4.16-stable review patch. If anyone has any objections, please let me know.
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From: Borislav Petkov bp@suse.de
commit 09e182d17e8891dd73baba961a0f5a82e9274c97 upstream.
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: bb8c13d61a62 ("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 Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- arch/x86/kernel/cpu/microcode/core.c | 6 ++---- 1 file changed, 2 insertions(+), 4 deletions(-)
--- a/arch/x86/kernel/cpu/microcode/core.c +++ b/arch/x86/kernel/cpu/microcode/core.c @@ -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; }
/*