From a77a94f86273ce42a39cb479217dd8d68acfe0ff Mon Sep 17 00:00:00 2001 From: Borislav Petkov Date: Wed, 25 May 2022 18:12:30 +0200 Subject: x86/microcode: Default-disable late loading It is dangerous and it should not be used anyway - there's a nice early loading already. Requested-by: Peter Zijlstra (Intel) Signed-off-by: Borislav Petkov Signed-off-by: Thomas Gleixner Link: https://lore.kernel.org/r/20220525161232.14924-3-bp@alien8.de --- arch/x86/Kconfig | 11 +++++++++++ 1 file changed, 11 insertions(+) (limited to 'arch/x86/Kconfig') diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig index f423a2d87b15..976309d57a58 100644 --- a/arch/x86/Kconfig +++ b/arch/x86/Kconfig @@ -1350,6 +1350,17 @@ config MICROCODE_AMD If you select this option, microcode patch loading support for AMD processors will be enabled. +config MICROCODE_LATE_LOADING + bool "Late microcode loading (DANGEROUS)" + default n + depends on MICROCODE + help + Loading microcode late, when the system is up and executing instructions + is a tricky business and should be avoided if possible. Just the sequence + of synchronizing all cores and SMT threads is one fragile dance which does + not guarantee that cores might not softlock after the loading. Therefore, + use this at your own risk. Late loading taints the kernel too. + config X86_MSR tristate "/dev/cpu/*/msr - Model-specific register support" help -- cgit v1.2.3