d19b3ad02c
One of the reasons that dlpar_cpu_offline can fail is when attempting to offline the last online CPU of the kernel. This can be observed in a pseries QEMU guest that has hotplugged CPUs. If the user offlines all other CPUs of the guest, and a hotplugged CPU is now the last online CPU, trying to reclaim it will fail. The current error message in this situation returns rc with -EBUSY and a generic explanation, e.g.: pseries-hotplug-cpu: Failed to offline CPU PowerPC,POWER9, rc: -16 EBUSY can be caused by other conditions, such as cpu_hotplug_disable being true. Throwing a more specific error message for this case, instead of just "Failed to offline CPU", makes it clearer that the error is in fact a known error situation instead of other generic/unknown cause. This patch adds a 'last online' check in dlpar_cpu_offline() to catch the 'last online CPU' offline error, eturning a more informative error message: pseries-hotplug-cpu: Unable to remove last online CPU PowerPC,POWER9 Signed-off-by: Daniel Henrique Barboza <danielhb413@gmail.com> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> Link: https://lore.kernel.org/r/20210323205056.52768-2-danielhb413@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.