[PATCH v6 4/7] iommu/sva: Stop using ioasid_set for SVA

[Jacob Pan <jacob.jun.pan@xxxxxxxxxxxxxxx>]

From: Jason Gunthorpe <jgg@xxxxxxxxxx>

Instead SVA drivers can use a simple global IDA to allocate PASIDs for
each mm_struct.

Future work would be to allow drivers using the SVA APIs to reserve global
PASIDs from this IDA for their internal use, eg with the DMA API PASID
support.

Signed-off-by: Jason Gunthorpe <jgg@xxxxxxxxxx>
Signed-off-by: Jacob Pan <jacob.jun.pan@xxxxxxxxxxxxxxx>
---
v5:
	- Put removing iommu_sva_find() to a separate patch (Kevin)
	- Make pasid allocation range to be inclusive (Tina)
	- Simplified return code handling (Baolu)
v4:
	- Keep GFP_ATOMIC flag for PASID allocation, will changed to
	GFP_KERNEL in a separate patch.
---
 drivers/iommu/iommu-sva.c | 43 ++++++++++++++-------------------------
 drivers/iommu/iommu-sva.h |  2 --
 2 files changed, 15 insertions(+), 30 deletions(-)

diff --git a/drivers/iommu/iommu-sva.c b/drivers/iommu/iommu-sva.c
index 4f357ef14f04..d4640731727a 100644
--- a/drivers/iommu/iommu-sva.c
+++ b/drivers/iommu/iommu-sva.c
@@ -9,47 +9,34 @@
 #include "iommu-sva.h"
 
 static DEFINE_MUTEX(iommu_sva_lock);
-static DECLARE_IOASID_SET(iommu_sva_pasid);
+static DEFINE_IDA(iommu_global_pasid_ida);
 
-/**
- * iommu_sva_alloc_pasid - Allocate a PASID for the mm
- * @mm: the mm
- * @min: minimum PASID value (inclusive)
- * @max: maximum PASID value (inclusive)
- *
- * Try to allocate a PASID for this mm, or take a reference to the existing one
- * provided it fits within the [@min, @max] range. On success the PASID is
- * available in mm->pasid and will be available for the lifetime of the mm.
- *
- * Returns 0 on success and < 0 on error.
- */
-int iommu_sva_alloc_pasid(struct mm_struct *mm, ioasid_t min, ioasid_t max)
+/* 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;
-	ioasid_t pasid;
 
-	if (min == INVALID_IOASID || max == INVALID_IOASID ||
-	    min == 0 || max < min)
+	if (!pasid_valid(min) || !pasid_valid(max) ||
+	     min == 0 || max < min)
 		return -EINVAL;
 
 	mutex_lock(&iommu_sva_lock);
 	/* Is a PASID already associated with this mm? */
 	if (pasid_valid(mm->pasid)) {
-		if (mm->pasid < min || mm->pasid >= max)
+		if (mm->pasid < min || mm->pasid > max)
 			ret = -EOVERFLOW;
 		goto out;
 	}
 
-	pasid = ioasid_alloc(&iommu_sva_pasid, min, max, mm);
-	if (!pasid_valid(pasid))
-		ret = -ENOMEM;
-	else
-		mm->pasid = pasid;
+	ret = ida_alloc_range(&iommu_global_pasid_ida, min, max, GFP_ATOMIC);
+	if (ret < 0)
+		goto out;
+	mm->pasid = ret;
+	ret = 0;
 out:
 	mutex_unlock(&iommu_sva_lock);
 	return ret;
 }
-EXPORT_SYMBOL_GPL(iommu_sva_alloc_pasid);
 
 /**
  * iommu_sva_bind_device() - Bind a process address space to a device
@@ -221,8 +208,8 @@ iommu_sva_handle_iopf(struct iommu_fault *fault, void *data)
 
 void mm_pasid_drop(struct mm_struct *mm)
 {
-	if (pasid_valid(mm->pasid)) {
-		ioasid_free(mm->pasid);
-		mm->pasid = INVALID_IOASID;
-	}
+	if (likely(!pasid_valid(mm->pasid)))
+		return;
+
+	ida_free(&iommu_global_pasid_ida, mm->pasid);
 }
diff --git a/drivers/iommu/iommu-sva.h b/drivers/iommu/iommu-sva.h
index 102eae1817a2..c22d0174ad61 100644
--- a/drivers/iommu/iommu-sva.h
+++ b/drivers/iommu/iommu-sva.h
@@ -8,8 +8,6 @@
 #include <linux/ioasid.h>
 #include <linux/mm_types.h>
 
-int iommu_sva_alloc_pasid(struct mm_struct *mm, ioasid_t min, ioasid_t max);
-
 /* I/O Page fault */
 struct device;
 struct iommu_fault;
-- 
2.25.1