iommu: Add domain_has_cap iommu_ops

This iommu_op can tell if domain have a specific capability, like snooping
control for Intel IOMMU, which can be used by other components of kernel to
adjust the behaviour.

Signed-off-by: Sheng Yang <sheng@linux.intel.com>
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>

2 files changed, 19 insertions, 0 deletions

diff --git a/drivers/base/iommu.c b/drivers/base/iommu.c
index 5e039d4f877c..c314f144825f 100644
--- a/drivers/base/iommu.c
+++ b/drivers/base/iommu.c
@@ -98,3 +98,10 @@ phys_addr_t iommu_iova_to_phys(struct iommu_domain *domain,
         return iommu_ops->iova_to_phys(domain, iova);
 }
 EXPORT_SYMBOL_GPL(iommu_iova_to_phys);
+
+int iommu_domain_has_cap(struct iommu_domain *domain,
+                         unsigned long cap)
+{
+        return iommu_ops->domain_has_cap(domain, cap);
+}
+EXPORT_SYMBOL_GPL(iommu_domain_has_cap);
diff --git a/drivers/pci/intel-iommu.c b/drivers/pci/intel-iommu.c
index be999ff025af..3778ab149baf 100644
--- a/drivers/pci/intel-iommu.c
+++ b/drivers/pci/intel-iommu.c
@@ -3158,6 +3158,17 @@ static phys_addr_t intel_iommu_iova_to_phys(struct iommu_domain *domain,
         return phys;
 }
 
+static int intel_iommu_domain_has_cap(struct iommu_domain *domain,
+                                      unsigned long cap)
+{
+        struct dmar_domain *dmar_domain = domain->priv;
+
+        if (cap == IOMMU_CAP_CACHE_COHERENCY)
+                return dmar_domain->iommu_snooping;
+
+        return 0;
+}
+
 static struct iommu_ops intel_iommu_ops = {
         .domain_init    = intel_iommu_domain_init,
         .domain_destroy = intel_iommu_domain_destroy,
@@ -3166,6 +3177,7 @@ static struct iommu_ops intel_iommu_ops = {
         .map            = intel_iommu_map_range,
         .unmap          = intel_iommu_unmap_range,
         .iova_to_phys   = intel_iommu_iova_to_phys,
+        .domain_has_cap = intel_iommu_domain_has_cap,
 };
 
 static void __devinit quirk_iommu_rwbf(struct pci_dev *dev)