[PATCH 1/1] Revert "iommu/vt-d: Fix possible recursive locking in intel_iommu_init()"

[Lu Baolu]

This reverts commit 9cd4f1434479f1ac25c440c421fbf52069079914.

Some issues were reported on the original commit. Some thunderbolt devices
don't work anymore due to the following DMA fault.

DMAR: DRHD: handling fault status reg 2
DMAR: [INTR-REMAP] Request device [09:00.0] fault index 0x8080
      [fault reason 0x25]
      Blocked a compatibility format interrupt request

Bring it back for now to avoid functional regression.

Fixes: 9cd4f1434479f ("iommu/vt-d: Fix possible recursive locking in intel_iommu_init()")
Link: https://lore.kernel.org/linux-iommu/485A6EA5-6D58-42EA-B298-8571E97422DE@xxxxxxxxxxxxxxxxx/
Link: https://bugzilla.kernel.org/show_bug.cgi?id=216497
Cc: Mika Westerberg <mika.westerberg@xxxxxxxxxxxxxxx>
Reported-and-tested-by: George Hilliard <thirtythreeforty@xxxxxxxxx>
Signed-off-by: Lu Baolu <baolu.lu@xxxxxxxxxxxxxxx>
---
 include/linux/dmar.h        |  4 +---
 drivers/iommu/intel/dmar.c  |  7 -------
 drivers/iommu/intel/iommu.c | 27 +++++++++++++++++++++++++--
 3 files changed, 26 insertions(+), 12 deletions(-)

diff --git a/include/linux/dmar.h b/include/linux/dmar.h
index 8917a32173c4..d81a51978d01 100644
--- a/include/linux/dmar.h
+++ b/include/linux/dmar.h
@@ -65,7 +65,6 @@ struct dmar_pci_notify_info {
 
 extern struct rw_semaphore dmar_global_lock;
 extern struct list_head dmar_drhd_units;
-extern int intel_iommu_enabled;
 
 #define for_each_drhd_unit(drhd)					\
 	list_for_each_entry_rcu(drhd, &dmar_drhd_units, list,		\
@@ -89,8 +88,7 @@ extern int intel_iommu_enabled;
 static inline bool dmar_rcu_check(void)
 {
 	return rwsem_is_locked(&dmar_global_lock) ||
-	       system_state == SYSTEM_BOOTING ||
-	       (IS_ENABLED(CONFIG_INTEL_IOMMU) && !intel_iommu_enabled);
+	       system_state == SYSTEM_BOOTING;
 }
 
 #define	dmar_rcu_dereference(p)	rcu_dereference_check((p), dmar_rcu_check())
diff --git a/drivers/iommu/intel/dmar.c b/drivers/iommu/intel/dmar.c
index 04f7991734a9..3528058d253e 100644
--- a/drivers/iommu/intel/dmar.c
+++ b/drivers/iommu/intel/dmar.c
@@ -2356,13 +2356,6 @@ static int dmar_device_hotplug(acpi_handle handle, bool insert)
 	if (!dmar_in_use())
 		return 0;
 
-	/*
-	 * It's unlikely that any I/O board is hot added before the IOMMU
-	 * subsystem is initialized.
-	 */
-	if (IS_ENABLED(CONFIG_INTEL_IOMMU) && !intel_iommu_enabled)
-		return -EOPNOTSUPP;
-
 	if (dmar_detect_dsm(handle, DMAR_DSM_FUNC_DRHD)) {
 		tmp = handle;
 	} else {
diff --git a/drivers/iommu/intel/iommu.c b/drivers/iommu/intel/iommu.c
index c20f3e060bac..5bab71a05830 100644
--- a/drivers/iommu/intel/iommu.c
+++ b/drivers/iommu/intel/iommu.c
@@ -3029,7 +3029,13 @@ static int __init init_dmars(void)
 
 #ifdef CONFIG_INTEL_IOMMU_SVM
 		if (pasid_supported(iommu) && ecap_prs(iommu->ecap)) {
+			/*
+			 * Call dmar_alloc_hwirq() with dmar_global_lock held,
+			 * could cause possible lock race condition.
+			 */
+			up_write(&dmar_global_lock);
 			ret = intel_svm_enable_prq(iommu);
+			down_write(&dmar_global_lock);
 			if (ret)
 				goto free_iommu;
 		}
@@ -3941,6 +3947,7 @@ int __init intel_iommu_init(void)
 	force_on = (!intel_iommu_tboot_noforce && tboot_force_iommu()) ||
 		    platform_optin_force_iommu();
 
+	down_write(&dmar_global_lock);
 	if (dmar_table_init()) {
 		if (force_on)
 			panic("tboot: Failed to initialize DMAR table\n");
@@ -3953,6 +3960,16 @@ int __init intel_iommu_init(void)
 		goto out_free_dmar;
 	}
 
+	up_write(&dmar_global_lock);
+
+	/*
+	 * The bus notifier takes the dmar_global_lock, so lockdep will
+	 * complain later when we register it under the lock.
+	 */
+	dmar_register_bus_notifier();
+
+	down_write(&dmar_global_lock);
+
 	if (!no_iommu)
 		intel_iommu_debugfs_init();
 
@@ -3997,9 +4014,11 @@ int __init intel_iommu_init(void)
 		pr_err("Initialization failed\n");
 		goto out_free_dmar;
 	}
+	up_write(&dmar_global_lock);
 
 	init_iommu_pm_ops();
 
+	down_read(&dmar_global_lock);
 	for_each_active_iommu(iommu, drhd) {
 		/*
 		 * The flush queue implementation does not perform
@@ -4017,10 +4036,12 @@ int __init intel_iommu_init(void)
 				       "%s", iommu->name);
 		iommu_device_register(&iommu->iommu, &intel_iommu_ops, NULL);
 	}
+	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");
 
@@ -4031,15 +4052,17 @@ int __init intel_iommu_init(void)
 
 		iommu_disable_protect_mem_regions(iommu);
 	}
+	up_read(&dmar_global_lock);
 
-	intel_iommu_enabled = 1;
-	dmar_register_bus_notifier();
 	pr_info("Intel(R) Virtualization Technology for Directed I/O\n");
 
+	intel_iommu_enabled = 1;
+
 	return 0;
 
 out_free_dmar:
 	intel_iommu_free_dmars();
+	up_write(&dmar_global_lock);
 	return ret;
 }
 
-- 
2.34.1