6a77d38efc
On systems with KPTI enabled, we can currently observe the following warning: BUG: using smp_processor_id() in preemptible caller is invalidate_user_asid+0x13/0x50 CPU: 6 PID: 1075 Comm: dmesg Not tainted 5.12.0-rc4-gda4a2b1a5479-kfence_1+ #1 Hardware name: Hewlett-Packard HP Pro 3500 Series/2ABF, BIOS 8.11 10/24/2012 Call Trace: dump_stack+0x7f/0xad check_preemption_disabled+0xc8/0xd0 invalidate_user_asid+0x13/0x50 flush_tlb_one_kernel+0x5/0x20 kfence_protect+0x56/0x80 ... While it normally makes sense to require preemption to be off, so that the expected CPU's TLB is flushed and not another, in our case it really is best-effort (see comments in kfence_protect_page()). Avoid the warning by disabling preemption around flush_tlb_one_kernel(). Link: https://lore.kernel.org/lkml/YGIDBAboELGgMgXy@elver.google.com/ Link: https://lkml.kernel.org/r/20210330065737.652669-1-elver@google.com Signed-off-by: Marco Elver <elver@google.com> Reported-by: Tomi Sarvela <tomi.p.sarvela@intel.com> Cc: Alexander Potapenko <glider@google.com> Cc: Dmitry Vyukov <dvyukov@google.com> Cc: Andrey Konovalov <andreyknvl@google.com> Cc: Jann Horn <jannh@google.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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.