iommu/vt-d: Only call dmar_acpi_dev_scope_init() if DRHD units present

As pointed out by Jörg and fixed in commit 11f1a7768 ("iommu/vt-d: Check
for NULL pointer in dmar_acpi_dev_scope_init(), this code path can
bizarrely get exercised even on AMD IOMMU systems with IRQ remapping
enabled.

In addition to the defensive check for NULL which Jörg added, let's also
just avoid calling the function at all if there aren't an Intel IOMMU
units in the system.

Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>

diff --git a/drivers/iommu/dmar.c b/drivers/iommu/dmar.c
index e531a2b07207ef7b01c233370352aa68266879c3..142650e8297903e6904fd7ec32d57b6f9e784dc3 100644 (file)
--- a/drivers/iommu/dmar.c
+++ b/drivers/iommu/dmar.c
@@ -698,13 +698,13 @@ int __init dmar_dev_scope_init(void)
        if (dmar_dev_scope_status != 1)
                return dmar_dev_scope_status;
 
-       dmar_acpi_dev_scope_init();
-
        if (list_empty(&dmar_drhd_units)) {
                dmar_dev_scope_status = -ENODEV;
        } else {
                dmar_dev_scope_status = 0;
 
+               dmar_acpi_dev_scope_init();
+
                for_each_pci_dev(dev) {
                        if (dev->is_virtfn)
                                continue;