839d893b40
KVM PR does not implement address translation modes on interrupt, so it must not allow H_SET_MODE to succeed. The behaviour change caused by this mode is architected and not advisory (interrupts *must* behave differently). QEMU does not deal with differences in AIL support in the host. The solution to that is a spapr capability and corresponding KVM CAP, but this patch does not break things more than before (the host behaviour already differs, this change just disallows some modes that are not implemented properly). By happy coincidence, this allows PR Linux guests that are using the SCV facility to boot and run, because Linux disables the use of SCV if AIL can not be set to 3. This does not fix the underlying problem of missing SCV support (an OS could implement real-mode SCV vectors and try to enable the facility). The true fix for that is for KVM PR to emulate scv interrupts from the facility unavailable interrupt. Signed-off-by: Nicholas Piggin <npiggin@gmail.com> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> Reviewed-by: Fabiano Rosas <farosas@linux.ibm.com> Link: https://lore.kernel.org/r/20220222064727.2314380-3-npiggin@gmail.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.