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afa8b475c1
KVM guests with commitc8c4076723("x86/timer: Skip PIT initialization on modern chipsets") applied to guest kernel have been observed to have unusually higher CPU usage with symptoms of increase in vm exits for HLT and MSW_WRITE (MSR_IA32_TSCDEADLINE). This is caused by older QEMUs lacking support for X86_FEATURE_ARAT. lapic clock retains CLOCK_EVT_FEAT_C3STOP and nohz stays inactive. There's no usable broadcast device either. Do the PIT initialization if guest CPU lacks X86_FEATURE_ARAT. On real hardware it shouldn't matter as ARAT and DEADLINE come together. Fixes:c8c4076723("x86/timer: Skip PIT initialization on modern chipsets") Signed-off-by: Jan Stancek <jstancek@redhat.com> Signed-off-by: Thomas Gleixner <tglx@linutronix.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.