linux-kernel - [PATCH v12 4/8] iommu/vt-d: Remove pasid

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Date:   Wed,  2 Aug 2023 14:24:23 -0700
From:   Jacob Pan <jacob.jun.pan@...ux.intel.com>
To:     LKML <linux-kernel@...r.kernel.org>, iommu@...ts.linux.dev,
        "Lu Baolu" <baolu.lu@...ux.intel.com>,
        Joerg Roedel <joro@...tes.org>,
        Jean-Philippe Brucker <jean-philippe@...aro.com>,
        "Robin Murphy" <robin.murphy@....com>
Cc:     Jason Gunthorpe <jgg@...dia.com>, "Will Deacon" <will@...nel.org>,
        "Tian, Kevin" <kevin.tian@...el.com>, Yi Liu <yi.l.liu@...el.com>,
        "Yu, Fenghua" <fenghua.yu@...el.com>,
        Tony Luck <tony.luck@...el.com>,
        Jacob Pan <jacob.jun.pan@...ux.intel.com>
Subject: [PATCH v12 4/8] iommu/vt-d: Remove pasid_mutex

From: Lu Baolu <baolu.lu@...ux.intel.com>

The pasid_mutex was used to protect the paths of set/remove_dev_pasid().
It's duplicate with iommu_sva_lock. Remove it to avoid duplicate code.

Signed-off-by: Lu Baolu <baolu.lu@...ux.intel.com>
Reviewed-by: Jacob Pan <jacob.jun.pan@...ux.intel.com>
Reviewed-by: Kevin Tian <kevin.tian@...el.com>
---
 drivers/iommu/intel/svm.c | 45 +++++----------------------------------
 1 file changed, 5 insertions(+), 40 deletions(-)

diff --git a/drivers/iommu/intel/svm.c b/drivers/iommu/intel/svm.c
index e95b339e9cdc..2a82864e9d57 100644
--- a/drivers/iommu/intel/svm.c
+++ b/drivers/iommu/intel/svm.c
@@ -259,8 +259,6 @@ static const struct mmu_notifier_ops intel_mmuops = {
 	.invalidate_range = intel_invalidate_range,
 };
 
-static DEFINE_MUTEX(pasid_mutex);
-
 static int pasid_to_svm_sdev(struct device *dev, unsigned int pasid,
 			     struct intel_svm **rsvm,
 			     struct intel_svm_dev **rsdev)
@@ -268,10 +266,6 @@ static int pasid_to_svm_sdev(struct device *dev, unsigned int pasid,
 	struct intel_svm_dev *sdev = NULL;
 	struct intel_svm *svm;
 
-	/* The caller should hold the pasid_mutex lock */
-	if (WARN_ON(!mutex_is_locked(&pasid_mutex)))
-		return -EINVAL;
-
 	if (pasid == IOMMU_PASID_INVALID || pasid >= PASID_MAX)
 		return -EINVAL;
 
@@ -371,22 +365,19 @@ static int intel_svm_bind_mm(struct intel_iommu *iommu, struct device *dev,
 	return ret;
 }
 
-/* Caller must hold pasid_mutex */
-static int intel_svm_unbind_mm(struct device *dev, u32 pasid)
+void intel_svm_remove_dev_pasid(struct device *dev, u32 pasid)
 {
 	struct intel_svm_dev *sdev;
 	struct intel_iommu *iommu;
 	struct intel_svm *svm;
 	struct mm_struct *mm;
-	int ret = -EINVAL;
 
 	iommu = device_to_iommu(dev, NULL, NULL);
 	if (!iommu)
-		goto out;
+		return;
 
-	ret = pasid_to_svm_sdev(dev, pasid, &svm, &sdev);
-	if (ret)
-		goto out;
+	if (pasid_to_svm_sdev(dev, pasid, &svm, &sdev))
+		return;
 	mm = svm->mm;
 
 	if (sdev) {
@@ -418,8 +409,6 @@ static int intel_svm_unbind_mm(struct device *dev, u32 pasid)
 			kfree(svm);
 		}
 	}
-out:
-	return ret;
 }
 
 /* Page request queue descriptor */
@@ -520,19 +509,7 @@ static void intel_svm_drain_prq(struct device *dev, u32 pasid)
 		goto prq_retry;
 	}
 
-	/*
-	 * A work in IO page fault workqueue may try to lock pasid_mutex now.
-	 * Holding pasid_mutex while waiting in iopf_queue_flush_dev() for
-	 * all works in the workqueue to finish may cause deadlock.
-	 *
-	 * It's unnecessary to hold pasid_mutex in iopf_queue_flush_dev().
-	 * Unlock it to allow the works to be handled while waiting for
-	 * them to finish.
-	 */
-	lockdep_assert_held(&pasid_mutex);
-	mutex_unlock(&pasid_mutex);
 	iopf_queue_flush_dev(dev);
-	mutex_lock(&pasid_mutex);
 
 	/*
 	 * Perform steps described in VT-d spec CH7.10 to drain page
@@ -827,26 +804,14 @@ int intel_svm_page_response(struct device *dev,
 	return ret;
 }
 
-void intel_svm_remove_dev_pasid(struct device *dev, ioasid_t pasid)
-{
-	mutex_lock(&pasid_mutex);
-	intel_svm_unbind_mm(dev, pasid);
-	mutex_unlock(&pasid_mutex);
-}
-
 static int intel_svm_set_dev_pasid(struct iommu_domain *domain,
 				   struct device *dev, ioasid_t pasid)
 {
 	struct device_domain_info *info = dev_iommu_priv_get(dev);
 	struct intel_iommu *iommu = info->iommu;
 	struct mm_struct *mm = domain->mm;
-	int ret;
 
-	mutex_lock(&pasid_mutex);
-	ret = intel_svm_bind_mm(iommu, dev, mm);
-	mutex_unlock(&pasid_mutex);
-
-	return ret;
+	return intel_svm_bind_mm(iommu, dev, mm);
 }
 
 static void intel_svm_domain_free(struct iommu_domain *domain)
-- 
2.25.1