eb23b5ef91
IBRS mitigation for spectre_v2 forces write to MSR_IA32_SPEC_CTRL at every kernel entry/exit. On Enhanced IBRS parts setting MSR_IA32_SPEC_CTRL[IBRS] only once at boot is sufficient. MSR writes at every kernel entry/exit incur unnecessary performance loss. When Enhanced IBRS feature is present, print a warning about this unnecessary performance loss. Signed-off-by: Pawan Gupta <pawan.kumar.gupta@linux.intel.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Reviewed-by: Thadeu Lima de Souza Cascardo <cascardo@canonical.com> Cc: stable@vger.kernel.org Link: https://lore.kernel.org/r/2a5eaf54583c2bfe0edc4fea64006656256cca17.1657814857.git.pawan.kumar.gupta@linux.intel.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.