[PATCH v3 3/7] iommu/sva: Support allocation of global PASIDs outside SVA

[Jacob Pan <jacob.jun.pan@linux.intel.com>]

Devices that use Intel ENQCMD to submit work must use global PASIDs in
that the PASID are stored in a per CPU MSR. When such device need to
submit work for in-kernel DMA with PASID, it must allocate PASIDs from
the same global number space to avoid conflict.

This patch moves global PASID allocation APIs from SVA to IOMMU APIs.
It is expected that device drivers will use the allocated PASIDs to attach
to appropriate IOMMU domains for use.

Signed-off-by: Jacob Pan <jacob.jun.pan@linux.intel.com>
---
 drivers/iommu/iommu-sva.c | 10 ++++------
 drivers/iommu/iommu.c     | 33 +++++++++++++++++++++++++++++++++
 include/linux/iommu.h     | 10 ++++++++++
 3 files changed, 47 insertions(+), 6 deletions(-)

diff --git a/drivers/iommu/iommu-sva.c b/drivers/iommu/iommu-sva.c
index c434b95dc8eb..222544587582 100644
--- a/drivers/iommu/iommu-sva.c
+++ b/drivers/iommu/iommu-sva.c
@@ -9,15 +9,13 @@
 #include "iommu-sva.h"
 
 static DEFINE_MUTEX(iommu_sva_lock);
-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)
 {
 	int ret = 0;
 
-	if (!pasid_valid(min) || !pasid_valid(max) ||
-	    min == 0 || max < min)
+	if (!pasid_valid(min) || !pasid_valid(max) || max < min)
 		return -EINVAL;
 
 	mutex_lock(&iommu_sva_lock);
@@ -28,8 +26,8 @@ static int iommu_sva_alloc_pasid(struct mm_struct *mm, ioasid_t min, ioasid_t ma
 		goto out;
 	}
 
-	ret = ida_alloc_range(&iommu_global_pasid_ida, min, max, GFP_KERNEL);
-	if (ret < min)
+	ret = iommu_alloc_global_pasid(min, max);
+	if (!pasid_valid(ret))
 		goto out;
 	mm->pasid = ret;
 	ret = 0;
@@ -211,5 +209,5 @@ void mm_pasid_drop(struct mm_struct *mm)
 	if (likely(!pasid_valid(mm->pasid)))
 		return;
 
-	ida_free(&iommu_global_pasid_ida, mm->pasid);
+	iommu_free_global_pasid(mm->pasid);
 }
diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
index 10db680acaed..5a8ffdc3063d 100644
--- a/drivers/iommu/iommu.c
+++ b/drivers/iommu/iommu.c
@@ -38,6 +38,7 @@
 
 static struct kset *iommu_group_kset;
 static DEFINE_IDA(iommu_group_ida);
+static DEFINE_IDA(iommu_global_pasid_ida);
 
 static unsigned int iommu_def_domain_type __read_mostly;
 static bool iommu_dma_strict __read_mostly = IS_ENABLED(CONFIG_IOMMU_DEFAULT_DMA_STRICT);
@@ -3450,3 +3451,35 @@ struct iommu_domain *iommu_sva_domain_alloc(struct device *dev,
 
 	return domain;
 }
+
+/**
+ * @brief
+ *	Reserve a PASID from the SVA global number space.
+ *
+ * @param min starting range, inclusive
+ * @param max ending range, inclusive
+ * @return The reserved PASID on success or IOMMU_PASID_INVALID on failure.
+ */
+ioasid_t iommu_alloc_global_pasid(ioasid_t min, ioasid_t max)
+{
+	int ret;
+
+	if (!pasid_valid(min) || !pasid_valid(max) || max < min)
+		return IOMMU_PASID_INVALID;
+
+	ret = ida_alloc_range(&iommu_global_pasid_ida, min, max, GFP_KERNEL);
+	if (ret < 0)
+		return IOMMU_PASID_INVALID;
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(iommu_alloc_global_pasid);
+
+void iommu_free_global_pasid(ioasid_t pasid)
+{
+	if (WARN_ON(!pasid_valid(pasid)))
+		return;
+
+	ida_free(&iommu_global_pasid_ida, pasid);
+}
+EXPORT_SYMBOL_GPL(iommu_free_global_pasid);
diff --git a/include/linux/iommu.h b/include/linux/iommu.h
index 54f535ff9868..f70478a11a5f 100644
--- a/include/linux/iommu.h
+++ b/include/linux/iommu.h
@@ -1187,6 +1187,9 @@ struct iommu_sva *iommu_sva_bind_device(struct device *dev,
 					struct mm_struct *mm);
 void iommu_sva_unbind_device(struct iommu_sva *handle);
 u32 iommu_sva_get_pasid(struct iommu_sva *handle);
+ioasid_t iommu_alloc_global_pasid(ioasid_t min, ioasid_t max);
+void iommu_free_global_pasid(ioasid_t pasid);
+
 #else
 static inline struct iommu_sva *
 iommu_sva_bind_device(struct device *dev, struct mm_struct *mm)
@@ -1202,6 +1205,13 @@ static inline u32 iommu_sva_get_pasid(struct iommu_sva *handle)
 {
 	return IOMMU_PASID_INVALID;
 }
+
+static inline ioasid_t iommu_alloc_global_pasid(ioasid_t min, ioasid_t max)
+{
+	return IOMMU_PASID_INVALID;
+}
+
+static inline void iommu_free_global_pasid(ioasid_t pasid) {}
 static inline void mm_pasid_init(struct mm_struct *mm) {}
 static inline void mm_pasid_drop(struct mm_struct *mm) {}
 #endif /* CONFIG_IOMMU_SVA */
-- 
2.25.1