From 569e4f7782fb92d0e1b395b5fb01de642dd74dcf Mon Sep 17 00:00:00 2001
From: David Woodhouse <David.Woodhouse@intel.com>
Date: Thu, 15 Oct 2015 13:59:14 +0100
Subject: [PATCH] iommu/vt-d: Implement SVM_FLAG_PRIVATE_PASID to allocate
 unique PASIDs

Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>
---
 drivers/iommu/intel-svm.c   |  6 ++++--
 include/linux/intel-iommu.h |  1 +
 include/linux/intel-svm.h   | 11 +++++++++++
 3 files changed, 16 insertions(+), 2 deletions(-)

diff --git a/drivers/iommu/intel-svm.c b/drivers/iommu/intel-svm.c
index 006e95dd64ae..89d4d47d0ab3 100644
--- a/drivers/iommu/intel-svm.c
+++ b/drivers/iommu/intel-svm.c
@@ -285,11 +285,12 @@ int intel_svm_bind_mm(struct device *dev, int *pasid, int flags, struct svm_dev_
 		pasid_max = 1 << 20;
 
 	mutex_lock(&pasid_mutex);
-	if (pasid) {
+	if (pasid && !(flags & SVM_FLAG_PRIVATE_PASID)) {
 		int i;
 
 		idr_for_each_entry(&iommu->pasid_idr, svm, i) {
-			if (svm->mm != current->mm)
+			if (svm->mm != current->mm ||
+			    (svm->flags & SVM_FLAG_PRIVATE_PASID))
 				continue;
 
 			if (svm->pasid >= pasid_max) {
@@ -355,6 +356,7 @@ int intel_svm_bind_mm(struct device *dev, int *pasid, int flags, struct svm_dev_
 		svm->pasid = ret;
 		svm->notifier.ops = &intel_mmuops;
 		svm->mm = get_task_mm(current);
+		svm->flags = flags;
 		INIT_LIST_HEAD_RCU(&svm->devs);
 		ret = -ENOMEM;
 		if (!svm->mm || (ret = mmu_notifier_register(&svm->notifier, svm->mm))) {
diff --git a/include/linux/intel-iommu.h b/include/linux/intel-iommu.h
index 57be14fce640..821273ca4873 100644
--- a/include/linux/intel-iommu.h
+++ b/include/linux/intel-iommu.h
@@ -489,6 +489,7 @@ struct intel_svm {
 	struct mmu_notifier notifier;
 	struct mm_struct *mm;
 	struct intel_iommu *iommu;
+	int flags;
 	int pasid;
 	struct list_head devs;
 };
diff --git a/include/linux/intel-svm.h b/include/linux/intel-svm.h
index 239f8a13a332..dd94ab45a4db 100644
--- a/include/linux/intel-svm.h
+++ b/include/linux/intel-svm.h
@@ -31,6 +31,17 @@ struct svm_dev_ops {
 #define SVM_REQ_EXEC	(1<<1)
 #define SVM_REQ_PRIV	(1<<0)
 
+
+/*
+ * The SVM_FLAG_PRIVATE_PASID flag requests a PASID which is *not* the "main"
+ * PASID for the current process. Even if a PASID already exists, a new one
+ * will be allocated. And the PASID allocated with SVM_FLAG_PRIVATE_PASID
+ * will not be given to subsequent callers. This facility allows a driver to
+ * disambiguate between multiple device contexts which access the same MM,
+ * if there is no other way to do so. It should be used sparingly, if at all.
+ */
+#define SVM_FLAG_PRIVATE_PASID	(1<<0)
+
 /**
  * intel_svm_bind_mm() - Bind the current process to a PASID
  * @dev:	Device to be granted acccess