iommu/vt-d: Remove identity mappings from si_domain

As the driver has enforced DMA domains for devices managed by an IOMMU
hardware that doesn't support passthrough translation mode, there is no
need for static identity mappings in the si_domain. Remove the identity
mapping code to avoid dead code.

Signed-off-by: Lu Baolu <baolu.lu@linux.intel.com>
Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
Reviewed-by: Kevin Tian <kevin.tian@intel.com>
Link: https://lore.kernel.org/r/20240809055431.36513-3-baolu.lu@linux.intel.com
Signed-off-by: Joerg Roedel <jroedel@suse.de>

drivers/iommu/intel/iommu.c

@@ -167,14 +167,7 @@ static void device_rbtree_remove(struct device_domain_info *info)
 	spin_unlock_irqrestore(&iommu->device_rbtree_lock, flags);
 }
 
-/*
- * This domain is a statically identity mapping domain.
- *	1. This domain creats a static 1:1 mapping to all usable memory.
- * 	2. It maps to each iommu if successful.
- *	3. Each iommu mapps to this domain if successful.
- */
 static struct dmar_domain *si_domain;
-static int hw_pass_through = 1;
 
 struct dmar_rmrr_unit {
 	struct list_head list;		/* list of rmrr units	*/
@@ -1647,7 +1640,7 @@ static int domain_context_mapping_one(struct dmar_domain *domain,
 	struct context_entry *context;
 	int agaw, ret;
 
-	if (hw_pass_through && domain_type_is_si(domain))
+	if (domain_type_is_si(domain))
 		translation = CONTEXT_TT_PASS_THROUGH;
 
 	pr_debug("Set context mapping for %02x:%02x.%d\n",
@@ -1998,29 +1991,10 @@ static bool dev_is_real_dma_subdevice(struct device *dev)
 	       pci_real_dma_dev(to_pci_dev(dev)) != to_pci_dev(dev);
 }
 
-static int iommu_domain_identity_map(struct dmar_domain *domain,
-				     unsigned long first_vpfn,
-				     unsigned long last_vpfn)
-{
-	/*
-	 * RMRR range might have overlap with physical memory range,
-	 * clear it first
-	 */
-	dma_pte_clear_range(domain, first_vpfn, last_vpfn);
-
-	return __domain_mapping(domain, first_vpfn,
-				first_vpfn, last_vpfn - first_vpfn + 1,
-				DMA_PTE_READ|DMA_PTE_WRITE, GFP_KERNEL);
-}
-
 static int md_domain_init(struct dmar_domain *domain, int guest_width);
 
-static int __init si_domain_init(int hw)
+static int __init si_domain_init(void)
 {
-	struct dmar_rmrr_unit *rmrr;
-	struct device *dev;
-	int i, nid, ret;
-
 	si_domain = alloc_domain(IOMMU_DOMAIN_IDENTITY);
 	if (!si_domain)
 		return -EFAULT;
@@ -2031,44 +2005,6 @@ static int __init si_domain_init(int hw)
 		return -EFAULT;
 	}
 
-	if (hw)
-		return 0;
-
-	for_each_online_node(nid) {
-		unsigned long start_pfn, end_pfn;
-		int i;
-
-		for_each_mem_pfn_range(i, nid, &start_pfn, &end_pfn, NULL) {
-			ret = iommu_domain_identity_map(si_domain,
-					mm_to_dma_pfn_start(start_pfn),
-					mm_to_dma_pfn_end(end_pfn-1));
-			if (ret)
-				return ret;
-		}
-	}
-
-	/*
-	 * Identity map the RMRRs so that devices with RMRRs could also use
-	 * the si_domain.
-	 */
-	for_each_rmrr_units(rmrr) {
-		for_each_active_dev_scope(rmrr->devices, rmrr->devices_cnt,
-					  i, dev) {
-			unsigned long long start = rmrr->base_address;
-			unsigned long long end = rmrr->end_address;
-
-			if (WARN_ON(end < start ||
-				    end >> agaw_to_width(si_domain->agaw)))
-				continue;
-
-			ret = iommu_domain_identity_map(si_domain,
-					mm_to_dma_pfn_start(start >> PAGE_SHIFT),
-					mm_to_dma_pfn_end(end >> PAGE_SHIFT));
-			if (ret)
-				return ret;
-		}
-	}
-
 	return 0;
 }
 
