[ 062/108] irq_remap: disable IRQ remapping if any IOAPIC lacks an IOMMU

Ben Hutchings
2012-10-07T23:34:36Z

From: Seth Forshee <seth.forshee@canonical.com>

commit 32ab31e01e2def6f48294d872d9bb42573aae00f upstream.

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>
[bwh: Backported to 3.2: adjust filename]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---
drivers/iommu/intr_remapping.c | 18 +++++++++++++-----
1 file changed, 13 insertions(+), 5 deletions(-)

--- a/drivers/iommu/intr_remapping.c
+++ b/drivers/iommu/intr_remapping.c
@@ -752,6 +752,7 @@ 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;
@@ -764,13 +765,20 @@ 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)