taken when timer expires but not
included in this patch. We need to consider the life cycle of page
groupd ID to prevent confusion with reused group ID by a device.
For now, a warning message provides clue of such failure.

Signed-off-by: Jacob Pan <jacob.jun.pan@linux.intel.com>
Signed-off-by: Ashok Raj <ashok.raj@intel.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>