irq_remap: disable IRQ remapping if any IOAPIC lacks an IOMMU

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.

v2: Move check to parse_ioapics_under_ir(), raise log level to KERN_ERR,
    and add FW_BUG to the log message
v3: Skip check if IOMMU doesn't support interrupt remapping and remove
    existing check that the IOMMU count equals the IOAPIC count

Acked-by: Suresh Siddha <suresh.b.siddha@intel.com>
Signed-off-by: Seth Forshee <seth.forshee@canonical.com>
Acked-by: Yinghai Lu <yinghai@kernel.org>
Signed-off-by: Joerg Roedel <joerg.roedel@amd.com>

1 files changed, 13 insertions, 5 deletions

diff --git a/drivers/iommu/intel_irq_remapping.c b/drivers/iommu/intel_irq_remapping.c
index e0b18f3ae9a8..af8904de1d44 100644
--- a/drivers/iommu/intel_irq_remapping.c
+++ b/drivers/iommu/intel_irq_remapping.c
@@ -736,6 +736,7 @@ int __init parse_ioapics_under_ir(void)
 {
         struct dmar_drhd_unit *drhd;
         int ir_supported = 0;
+        int ioapic_idx;
 
         for_each_drhd_unit(drhd) {
                 struct intel_iommu *iommu = drhd->iommu;
@@ -748,13 +749,20 @@ int __init parse_ioapics_under_ir(void)
                 }
         }
 
-        if (ir_supported && ir_ioapic_num != nr_ioapics) {
-                printk(KERN_WARNING
-                       "Not all IO-APIC's listed under remapping hardware\n");
-                return -1;
+        if (!ir_supported)
+                return 0;
+
+        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_err(FW_BUG "ioapic %d has no mapping iommu, "
+                               "interrupt remapping will be disabled\n",
+                               ioapic_id);
+                        return -1;
+                }
         }
 
-        return ir_supported;
+        return 1;
 }
 
 int __init ir_dev_scope_init(void)