[ck] [patch v1] x86/apic: Mask IOAPIC entries when disabling the local APIC

commit 0f378d73d429d5f73fe2f00be4c9a15dbe9779ee upstream. When a system suspends, the local APIC is disabled in the suspend sequence, but the IOAPIC is left in the current state. This means unmasked interrupt lines stay unmasked. This is usually the case for IOAPIC pin 9 to which the ACPI interrupt is connected. That means that in suspended state the IOAPIC can respond to an external interrupt, e.g. the wakeup via keyboard/RTC/ACPI, but the interrupt message cannot be handled by the disabled local APIC. As a consequence the Remote IRR bit is set, but the local APIC does not send an EOI to acknowledge it. This causes the affected interrupt line to become stale and the stale Remote IRR bit will cause a hang when __synchronize_hardirq() is invoked for that interrupt line. To prevent this, mask all IOAPIC entries before disabling the local APIC. The resume code already has the unmask operation inside. [ tglx: Massaged changelog ] Signed-off-by: Tony W Wang-oc <TonyWWang-oc(a)zhaoxin.com> Signed-off-by: Thomas Gleixner <tglx(a)linutronix.de> Link: https://lore.kernel.org/r/1579076539-7267-1-git-send-email-TonyWWang-oc@zha… Signed-off-by: LeoLiu-oc <LeoLiu-oc(a)zhaoxin.com> --- arch/x86/kernel/apic/apic.c | 7 +++++++ 1 file changed, 7 insertions(+) diff --git a/arch/x86/kernel/apic/apic.c b/arch/x86/kernel/apic/apic.c index fe19098fc35d..236399ad53df 100644 --- a/arch/x86/kernel/apic/apic.c +++ b/arch/x86/kernel/apic/apic.c @@ -2577,6 +2577,13 @@ static int lapic_suspend(void) #endif local_irq_save(flags); + + /* + * Mask IOAPIC before disabling the local APIC to prevent stale IRR + * entries on some implementations. + */ + mask_ioapic_entries(); + disable_local_APIC(); irq_remapping_disable(); -- 2.20.1