Patch "x86/apic: Do not init irq remapping if ioapic is disabled" has been added to the 4.4-stable tree

This is a note to let you know that I've just added the patch titled

x86/apic: Do not init irq remapping if ioapic is disabled

to the 4.4-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
x86-apic-do-not-init-irq-remapping-if-ioapic-is-disabled.patch
and it can be found in the queue-4.4 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Wanpeng Li <[email protected]>
Date: Tue, 23 Aug 2016 20:07:19 +0800
Subject: x86/apic: Do not init irq remapping if ioapic is disabled

From: Wanpeng Li <[email protected]>

commit 2e63ad4bd5dd583871e6602f9d398b9322d358d9 upstream.

native_smp_prepare_cpus
-> default_setup_apic_routing

    -> enable_IR_x2apic
      -> irq_remapping_prepare
        -> intel_prepare_irq_remapping
          -> intel_setup_irq_remapping

So IR table is setup even if "noapic" boot parameter is added. As a result we crash later when the interrupt affinity is set due to a half initialized remapping infrastructure.

Prevent remap initialization when IOAPIC is disabled.

---
 arch/x86/kernel/apic/apic.c |    3 +++
 1 file changed, 3 insertions(+)

@@ -1587,6 +1587,9 @@ void __init enable_IR_x2apic(void)
 	unsigned long flags;
 	int ret, ir_stat;
 
+	if (skip_ioapic_setup)
+		return;
+
 	ir_stat = irq_remapping_prepare();
 	if (ir_stat < 0 && !x2apic_supported())
 		return;

Patches currently in stable-queue which might be from [email protected] are

queue-4.4/x86-apic-do-not-init-irq-remapping-if-ioapic-is-disabled.patch