[PATCH] iommu/vt-d: Try info->iommu in device_to_iommu()

[Nicolin Chen]

Local boot test and VFIO sanity test show that info->iommu can be
used in device_to_iommu() as a fast path. So this patch adds it.

Signed-off-by: Nicolin Chen <nicolinc@xxxxxxxxxx>
---
 drivers/iommu/intel/iommu.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/drivers/iommu/intel/iommu.c b/drivers/iommu/intel/iommu.c
index 2990f80c5e08..412fca5ab9cd 100644
--- a/drivers/iommu/intel/iommu.c
+++ b/drivers/iommu/intel/iommu.c
@@ -777,6 +777,7 @@ static bool iommu_is_dummy(struct intel_iommu *iommu, struct device *dev)
 struct intel_iommu *device_to_iommu(struct device *dev, u8 *bus, u8 *devfn)
 {
 	struct dmar_drhd_unit *drhd = NULL;
+	struct device_domain_info *info;
 	struct pci_dev *pdev = NULL;
 	struct intel_iommu *iommu;
 	struct device *tmp;
@@ -786,6 +787,10 @@ struct intel_iommu *device_to_iommu(struct device *dev, u8 *bus, u8 *devfn)
 	if (!dev)
 		return NULL;
 
+	info = dev_iommu_priv_get(dev);
+	if (info)
+		return info->iommu;
+
 	if (dev_is_pci(dev)) {
 		struct pci_dev *pf_pdev;
 
-- 
2.17.1