[PATCH v5 05/12] iommu/vt-d: Remove SVM_FLAG_SUPERVISOR_MODE support

[Lu Baolu]

The current kernel DMA with PASID support is based on the SVA with a flag
SVM_FLAG_SUPERVISOR_MODE. The IOMMU driver binds the kernel memory address
space to a PASID of the device. The device driver programs the device with
kernel virtual address (KVA) for DMA access. There have been security and
functional issues with this approach:

- The lack of IOTLB synchronization upon kernel page table updates.
  (vmalloc, module/BPF loading, CONFIG_DEBUG_PAGEALLOC etc.)
- Other than slight more protection, using kernel virtual address (KVA)
  has little advantage over physical address. There are also no use
  cases yet where DMA engines need kernel virtual addresses for in-kernel
  DMA.

This removes SVM_FLAG_SUPERVISOR_MODE support in the Intel IOMMU driver.
The device driver is suggested to handle kernel DMA with PASID through
the kernel DMA APIs.

Link: https://lore.kernel.org/linux-iommu/20210511194726.GP1002214@xxxxxxxxxx/
Signed-off-by: Jacob Pan <jacob.jun.pan@xxxxxxxxxxxxxxx>
Signed-off-by: Lu Baolu <baolu.lu@xxxxxxxxxxxxxxx>
---
 drivers/iommu/intel/svm.c | 53 +++++++++------------------------------
 1 file changed, 12 insertions(+), 41 deletions(-)

diff --git a/drivers/iommu/intel/svm.c b/drivers/iommu/intel/svm.c
index 7ee37d996e15..574ddddaa33a 100644
--- a/drivers/iommu/intel/svm.c
+++ b/drivers/iommu/intel/svm.c
@@ -313,8 +313,7 @@ static int pasid_to_svm_sdev(struct device *dev, unsigned int pasid,
 	return 0;
 }
 
-static int intel_svm_alloc_pasid(struct device *dev, struct mm_struct *mm,
-				 unsigned int flags)
+static int intel_svm_alloc_pasid(struct device *dev, struct mm_struct *mm)
 {
 	ioasid_t max_pasid = dev_is_pci(dev) ?
 			pci_max_pasids(to_pci_dev(dev)) : intel_pasid_max_id;
@@ -324,8 +323,7 @@ static int intel_svm_alloc_pasid(struct device *dev, struct mm_struct *mm,
 
 static struct iommu_sva *intel_svm_bind_mm(struct intel_iommu *iommu,
 					   struct device *dev,
-					   struct mm_struct *mm,
-					   unsigned int flags)
+					   struct mm_struct *mm)
 {
 	struct device_domain_info *info = dev_iommu_priv_get(dev);
 	unsigned long iflags, sflags;
@@ -341,22 +339,18 @@ static struct iommu_sva *intel_svm_bind_mm(struct intel_iommu *iommu,
 
 		svm->pasid = mm->pasid;
 		svm->mm = mm;
-		svm->flags = flags;
 		INIT_LIST_HEAD_RCU(&svm->devs);
 
-		if (!(flags & SVM_FLAG_SUPERVISOR_MODE)) {
-			svm->notifier.ops = &intel_mmuops;
-			ret = mmu_notifier_register(&svm->notifier, mm);
-			if (ret) {
-				kfree(svm);
-				return ERR_PTR(ret);
-			}
+		svm->notifier.ops = &intel_mmuops;
+		ret = mmu_notifier_register(&svm->notifier, mm);
+		if (ret) {
+			kfree(svm);
+			return ERR_PTR(ret);
 		}
 
 		ret = pasid_private_add(svm->pasid, svm);
 		if (ret) {
-			if (svm->notifier.ops)
-				mmu_notifier_unregister(&svm->notifier, mm);
+			mmu_notifier_unregister(&svm->notifier, mm);
 			kfree(svm);
 			return ERR_PTR(ret);
 		}
@@ -391,9 +385,7 @@ static struct iommu_sva *intel_svm_bind_mm(struct intel_iommu *iommu,
 	}
 
 	/* Setup the pasid table: */
-	sflags = (flags & SVM_FLAG_SUPERVISOR_MODE) ?
-			PASID_FLAG_SUPERVISOR_MODE : 0;
-	sflags |= cpu_feature_enabled(X86_FEATURE_LA57) ? PASID_FLAG_FL5LP : 0;
+	sflags = cpu_feature_enabled(X86_FEATURE_LA57) ? PASID_FLAG_FL5LP : 0;
 	spin_lock_irqsave(&iommu->lock, iflags);
 	ret = intel_pasid_setup_first_level(iommu, dev, mm->pgd, mm->pasid,
 					    FLPT_DEFAULT_DID, sflags);
@@ -410,8 +402,7 @@ static struct iommu_sva *intel_svm_bind_mm(struct intel_iommu *iommu,
 	kfree(sdev);
 free_svm:
 	if (list_empty(&svm->devs)) {
-		if (svm->notifier.ops)
-			mmu_notifier_unregister(&svm->notifier, mm);
+		mmu_notifier_unregister(&svm->notifier, mm);
 		pasid_private_remove(mm->pasid);
 		kfree(svm);
 	}
@@ -821,37 +812,17 @@ static irqreturn_t prq_event_thread(int irq, void *d)
 struct iommu_sva *intel_svm_bind(struct device *dev, struct mm_struct *mm, void *drvdata)
 {
 	struct intel_iommu *iommu = device_to_iommu(dev, NULL, NULL);
-	unsigned int flags = 0;
 	struct iommu_sva *sva;
 	int ret;
 
-	if (drvdata)
-		flags = *(unsigned int *)drvdata;
-
-	if (flags & SVM_FLAG_SUPERVISOR_MODE) {
-		if (!ecap_srs(iommu->ecap)) {
-			dev_err(dev, "%s: Supervisor PASID not supported\n",
-				iommu->name);
-			return ERR_PTR(-EOPNOTSUPP);
-		}
-
-		if (mm) {
-			dev_err(dev, "%s: Supervisor PASID with user provided mm\n",
-				iommu->name);
-			return ERR_PTR(-EINVAL);
-		}
-
-		mm = &init_mm;
-	}
-
 	mutex_lock(&pasid_mutex);
-	ret = intel_svm_alloc_pasid(dev, mm, flags);
+	ret = intel_svm_alloc_pasid(dev, mm);
 	if (ret) {
 		mutex_unlock(&pasid_mutex);
 		return ERR_PTR(ret);
 	}
 
-	sva = intel_svm_bind_mm(iommu, dev, mm, flags);
+	sva = intel_svm_bind_mm(iommu, dev, mm);
 	mutex_unlock(&pasid_mutex);
 
 	return sva;
-- 
2.25.1