Linux kernel ============ This file was moved to Documentation/admin-guide/README.rst Please notice that there are several guides for kernel developers and users. These guides can be rendered in a number of formats, like HTML and PDF. In order to build the documentation, use ``make htmldocs`` or ``make pdfdocs``. There are various text files in the Documentation/ subdirectory, several of them using the Restructured Text markup notation. See Documentation/00-INDEX for a list of what is contained in each file. 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.
Borislav Petkov
authored
Emanuel reported an issue with a hang during microcode update because my dumb idea to use one atomic synchronization variable for both rendezvous - before and after update - was simply bollocks: microcode: microcode_reload_late: late_cpus: 4 microcode: __reload_late: cpu 2 entered microcode: __reload_late: cpu 1 entered microcode: __reload_late: cpu 3 entered microcode: __reload_late: cpu 0 entered microcode: __reload_late: cpu 1 left microcode: Timeout while waiting for CPUs rendezvous, remaining: 1 CPU1 above would finish, leave and the others will still spin waiting for it to join. So do two synchronization atomics instead, which makes the code a lot more straightforward. Also, since the update is serialized and it also takes quite some time per microcode engine, increase the exit timeout by the number of CPUs on the system. That's ok because the moment all CPUs are done, that timeout will be cut short. Furthermore, panic when some of the CPUs timeout when returning from a microcode update: we can't allow a system with not all cores updated. Also, as an optimization, do not do the exit sync if microcode wasn't updated. Reported-by:Emanuel Czirai <xftroxgpx@protonmail.com> Signed-off-by:
Borislav Petkov <bp@suse.de> Signed-off-by:
Thomas Gleixner <tglx@linutronix.de> Tested-by:
Ashok Raj <ashok.raj@intel.com> Tested-by:
Tom Lendacky <thomas.lendacky@amd.com> Link: https://lkml.kernel.org/r/20180314183615.17629-2-bp@alien8.de
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