@@ -2094,7 +2030,7 @@ static int dmar_domain_attach_device(struct dmar_domain *domain,
 
 	if (!sm_supported(iommu))
 		ret = domain_context_mapping(domain, dev);
-	else if (hw_pass_through && domain_type_is_si(domain))
+	else if (domain_type_is_si(domain))
 		ret = intel_pasid_setup_pass_through(iommu, dev, IOMMU_NO_PASID);
 	else if (domain->use_first_level)
 		ret = domain_setup_first_level(iommu, domain, dev, IOMMU_NO_PASID);
@@ -2449,8 +2385,6 @@ static int __init init_dmars(void)
 			}
 		}
 
-		if (!ecap_pass_through(iommu->ecap))
-			hw_pass_through = 0;
 		intel_svm_check(iommu);
 	}
 
@@ -2466,7 +2400,7 @@ static int __init init_dmars(void)
 
 	check_tylersburg_isoch();
 
-	ret = si_domain_init(hw_pass_through);
+	ret = si_domain_init();
 	if (ret)
 		goto free_iommu;
 
@@ -2893,12 +2827,6 @@ static int intel_iommu_add(struct dmar_drhd_unit *dmaru)
 	if (ret)
 		goto out;
 
-	if (hw_pass_through && !ecap_pass_through(iommu->ecap)) {
-		pr_warn("%s: Doesn't support hardware pass through.\n",
-			iommu->name);
-		return -ENXIO;
-	}
-
 	sp = domain_update_iommu_superpage(NULL, iommu) - 1;
 	if (sp >= 0 && !(cap_super_page_val(iommu->cap) & (1 << sp))) {
 		pr_warn("%s: Doesn't support large page.\n",
@@ -3149,43 +3077,6 @@ int dmar_iommu_notify_scope_dev(struct dmar_pci_notify_info *info)
 	return 0;
 }
 
-static int intel_iommu_memory_notifier(struct notifier_block *nb,
-				       unsigned long val, void *v)
-{
-	struct memory_notify *mhp = v;
-	unsigned long start_vpfn = mm_to_dma_pfn_start(mhp->start_pfn);
-	unsigned long last_vpfn = mm_to_dma_pfn_end(mhp->start_pfn +
-			mhp->nr_pages - 1);
-
-	switch (val) {
-	case MEM_GOING_ONLINE:
-		if (iommu_domain_identity_map(si_domain,
-					      start_vpfn, last_vpfn)) {
-			pr_warn("Failed to build identity map for [%lx-%lx]\n",
-				start_vpfn, last_vpfn);
-			return NOTIFY_BAD;
-		}
-		break;
-
-	case MEM_OFFLINE:
-	case MEM_CANCEL_ONLINE:
-		{
-			LIST_HEAD(freelist);
-
-			domain_unmap(si_domain, start_vpfn, last_vpfn, &freelist);
-			iommu_put_pages_list(&freelist);
-		}
-		break;
-	}
-
-	return NOTIFY_OK;
-}
-
-static struct notifier_block intel_iommu_memory_nb = {
-	.notifier_call = intel_iommu_memory_notifier,
-	.priority = 0
-};
-
 static void intel_disable_iommus(void)
 {
 	struct intel_iommu *iommu = NULL;
@@ -3482,12 +3373,7 @@ int __init intel_iommu_init(void)
 
 		iommu_pmu_register(iommu);
 	}
-	up_read(&dmar_global_lock);
-
-	if (si_domain && !hw_pass_through)
-		register_memory_notifier(&intel_iommu_memory_nb);
 
-	down_read(&dmar_global_lock);
 	if (probe_acpi_namespace_devices())
 		pr_warn("ACPI name space devices didn't probe correctly\n");