[PATCH v12 03/10] iommu: Separate IOMMU_DEV_FEAT_IOPF from IOMMU_DEV_FEAT_SVA

[Jean-Philippe Brucker]

Some devices manage I/O Page Faults (IOPF) themselves instead of relying
on PCIe PRI or Arm SMMU stall. Allow their drivers to enable SVA without
mandating IOMMU-managed IOPF. The other device drivers now need to first
enable IOMMU_DEV_FEAT_IOPF before enabling IOMMU_DEV_FEAT_SVA. Enabling
IOMMU_DEV_FEAT_IOPF on its own doesn't have any effect visible to the
device driver, it is used in combination with other features.

Signed-off-by: Jean-Philippe Brucker <jean-philippe at linaro.org>
---
Cc: Arnd Bergmann <arnd at arndb.de>
Cc: David Woodhouse <dwmw2 at infradead.org>
Cc: Greg Kroah-Hartman <gregkh at linuxfoundation.org>
Cc: Joerg Roedel <joro at 8bytes.org>
Cc: Lu Baolu <baolu.lu at linux.intel.com>
Cc: Will Deacon <will at kernel.org>
Cc: Zhangfei Gao <zhangfei.gao at linaro.org>
Cc: Zhou Wang <wangzhou1 at hisilicon.com>
---
 include/linux/iommu.h | 20 +++++++++++++++++---
 1 file changed, 17 insertions(+), 3 deletions(-)

diff --git a/include/linux/iommu.h b/include/linux/iommu.h
index b7ea11fc1a93..00348e4c3c26 100644
--- a/include/linux/iommu.h
+++ b/include/linux/iommu.h
@@ -156,10 +156,24 @@ struct iommu_resv_region {
 	enum iommu_resv_type	type;
 };
 
-/* Per device IOMMU features */
+/**
+ * enum iommu_dev_features - Per device IOMMU features
+ * @IOMMU_DEV_FEAT_AUX: Auxiliary domain feature
+ * @IOMMU_DEV_FEAT_SVA: Shared Virtual Addresses
+ * @IOMMU_DEV_FEAT_IOPF: I/O Page Faults such as PRI or Stall. Generally
+ *			 enabling %IOMMU_DEV_FEAT_SVA requires
+ *			 %IOMMU_DEV_FEAT_IOPF, but some devices manage I/O Page
+ *			 Faults themselves instead of relying on the IOMMU. When
+ *			 supported, this feature must be enabled before and
+ *			 disabled after %IOMMU_DEV_FEAT_SVA.
+ *
+ * Device drivers query whether a feature is supported using
+ * iommu_dev_has_feature(), and enable it using iommu_dev_enable_feature().
+ */
 enum iommu_dev_features {
-	IOMMU_DEV_FEAT_AUX,	/* Aux-domain feature */
-	IOMMU_DEV_FEAT_SVA,	/* Shared Virtual Addresses */
+	IOMMU_DEV_FEAT_AUX,
+	IOMMU_DEV_FEAT_SVA,
+	IOMMU_DEV_FEAT_IOPF,
 };
 
 #define IOMMU_PASID_INVALID	(-1U)
-- 
2.30.0