On 26.02.2024 17:25, Andrew Cooper wrote: > This is long overdue, and we need to start somewhere. > > Signed-off-by: Andrew Cooper <[email protected]>
Acked-by: Jan Beulich <[email protected]> perhaps (nit) with ... > --- /dev/null > +++ b/docs/faq.rst > @@ -0,0 +1,71 @@ > +.. SPDX-License-Identifier: CC-BY-4.0 > + > +Frequently Asked Questions > +========================== > + > +How do I... > +----------- > + > +... check whether a Kconfig option is active? > +^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ > + > + Kconfig is a build time configuration system, combining inherent knowledge, > + the capabilities of the toolchain, and explicit user choice to form a > + configuration of a build of Xen. > + > + A file, by default ``.config``, is produced by the build identifying the > + configuration used. Kconfig symbols all start with ``CONFIG_``, and come > in > + a variety of types including strings, integers and booleans. Booleans are > + the most common, and when active are expressed with ``...=y``. e.g.:: > + > + xen.git/xen$ grep CONFIG_FOO .config > + CONFIG_FOO_BOOLEAN=y > + CONFIG_FOO_STRING="lorem ipsum" > + CONFIG_FOO_INTEGER=42 > + > + Symbols which are either absent, or expressed as ``... is not set`` are > + disabled. e.g.:: > + > + xen.git/xen$ grep CONFIG_BAR .config > + # CONFIG_BAR is not set > + > + Builds of Xen configured with ``CONFIG_HYPFS_CONFIG=y`` embed their own > + ``.config`` at build time, and can provide it to the :term:`control domain` > + upon requested. e.g.:: > + > + [root@host ~]# xenhypfs cat /buildinfo/config | grep -e FOO -e BAR > + CONFIG_FOO=y > + # CONFIG_BAR is not set > + > + > +... tell if CET is active? > +^^^^^^^^^^^^^^^^^^^^^^^^^^ > + > + Control-flow Enforcement Technology support was added to Xen 4.14. It is > + build time conditional, dependent on both having a new-enough toolchain and > + an explicit Kconfig option, and also requires capable hardware. See > + :term:`CET`. > + > + For CET-SS, Shadow Stacks, the minimum toolchain requirements are > ``binutils > + >= 2.29`` or ``LLVM >= 6``. No specific compiler support is required. > + Check for ``CONFIG_XEN_SHSTK`` being active. > + > + For CET-IBT, Indirect Branch Tracking, the minimum toolchain requirements > + are ``GCC >= 9`` and ``binutils >= 2.29``. Xen relies on a compiler > feature > + which is specific to GCC at the time of writing. Check for > + ``CONFIG_XEN_IBT`` being active. > + > + If a capable Xen with booted on capable hardware, and CET is not disabled > by ... s/with/is/ (or "was"). Jan
