1cade527f6
PowerISA v3.1 has few updates for the Branch History Rolling Buffer(BHRB). BHRB disable is controlled via Monitor Mode Control Register A (MMCRA) bit, namely "BHRB Recording Disable (BHRBRD)". This field controls whether BHRB entries are written when BHRB recording is enabled by other bits. This patch implements support for this BHRB disable bit. By setting 0b1 to this bit will disable the BHRB and by setting 0b0 to this bit will have BHRB enabled. This addresses backward compatibility (for older OS), since this bit will be cleared and hardware will be writing to BHRB by default. This patch addresses changes to set MMCRA (BHRBRD) at boot for power10 (there by the core will run faster) and enable this feature only on runtime ie, on explicit need from user. Also save/restore MMCRA in the restore path of state-loss idle state to make sure we keep BHRB disabled if it was not enabled on request at runtime. Signed-off-by: Athira Rajeev <atrajeev@linux.vnet.ibm.com> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> Link: https://lore.kernel.org/r/1594996707-3727-12-git-send-email-atrajeev@linux.vnet.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.