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While enabled to count events and an event occurrence causes the counter value to increment and roll over to or past zero, this is termed a counter overflow. The overflow can trigger an interrupt. The IOMMU perfmon needs to handle the case properly. New HW IRQs are allocated for each IOMMU device for perfmon. The IRQ IDs are after the SVM range. In the overflow handler, the counter is not frozen. It's very unlikely that the same counter overflows again during the period. But it's possible that other counters overflow at the same time. Read the overflow register at the end of the handler and check whether there are more. Signed-off-by: Kan Liang <kan.liang@linux.intel.com> Link: https://lore.kernel.org/r/20230128200428.1459118-7-kan.liang@linux.intel.com Signed-off-by: Lu Baolu <baolu.lu@linux.intel.com> Signed-off-by: Joerg Roedel <jroedel@suse.de>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.