[PATCH v2 1/1] iommu/vt-d: Support asynchronous IOMMU nested capabilities

[Lu Baolu]

Current VT-d implementation supports nested translation only if all
underlying IOMMUs support the nested capability. This is unnecessary
as the upper layer is allowed to create different containers and set
them with different type of iommu backend. The IOMMU driver needs to
guarantee that devices attached to a nested mode iommu_domain should
support nested capabilility.

Signed-off-by: Lu Baolu <baolu.lu@xxxxxxxxxxxxxxx>
---
 drivers/iommu/intel/iommu.c | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

Change log:
v1->v2:
  - Remove unnecessary global capability check

diff --git a/drivers/iommu/intel/iommu.c b/drivers/iommu/intel/iommu.c
index f1742da42478..00c6611ee839 100644
--- a/drivers/iommu/intel/iommu.c
+++ b/drivers/iommu/intel/iommu.c
@@ -4755,6 +4755,13 @@ static int prepare_domain_attach_device(struct iommu_domain *domain,
 	if (!iommu)
 		return -ENODEV;
 
+	if ((dmar_domain->flags & DOMAIN_FLAG_NESTING_MODE) &&
+	    !ecap_nest(iommu->ecap)) {
+		dev_err(dev, "%s: iommu not support nested translation\n",
+			iommu->name);
+		return -EINVAL;
+	}
+
 	/* check if this iommu agaw is sufficient for max mapped address */
 	addr_width = agaw_to_width(iommu->agaw);
 	if (addr_width > cap_mgaw(iommu->cap))
@@ -5455,7 +5462,7 @@ intel_iommu_enable_nesting(struct iommu_domain *domain)
 	int ret = -ENODEV;
 
 	spin_lock_irqsave(&device_domain_lock, flags);
-	if (nested_mode_support() && list_empty(&dmar_domain->devices)) {
+	if (list_empty(&dmar_domain->devices)) {
 		dmar_domain->flags |= DOMAIN_FLAG_NESTING_MODE;
 		dmar_domain->flags &= ~DOMAIN_FLAG_USE_FIRST_LEVEL;
 		ret = 0;
-- 
2.25.1