[PATCH 5/5] iommu/vt-d: Fix lockdep splat in sva bind()/unbind()

From: Lu Baolu <baolu.lu@linux.intel.com>
To: Joerg Roedel <joro@8bytes.org>, Will Deacon <will@kernel.org>
Cc: Ashok Raj <ashok.raj@intel.com>,
	Jacob Pan <jacob.jun.pan@linux.intel.com>,
	Guo Kaijie <Kaijie.Guo@intel.com>, Liu Yi L <yi.l.liu@intel.com>,
	iommu@lists.linux-foundation.org, linux-kernel@vger.kernel.org,
	Lu Baolu <baolu.lu@linux.intel.com>
Subject: [PATCH 5/5] iommu/vt-d: Fix lockdep splat in sva bind()/unbind()
Date: Thu, 31 Dec 2020 08:53:23 +0800	[thread overview]
Message-ID: <20201231005323.2178523-5-baolu.lu@linux.intel.com> (raw)
In-Reply-To: <20201231005323.2178523-1-baolu.lu@linux.intel.com>

Lock(&iommu->lock) without disabling irq causes lockdep warnings.

========================================================
WARNING: possible irq lock inversion dependency detected
5.11.0-rc1+ #828 Not tainted
--------------------------------------------------------
kworker/0:1H/120 just changed the state of lock:
ffffffffad9ea1b8 (device_domain_lock){..-.}-{2:2}, at:
iommu_flush_dev_iotlb.part.0+0x32/0x120
but this lock took another, SOFTIRQ-unsafe lock in the past:
 (&iommu->lock){+.+.}-{2:2}

and interrupts could create inverse lock ordering between them.

other info that might help us debug this:
 Possible interrupt unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock(&iommu->lock);
                               local_irq_disable();
                               lock(device_domain_lock);
                               lock(&iommu->lock);
  <Interrupt>
    lock(device_domain_lock);

 *** DEADLOCK ***

Signed-off-by: Lu Baolu <baolu.lu@linux.intel.com>
---
 drivers/iommu/intel/svm.c | 14 ++++++++------
 1 file changed, 8 insertions(+), 6 deletions(-)

diff --git a/drivers/iommu/intel/svm.c b/drivers/iommu/intel/svm.c
index b16a4791acfb..18a9f05df407 100644
--- a/drivers/iommu/intel/svm.c
+++ b/drivers/iommu/intel/svm.c
@@ -299,6 +299,7 @@ int intel_svm_bind_gpasid(struct iommu_domain *domain, struct device *dev,
 	struct dmar_domain *dmar_domain;
 	struct device_domain_info *info;
 	struct intel_svm *svm = NULL;
+	unsigned long iflags;
 	int ret = 0;
 
 	if (WARN_ON(!iommu) || !data)
@@ -400,12 +401,12 @@ int intel_svm_bind_gpasid(struct iommu_domain *domain, struct device *dev,
 	 * each bind of a new device even with an existing PASID, we need to
 	 * call the nested mode setup function here.
 	 */
-	spin_lock(&iommu->lock);
+	spin_lock_irqsave(&iommu->lock, iflags);
 	ret = intel_pasid_setup_nested(iommu, dev,
 				       (pgd_t *)(uintptr_t)data->gpgd,
 				       data->hpasid, &data->vendor.vtd, dmar_domain,
 				       data->addr_width);
-	spin_unlock(&iommu->lock);
+	spin_unlock_irqrestore(&iommu->lock, iflags);
 	if (ret) {
 		dev_err_ratelimited(dev, "Failed to set up PASID %llu in nested mode, Err %d\n",
 				    data->hpasid, ret);
@@ -505,6 +506,7 @@ intel_svm_bind_mm(struct device *dev, unsigned int flags,
 	struct device_domain_info *info;
 	struct intel_svm_dev *sdev;
 	struct intel_svm *svm = NULL;
+	unsigned long iflags;
 	int pasid_max;
 	int ret;
 
@@ -624,14 +626,14 @@ intel_svm_bind_mm(struct device *dev, unsigned int flags,
 			}
 		}
 
-		spin_lock(&iommu->lock);
+		spin_lock_irqsave(&iommu->lock, iflags);
 		ret = intel_pasid_setup_first_level(iommu, dev,
 				mm ? mm->pgd : init_mm.pgd,
 				svm->pasid, FLPT_DEFAULT_DID,
 				(mm ? 0 : PASID_FLAG_SUPERVISOR_MODE) |
 				(cpu_feature_enabled(X86_FEATURE_LA57) ?
 				 PASID_FLAG_FL5LP : 0));
-		spin_unlock(&iommu->lock);
+		spin_unlock_irqrestore(&iommu->lock, iflags);
 		if (ret) {
 			if (mm)
 				mmu_notifier_unregister(&svm->notifier, mm);
@@ -651,14 +653,14 @@ intel_svm_bind_mm(struct device *dev, unsigned int flags,
 		 * Binding a new device with existing PASID, need to setup
 		 * the PASID entry.
 		 */
-		spin_lock(&iommu->lock);
+		spin_lock_irqsave(&iommu->lock, iflags);
 		ret = intel_pasid_setup_first_level(iommu, dev,
 						mm ? mm->pgd : init_mm.pgd,
 						svm->pasid, FLPT_DEFAULT_DID,
 						(mm ? 0 : PASID_FLAG_SUPERVISOR_MODE) |
 						(cpu_feature_enabled(X86_FEATURE_LA57) ?
 						PASID_FLAG_FL5LP : 0));
-		spin_unlock(&iommu->lock);
+		spin_unlock_irqrestore(&iommu->lock, iflags);
 		if (ret) {
 			kfree(sdev);
 			goto out;
-- 
2.25.1

