[PATCH] irq_remap: disable IRQ remapping if any IOAPIC lacks an IOMMU

[Seth Forshee]

The ACPI tables in the Macbook Air 5,1 define a single IOAPIC with id 2,
but the only remapping unit described in the DMAR table matches id 0.
Interrupt remapping fails as a result, and the kernel panics with the
message "timer doesn't work through Interrupt-remapped IO-APIC."

To fix this, check each IOAPIC for a corresponding IOMMU. If an IOMMU is
not found, do not allow IRQ remapping to be enabled.

Signed-off-by: Seth Forshee <seth.forshee@xxxxxxxxxxxxx>
---
 drivers/iommu/intel_irq_remapping.c |   11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/drivers/iommu/intel_irq_remapping.c b/drivers/iommu/intel_irq_remapping.c
index e0b18f3..ce2c0c6 100644
--- a/drivers/iommu/intel_irq_remapping.c
+++ b/drivers/iommu/intel_irq_remapping.c
@@ -526,6 +526,7 @@ static int __init intel_irq_remapping_supported(void)
 static int __init intel_enable_irq_remapping(void)
 {
 	struct dmar_drhd_unit *drhd;
+	int ioapic_idx;
 	int setup = 0;
 	int eim = 0;
 
@@ -534,6 +535,16 @@ static int __init intel_enable_irq_remapping(void)
 		return -1;
 	}
 
+	for (ioapic_idx = 0; ioapic_idx < nr_ioapics; ioapic_idx++) {
+		int ioapic_id = mpc_ioapic_id(ioapic_idx);
+		if (!map_ioapic_to_ir(ioapic_id)) {
+			pr_info("ioapic %d has no mapping iommu, "
+				"interrupt remapping will be disabled\n",
+				ioapic_id);
+			return -1;
+		}
+	}
+
 	if (x2apic_supported()) {
 		eim = !dmar_x2apic_optout();
 		WARN(!eim, KERN_WARNING
-- 
1.7.9.5

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