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LDBAR is a per-thread SPR populated and used by the thread-imc pmu driver to dump the data counter into memory. It contains memory along with few other configuration bits. LDBAR is populated and enabled only when any of the thread imc pmu events are monitored. In ultravisor enabled systems, LDBAR becomes ultravisor privileged and an attempt to write to it will cause a Hypervisor Emulation Assistance interrupt. In ultravisor enabled systems, the ultravisor is responsible to maintain the LDBAR (e.g. save and restore it). This restricts LDBAR access to only when ultravisor is disabled. Signed-off-by: Claudio Carvalho <cclaudio@linux.ibm.com> Reviewed-by: Ram Pai <linuxram@us.ibm.com> Reviewed-by: Ryan Grimm <grimm@linux.ibm.com> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> Link: https://lore.kernel.org/r/20190822034838.27876-7-cclaudio@linux.ibm.com
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.