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commit 634ac23ad609b3ddd9e0e478bd5afbf49d3a2556 upstream On CPUs where microcode loading is not NMI-safe the SMT siblings which are parked in one of the play_dead() variants still react to NMIs. So if an NMI hits while the primary thread updates the microcode the resulting behaviour is undefined. The default play_dead() implementation on modern CPUs is using MWAIT which is not guaranteed to be safe against a microcode update which affects MWAIT. Take the cpus_booted_once_mask into account to detect this case and refuse to load late if the vendor specific driver does not advertise that late loading is NMI safe. AMD stated that this is safe, so mark the AMD driver accordingly. This requirement will be partially lifted in later changes. Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de> Link: https://lore.kernel.org/r/20231002115903.087472735@linutronix.de Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.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.