Commit 09e182d1 authored Apr 21, 2018 by Borislav Petkov Committed by Thomas Gleixner Apr 24, 2018

x86/microcode: Do not exit early from __reload_late()



Vitezslav reported a case where the

  "Timeout during microcode update!"

panic would hit. After a deeper look, it turned out that his .config had
CONFIG_HOTPLUG_CPU disabled which practically made save_mc_for_early() a
no-op.

When that happened, the discovered microcode patch wasn't saved into the
cache and the late loading path wouldn't find any.

This, then, lead to early exit from __reload_late() and thus CPUs waiting
until the timeout is reached, leading to the panic.

In hindsight, that function should have been written so it does not return
before the post-synchronization. Oh well, I know better now...

Fixes: bb8c13d6 ("x86/microcode: Fix CPU synchronization routine")
Reported-by: Vitezslav Samel <vitezslav@samel.cz>
Signed-off-by: Borislav Petkov <bp@suse.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Vitezslav Samel <vitezslav@samel.cz>
Tested-by: Ashok Raj <ashok.raj@intel.com>
Cc: stable@vger.kernel.org
Link: http://lkml.kernel.org/r/20180418081140.GA2439@pc11.op.pod.cz
Link: https://lkml.kernel.org/r/20180421081930.15741-2-bp@alien8.de

parent 84749d83

arch/x86/kernel/cpu/microcode/core.c

+2 −4

Original line number	Diff line number	Diff line
		@@ -564,14 +564,12 @@ static int __reload_late(void *info)
		apply_microcode_local(&err);
		spin_unlock(&update_lock);

		/* siblings return UCODE_OK because their engine got updated already */
		if (err > UCODE_NFOUND) {
		pr_warn("Error reloading microcode on CPU %d\n", cpu);
		return -1;
		/* siblings return UCODE_OK because their engine got updated already */
		ret = -1;
		} else if (err == UCODE_UPDATED \|\| err == UCODE_OK) {
		ret = 1;
		} else {
		return ret;
		}

		/*