From abfdcc849a720f36bbb075ee35d64e84314387fe Mon Sep 17 00:00:00 2001 From: Borislav Petkov Date: Wed, 25 May 2022 18:12:31 +0200 Subject: [PATCH 06/36] x86/microcode: Taint and warn on late loading Warn before it is attempted and taint the kernel. Late loading microcode can lead to malfunction of the kernel when the microcode update changes behaviour. There is no way for the kernel to determine whether its safe or not. Signed-off-by: Borislav Petkov Signed-off-by: Thomas Gleixner Link: https://lore.kernel.org/r/20220525161232.14924-4-bp@alien8.de (cherry picked from commit d23d33ea0fcdc4bbb484990bf53867f99c63ccab) Signed-off-by: Mridula Shastry Reviewed-by: Todd Vierling --- arch/x86/kernel/cpu/microcode/core.c | 5 +++++ 1 file changed, 5 insertions(+) diff --git a/arch/x86/kernel/cpu/microcode/core.c b/arch/x86/kernel/cpu/microcode/core.c index c4d19f4b7afb..a803b839b16e 100644 --- a/arch/x86/kernel/cpu/microcode/core.c +++ b/arch/x86/kernel/cpu/microcode/core.c @@ -513,6 +513,9 @@ static int microcode_reload_late(void) { int ret; + pr_err("Attempting late microcode loading - it is dangerous and taints the kernel.\n"); + pr_err("You should switch to early loading, if possible.\n"); + atomic_set(&late_cpus_in, 0); atomic_set(&late_cpus_out, 0); @@ -561,6 +564,8 @@ put: if (ret >= 0) ret = size; + add_taint(TAINT_CPU_OUT_OF_SPEC, LOCKDEP_STILL_OK); + return ret; } -- 2.39.3