[PATCH] iommu/vt-d: Enhance capability check for nested parent domain allocation

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

This adds the scalable mode check before allocating the nested parent domain
as checking nested capability is not enough. User may turn off scalable mode
which also means no nested support even if the hardware supports it.

Fixes: c97d1b20d383 ("iommu/vt-d: Add domain_alloc_user op")
Signed-off-by: Yi Liu <yi.l.liu@intel.com>
---
v1: Based on Joao's dirty page tracking v6 https://github.com/jpemartins/linux/commits/iommufd-v6
---
 drivers/iommu/intel/iommu.c | 2 +-
 drivers/iommu/intel/iommu.h | 2 ++
 2 files changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/iommu/intel/iommu.c b/drivers/iommu/intel/iommu.c
index eb92a201cc0b..65f46f1347e6 100644
--- a/drivers/iommu/intel/iommu.c
+++ b/drivers/iommu/intel/iommu.c
@@ -4090,7 +4090,7 @@ intel_iommu_domain_alloc_user(struct device *dev, u32 flags)
 	if (!iommu)
 		return ERR_PTR(-ENODEV);
 
-	if ((flags & IOMMU_HWPT_ALLOC_NEST_PARENT) && !ecap_nest(iommu->ecap))
+	if ((flags & IOMMU_HWPT_ALLOC_NEST_PARENT) && !nested_supported(iommu))
 		return ERR_PTR(-EOPNOTSUPP);
 
 	dirty_tracking = (flags & IOMMU_HWPT_ALLOC_DIRTY_TRACKING);
diff --git a/drivers/iommu/intel/iommu.h b/drivers/iommu/intel/iommu.h
index 3bb569146229..cc7301579773 100644
--- a/drivers/iommu/intel/iommu.h
+++ b/drivers/iommu/intel/iommu.h
@@ -544,6 +544,8 @@ enum {
 				 ecap_pasid((iommu)->ecap))
 #define ssads_supported(iommu) (sm_supported(iommu) &&                 \
 				ecap_slads((iommu)->ecap))
+#define nested_supported(iommu)	(sm_supported(iommu) &&			\
+				 ecap_nest((iommu)->ecap))
 
 struct pasid_entry;
 struct pasid_state_entry;
-- 
2.34.1