[PATCH v1] x86, ioapic: fix kernel crash on boot on non-PC platforms

[Andy Shevchenko <andriy.shevchenko@linux.intel.com>]

Intel MID platforms have no legacy IRQ support. The commit bfa644bfa9e3 (x86,
irq: Convert IOAPIC to use hierarchy irqdomain interfaces) introduces new
scheme of allocating IRQs for IOAPIC, though it maps a pin disregarding whether
or not the platform supports legacy IRQs. Thus, during boot we end up with a
kernel crash like following:

	Enabling APIC mode:  Flat.  Using 1 I/O APICs
	BUG: unable to handle kernel NULL pointer dereference at 00000018
	IP: [<c107bdc6>] __irq_domain_alloc_irqs+0xff/0x250

The patch fixes the issue by threating legacy property correctly on non-PC
platforms.

Cc: Jiang Liu <jiang.liu@linux.intel.com>
Cc: Joerg Roedel <joro@8bytes.org>
Cc: David Cohen <david.a.cohen@linux.intel.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
---
 arch/x86/kernel/apic/io_apic.c | 11 ++++++++---
 1 file changed, 8 insertions(+), 3 deletions(-)

diff --git a/arch/x86/kernel/apic/io_apic.c b/arch/x86/kernel/apic/io_apic.c
index fe67a5d..14144d8 100644
--- a/arch/x86/kernel/apic/io_apic.c
+++ b/arch/x86/kernel/apic/io_apic.c
@@ -149,6 +149,11 @@ static inline u32 mp_pin_to_gsi(int ioapic, int pin)
 	return mp_ioapic_gsi_routing(ioapic)->gsi_base + pin;
 }
 
+static inline bool mp_is_legacy_irq(int irq)
+{
+	return irq >= 0 && irq < nr_legacy_irqs();
+}
+
 /*
  * Initialize all legacy IRQs and all pins on the first IOAPIC
  * if we have legacy interrupt controller. Kernel boot option "pirq="
@@ -159,7 +164,7 @@ static inline int mp_init_irq_at_boot(int ioapic, int irq)
 	if (!nr_legacy_irqs())
 		return 0;
 
-	return ioapic == 0 || (irq >= 0 && irq < nr_legacy_irqs());
+	return ioapic == 0 || mp_is_legacy_irq(irq);
 }
 
 static inline struct irq_domain *mp_ioapic_irqdomain(int ioapic)
@@ -960,7 +965,7 @@ static int alloc_irq_from_domain(struct irq_domain *domain, int ioapic, u32 gsi,
 		 */
 		if (!ioapic_initialized || gsi >= nr_legacy_irqs())
 			irq = gsi;
-		legacy = irq >= 0 && irq < nr_legacy_irqs();
+		legacy = mp_is_legacy_irq(irq);
 		break;
 	case IOAPIC_DOMAIN_STRICT:
 		irq = gsi;
@@ -1031,8 +1036,8 @@ static int mp_map_pin_to_irq(u32 gsi, int idx, int ioapic, int pin,
 		return -ENOSYS;
 
 	if (idx >= 0 && test_bit(mp_irqs[idx].srcbus, mp_bus_not_pci)) {
-		legacy = true;
 		irq = mp_irqs[idx].srcbusirq;
+		legacy = mp_is_legacy_irq(irq);
 	}
 
 	mutex_lock(&ioapic_mutex);
-- 
2.1.3