[Patch v8 02/10] iommu/smmu: Report empty domain nesting info

[Liu Yi L <yi.l.liu@intel.com>]

This patch is added as instead of returning a boolean for DOMAIN_ATTR_NESTING,
iommu_domain_get_attr() should return an iommu_nesting_info handle. For
now, return an empty nesting info struct for now as true nesting is not
yet supported by the SMMUs.

Note: this patch just ensure no compiling issue, to be functional ready
fro ARM platform, needs to apply patches from Vivek Gautam in below link.

https://lore.kernel.org/linux-iommu/20210212105859.8445-1-vivek.gautam@arm.com/

Cc: Will Deacon <will@kernel.org>
Cc: Robin Murphy <robin.murphy@arm.com>
Cc: Eric Auger <eric.auger@redhat.com>
Cc: Jean-Philippe Brucker <jean-philippe@linaro.org>
Suggested-by: Jean-Philippe Brucker <jean-philippe@linaro.org>
Signed-off-by: Liu Yi L <yi.l.liu@intel.com>
Signed-off-by: Jacob Pan <jacob.jun.pan@linux.intel.com>
Reviewed-by: Eric Auger <eric.auger@redhat.com>
---
v5 -> v6:
*) add review-by from Eric Auger.

v4 -> v5:
*) address comments from Eric Auger.
---
 drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c | 29 +++++++++++++++++++--
 drivers/iommu/arm/arm-smmu/arm-smmu.c       | 29 +++++++++++++++++++--
 2 files changed, 54 insertions(+), 4 deletions(-)

diff --git a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
index 8594b4a83043..99ea3ee35826 100644
--- a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
+++ b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
@@ -2449,6 +2449,32 @@ static struct iommu_group *arm_smmu_device_group(struct device *dev)
 	return group;
 }
 
+static int arm_smmu_domain_nesting_info(struct arm_smmu_domain *smmu_domain,
+					void *data)
+{
+	struct iommu_nesting_info *info = (struct iommu_nesting_info *)data;
+	unsigned int size;
+
+	if (!info || smmu_domain->stage != ARM_SMMU_DOMAIN_NESTED)
+		return -ENODEV;
+
+	size = sizeof(struct iommu_nesting_info);
+
+	/*
+	 * if provided buffer size is smaller than expected, should
+	 * return 0 and also the expected buffer size to caller.
+	 */
+	if (info->argsz < size) {
+		info->argsz = size;
+		return 0;
+	}
+
+	/* report an empty iommu_nesting_info for now */
+	memset(info, 0x0, size);
+	info->argsz = size;
+	return 0;
+}
+
 static int arm_smmu_domain_get_attr(struct iommu_domain *domain,
 				    enum iommu_attr attr, void *data)
 {
@@ -2458,8 +2484,7 @@ static int arm_smmu_domain_get_attr(struct iommu_domain *domain,
 	case IOMMU_DOMAIN_UNMANAGED:
 		switch (attr) {
 		case DOMAIN_ATTR_NESTING:
-			*(int *)data = (smmu_domain->stage == ARM_SMMU_DOMAIN_NESTED);
-			return 0;
+			return arm_smmu_domain_nesting_info(smmu_domain, data);
 		default:
 			return -ENODEV;
 		}
diff --git a/drivers/iommu/arm/arm-smmu/arm-smmu.c b/drivers/iommu/arm/arm-smmu/arm-smmu.c
index d8c6bfde6a61..d874c580ea80 100644
--- a/drivers/iommu/arm/arm-smmu/arm-smmu.c
+++ b/drivers/iommu/arm/arm-smmu/arm-smmu.c
@@ -1481,6 +1481,32 @@ static struct iommu_group *arm_smmu_device_group(struct device *dev)
 	return group;
 }
 
+static int arm_smmu_domain_nesting_info(struct arm_smmu_domain *smmu_domain,
+					void *data)
+{
+	struct iommu_nesting_info *info = (struct iommu_nesting_info *)data;
+	unsigned int size;
+
+	if (!info || smmu_domain->stage != ARM_SMMU_DOMAIN_NESTED)
+		return -ENODEV;
+
+	size = sizeof(struct iommu_nesting_info);
+
+	/*
+	 * if provided buffer size is smaller than expected, should
+	 * return 0 and also the expected buffer size to caller.
+	 */
+	if (info->argsz < size) {
+		info->argsz = size;
+		return 0;
+	}
+
+	/* report an empty iommu_nesting_info for now */
+	memset(info, 0x0, size);
+	info->argsz = size;
+	return 0;
+}
+
 static int arm_smmu_domain_get_attr(struct iommu_domain *domain,
 				    enum iommu_attr attr, void *data)
 {
@@ -1490,8 +1516,7 @@ static int arm_smmu_domain_get_attr(struct iommu_domain *domain,
 	case IOMMU_DOMAIN_UNMANAGED:
 		switch (attr) {
 		case DOMAIN_ATTR_NESTING:
-			*(int *)data = (smmu_domain->stage == ARM_SMMU_DOMAIN_NESTED);
-			return 0;
+			return arm_smmu_domain_nesting_info(smmu_domain, data);
 		case DOMAIN_ATTR_IO_PGTABLE_CFG: {
 			struct io_pgtable_domain_attr *pgtbl_cfg = data;
 			*pgtbl_cfg = smmu_domain->pgtbl_cfg;
-- 
2.25.1