587dadb43c
commit a01994f5e5c79d3a35e5e8cf4252c7f2147323c3 upstream. Kyle reported that rr[0] has started to malfunction on Comet Lake and later CPUs due to EFI starting to make use of CPL3 [1] and the PMU event filtering not distinguishing between regular CPL3 and SMM CPL3. Since this is a privilege violation, default disable SMM visibility where possible. Administrators wanting to observe SMM cycles can easily change this using the sysfs attribute while regular users don't have access to this file. [0] https://rr-project.org/ [1] See the Intel white paper "Trustworthy SMM on the Intel vPro Platform" at https://bugzilla.kernel.org/attachment.cgi?id=300300, particularly the end of page 5. Reported-by: Kyle Huey <me@kylehuey.com> Suggested-by: Andrew Cooper <Andrew.Cooper3@citrix.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: stable@kernel.org Link: https://lkml.kernel.org/r/YfKChjX61OW4CkYm@hirez.programming.kicks-ass.net Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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.