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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: bb8c13d61a ("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
This commit is contained in:
Borislav Petkov 2018-04-21 10:19:30 +02:00 committed by Thomas Gleixner
parent 84749d8375
commit 09e182d17e
1 changed files with 2 additions and 4 deletions
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6
arch/x86/kernel/cpu/microcode/core.c
View File

@ -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;
}
/*