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The perf subsystem assumes that all counters are by default per-CPU. So the user space tool reads a counter from each CPU. However, the IOMMU counters are system-wide and can be read from any CPU. Here we use a CPU mask to restrict counting to one CPU to handle the issue. (with CPU hotplug notifier to choose a different CPU if the chosen one is taken off-line). The CPU is exposed to /sys/bus/event_source/devices/dmar*/cpumask for the user space perf tool. Signed-off-by: Kan Liang <kan.liang@linux.intel.com> Link: https://lore.kernel.org/r/20230128200428.1459118-6-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.