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>

arch/x86/kernel/amd_iommu.c

@@ -1924,6 +1924,12 @@ static phys_addr_t amd_iommu_iova_to_phys(struct iommu_domain *dom,
 	return paddr;
 }
 
+static int amd_iommu_domain_has_cap(struct iommu_domain *domain,
+				    unsigned long cap)
+{
+	return 0;
+}
+
 static struct iommu_ops amd_iommu_ops = {
 	.domain_init = amd_iommu_domain_init,
 	.domain_destroy = amd_iommu_domain_destroy,
@@ -1932,5 +1938,6 @@ static struct iommu_ops amd_iommu_ops = {
 	.map = amd_iommu_map_range,
 	.unmap = amd_iommu_unmap_range,
 	.iova_to_phys = amd_iommu_iova_to_phys,
+	.domain_has_cap = amd_iommu_domain_has_cap,
 };
 

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);

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)

include/linux/iommu.h

@@ -28,6 +28,8 @@ struct iommu_domain {
 	void *priv;
 };
 
+#define IOMMU_CAP_CACHE_COHERENCY	0x1
+
 struct iommu_ops {
 	int (*domain_init)(struct iommu_domain *domain);
 	void (*domain_destroy)(struct iommu_domain *domain);
@@ -39,6 +41,8 @@ struct iommu_ops {
 		      size_t size);
 	phys_addr_t (*iova_to_phys)(struct iommu_domain *domain,
 				    unsigned long iova);
+	int (*domain_has_cap)(struct iommu_domain *domain,
+			      unsigned long cap);
 };
 
 #ifdef CONFIG_IOMMU_API
@@ -57,6 +61,8 @@ extern void iommu_unmap_range(struct iommu_domain *domain, unsigned long iova,
 			      size_t size);
 extern phys_addr_t iommu_iova_to_phys(struct iommu_domain *domain,
 				      unsigned long iova);
+extern int iommu_domain_has_cap(struct iommu_domain *domain,
+				unsigned long cap);
 
 #else /* CONFIG_IOMMU_API */
 
@@ -107,6 +113,12 @@ static inline phys_addr_t iommu_iova_to_phys(struct iommu_domain *domain,
 	return 0;
 }
 
+static inline int domain_has_cap(struct iommu_domain *domain,
+				 unsigned long cap)
+{
+	return 0;
+}
+
 #endif /* CONFIG_IOMMU_API */
 
 #endif /* __LINUX_IOMMU_H */