x86/microcode: Update late microcode in parallel
Microcode update was changed to be serialized due to restrictions after Spectre days. Updating serially on a large multi-socket system can be painful since it is being done on one CPU at a time. Cloud customers have expressed discontent as services disappear for a prolonged time. The restriction is that only one core (or only one thread of a core in the case of an SMT system) goes through the update while other cores (or respectively, SMT threads) are quiesced. Do the microcode update only on the first thread of each core while other siblings simply wait for this to complete. [ bp: Simplify, massage, cleanup comments. ] Signed-off-by: Ashok Raj <ashok.raj@intel.com> Signed-off-by: Mihai Carabas <mihai.carabas@oracle.com> Signed-off-by: Borislav Petkov <bp@suse.de> Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com> Cc: "H. Peter Anvin" <hpa@zytor.com> Cc: Ingo Molnar <mingo@redhat.com> Cc: Jon Grimm <Jon.Grimm@amd.com> Cc: kanth.ghatraju@oracle.com Cc: konrad.wilk@oracle.com Cc: patrick.colp@oracle.com Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Tom Lendacky <thomas.lendacky@amd.com> Cc: x86-ml <x86@kernel.org> Link: https://lkml.kernel.org/r/1566506627-16536-2-git-send-email-mihai.carabas@oracle.com
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