RDMA/usnic: Stop using iommu_present()

Even if an IOMMU might be present for some PCI segment in the system,
that doesn't necessarily mean it provides translation for the device(s)
we care about. Replace iommu_present() with a more appropriate check at
probe time, and garbage-collect the resulting empty init function.

Link: https://lore.kernel.org/r/f707b4248e1d33b6d2c7f1d7c94febb802cf9890.1649161199.git.robin.murphy@arm.comSigned-off-by: Robin Murphy <robin.murphy@arm.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>

drivers/infiniband/hw/usnic/usnic_ib_main.c

@@ -534,6 +534,11 @@ static int usnic_ib_pci_probe(struct pci_dev *pdev,
 	struct usnic_ib_vf *vf;
 	enum usnic_vnic_res_type res_type;
 
+	if (!device_iommu_mapped(&pdev->dev)) {
+		usnic_err("IOMMU required but not present or enabled.  USNIC QPs will not function w/o enabling IOMMU\n");
+		return -EPERM;
+	}
+
 	vf = kzalloc(sizeof(*vf), GFP_KERNEL);
 	if (!vf)
 		return -ENOMEM;
@@ -642,12 +647,6 @@ static int __init usnic_ib_init(void)
 
 	printk_once(KERN_INFO "%s", usnic_version);
 
-	err = usnic_uiom_init(DRV_NAME);
-	if (err) {
-		usnic_err("Unable to initialize umem with err %d\n", err);
-		return err;
-	}
-
 	err = pci_register_driver(&usnic_ib_pci_driver);
 	if (err) {
 		usnic_err("Unable to register with PCI\n");

drivers/infiniband/hw/usnic/usnic_uiom.c

@@ -556,13 +556,3 @@ void usnic_uiom_free_dev_list(struct device **devs)
 {
 	kfree(devs);
 }
-
-int usnic_uiom_init(char *drv_name)
-{
-	if (!iommu_present(&pci_bus_type)) {
-		usnic_err("IOMMU required but not present or enabled.  USNIC QPs will not function w/o enabling IOMMU\n");
-		return -EPERM;
-	}
-
-	return 0;
-}

drivers/infiniband/hw/usnic/usnic_uiom.h

@@ -91,5 +91,4 @@ struct usnic_uiom_reg *usnic_uiom_reg_get(struct usnic_uiom_pd *pd,
 						unsigned long addr, size_t size,
 						int access, int dmasync);
 void usnic_uiom_reg_release(struct usnic_uiom_reg *uiomr);
-int usnic_uiom_init(char *drv_name);
 #endif /* USNIC_UIOM_H_ */