From 09e182d17e8891dd73baba961a0f5a82e9274c97 Mon Sep 17 00:00:00 2001

From: Borislav Petkov <bp@suse.de>

Date: Sat, 21 Apr 2018 10:19:30 +0200

Subject: 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: 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

---

 arch/x86/kernel/cpu/microcode/core.c | 6 ++----

 1 file changed, 2 insertions(+), 4 deletions(-)

diff --git a/arch/x86/kernel/cpu/microcode/core.c b/arch/x86/kernel/cpu/microcode/core.c

index 10c4fc2..77e2013 100644

--- 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;

 	}

 	/*

-- 

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