iommu/core: let drivers know if an iommu fault handler isn't installed

Make report_iommu_fault() return -ENOSYS whenever an iommu fault
handler isn't installed, so IOMMU drivers can then do their own
platform-specific default behavior if they wanted.

Fault handlers can still return -ENOSYS in case they want to elicit the
default behavior of the IOMMU drivers.

Signed-off-by: Ohad Ben-Cohen <ohad@wizery.com>
Signed-off-by: Joerg Roedel <joerg.roedel@amd.com>

1 files changed, 5 insertions, 1 deletions

diff --git a/include/linux/iommu.h b/include/linux/iommu.h
index d084e8777e0e..ddad0ae0a433 100644
--- a/include/linux/iommu.h
+++ b/include/linux/iommu.h
@@ -98,11 +98,15 @@ extern void iommu_set_fault_handler(struct iommu_domain *domain,
  * Returns 0 on success and an appropriate error code otherwise (if dynamic
  * PTE/TLB loading will one day be supported, implementations will be able
  * to tell whether it succeeded or not according to this return value).
+ *
+ * Specifically, -ENOSYS is returned if a fault handler isn't installed
+ * (though fault handlers can also return -ENOSYS, in case they want to
+ * elicit the default behavior of the IOMMU drivers).
  */
 static inline int report_iommu_fault(struct iommu_domain *domain,
                 struct device *dev, unsigned long iova, int flags)
 {
-        int ret = 0;
+        int ret = -ENOSYS;
 
         /*
          * if upper layers showed interest and installed a fault handler,