[PATCH v2 4/5] iommu: Support mm PASID 1:n with sva domains

[Tina Zhang]

Each mm bound to devices gets a PASID and corresponding sva domains
allocated in iommu_sva_bind_device(), which are referenced by iommu_mm
field of the mm. The PASID is released in __mmdrop(), while a sva domain
is released when no one is using it (the reference count is decremented
in iommu_sva_unbind_device()).

Since the required info of PASID and sva domains is kept in struct
iommu_mm_data of a mm, use mm->iommu_mm field instead of the old pasid
field in mm struct. The sva domain list is protected by iommu_sva_lock.

Besides, this patch removes mm_pasid_init(), as with the introduced
iommu_mm structure, initializing mm pasid in mm_init() is unnecessary.

Signed-off-by: Tina Zhang <tina.zhang@xxxxxxxxx>
---
 drivers/iommu/iommu-sva.c | 38 +++++++++++++++++++++++++-------------
 include/linux/iommu.h     | 10 +++-------
 kernel/fork.c             |  1 -
 3 files changed, 28 insertions(+), 21 deletions(-)

diff --git a/drivers/iommu/iommu-sva.c b/drivers/iommu/iommu-sva.c
index 0a4a1ed40814c..35366f51ad27d 100644
--- a/drivers/iommu/iommu-sva.c
+++ b/drivers/iommu/iommu-sva.c
@@ -15,6 +15,7 @@ static DEFINE_IDA(iommu_global_pasid_ida);
 /* Allocate a PASID for the mm within range (inclusive) */
 static int iommu_sva_alloc_pasid(struct mm_struct *mm, ioasid_t min, ioasid_t max)
 {
+	struct iommu_mm_data *iommu_mm = NULL;
 	int ret = 0;
 
 	if (min == IOMMU_PASID_INVALID ||
@@ -33,11 +34,22 @@ static int iommu_sva_alloc_pasid(struct mm_struct *mm, ioasid_t min, ioasid_t ma
 		goto out;
 	}
 
+	iommu_mm = kzalloc(sizeof(struct iommu_mm_data), GFP_KERNEL);
+	if (!iommu_mm) {
+		ret = -ENOMEM;
+		goto out;
+	}
+
 	ret = ida_alloc_range(&iommu_global_pasid_ida, min, max, GFP_KERNEL);
-	if (ret < 0)
+	if (ret < 0) {
+		kfree(iommu_mm);
 		goto out;
+	}
+
+	iommu_mm->pasid = ret;
+	mm->iommu_mm = iommu_mm;
+	INIT_LIST_HEAD(&mm->iommu_mm->sva_domains);
 
-	mm->pasid = ret;
 	ret = 0;
 out:
 	mutex_unlock(&iommu_sva_lock);
@@ -82,16 +94,12 @@ struct iommu_sva *iommu_sva_bind_device(struct device *dev, struct mm_struct *mm
 
 	mutex_lock(&iommu_sva_lock);
 	/* Search for an existing domain. */
-	domain = iommu_get_domain_for_dev_pasid(dev, mm_get_pasid(mm),
-						IOMMU_DOMAIN_SVA);
-	if (IS_ERR(domain)) {
-		ret = PTR_ERR(domain);
-		goto out_unlock;
-	}
-
-	if (domain) {
-		domain->users++;
-		goto out;
+	list_for_each_entry(domain, &mm->iommu_mm->sva_domains, next) {
+		ret = iommu_attach_device_pasid(domain, dev, mm_get_pasid(mm));
+		if (!ret) {
+			domain->users++;
+			goto out;
+		}
 	}
 
 	/* Allocate a new domain and set it on device pasid. */
@@ -105,6 +113,8 @@ struct iommu_sva *iommu_sva_bind_device(struct device *dev, struct mm_struct *mm
 	if (ret)
 		goto out_free_domain;
 	domain->users = 1;
+	list_add(&domain->next, &mm->iommu_mm->sva_domains);
+
 out:
 	mutex_unlock(&iommu_sva_lock);
 	handle->dev = dev;
@@ -137,8 +147,9 @@ void iommu_sva_unbind_device(struct iommu_sva *handle)
 	struct device *dev = handle->dev;
 
 	mutex_lock(&iommu_sva_lock);
+	iommu_detach_device_pasid(domain, dev, pasid);
 	if (--domain->users == 0) {
-		iommu_detach_device_pasid(domain, dev, pasid);
+		list_del(&domain->next);
 		iommu_domain_free(domain);
 	}
 	mutex_unlock(&iommu_sva_lock);
@@ -218,4 +229,5 @@ void mm_pasid_drop(struct mm_struct *mm)
 		return;
 
 	ida_free(&iommu_global_pasid_ida, mm_get_pasid(mm));
+	kfree(mm->iommu_mm);
 }
diff --git a/include/linux/iommu.h b/include/linux/iommu.h
index 937f3abc26f2e..cfbd35ceb375f 100644
--- a/include/linux/iommu.h
+++ b/include/linux/iommu.h
@@ -109,6 +109,7 @@ struct iommu_domain {
 		struct {	/* IOMMU_DOMAIN_SVA */
 			struct mm_struct *mm;
 			int users;
+			struct list_head next;
 		};
 	};
 };
@@ -1177,17 +1178,13 @@ static inline bool tegra_dev_iommu_get_stream_id(struct device *dev, u32 *stream
 }
 
 #ifdef CONFIG_IOMMU_SVA
-static inline void mm_pasid_init(struct mm_struct *mm)
-{
-	mm->pasid = IOMMU_PASID_INVALID;
-}
 static inline bool mm_valid_pasid(struct mm_struct *mm)
 {
-	return mm->pasid != IOMMU_PASID_INVALID;
+	return mm->iommu_mm ? true : false;
 }
 static inline u32 mm_get_pasid(struct mm_struct *mm)
 {
-	return mm->pasid;
+	return mm->iommu_mm ? mm->iommu_mm->pasid : IOMMU_PASID_INVALID;
 }
 static inline u32 mm_get_enqcmd_pasid(struct mm_struct *mm)
 {
@@ -1213,7 +1210,6 @@ static inline u32 iommu_sva_get_pasid(struct iommu_sva *handle)
 {
 	return IOMMU_PASID_INVALID;
 }
-static inline void mm_pasid_init(struct mm_struct *mm) {}
 static inline bool mm_valid_pasid(struct mm_struct *mm) { return false; }
 static inline u32 mm_get_pasid(struct mm_struct *mm)
 {
diff --git a/kernel/fork.c b/kernel/fork.c
index d2e12b6d2b180..f06392dd1ca8a 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -1274,7 +1274,6 @@ static struct mm_struct *mm_init(struct mm_struct *mm, struct task_struct *p,
 	mm_init_cpumask(mm);
 	mm_init_aio(mm);
 	mm_init_owner(mm, p);
-	mm_pasid_init(mm);
 	RCU_INIT_POINTER(mm->exe_file, NULL);
 	mmu_notifier_subscriptions_init(mm);
 	init_tlb_flush_pending(mm);
-- 
2.34.1