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After updating microcode on one of the threads of a core, the other thread sibling automatically gets the update since the microcode resources on a hyperthreaded core are shared between the two threads. Check the microcode revision on the CPU before performing a microcode update and thus save us the WRMSR 0x79 because it is a particularly expensive operation. [ Borislav: Massage changelog and coding style. ] Signed-off-by: Ashok Raj <ashok.raj@intel.com> Signed-off-by: Borislav Petkov <bp@suse.de> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Tested-by: Tom Lendacky <thomas.lendacky@amd.com> Tested-by: Ashok Raj <ashok.raj@intel.com> Cc: Arjan Van De Ven <arjan.van.de.ven@intel.com> Link: http://lkml.kernel.org/r/1519352533-15992-2-git-send-email-ashok.raj@intel.com Link: https://lkml.kernel.org/r/20180228102846.13447-3-bp@alien8.de
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.