iommu/sva: Stop using ioasid_set for SVA

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.

Reviewed-by: Lu Baolu <baolu.lu@linux.intel.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
Signed-off-by: Jacob Pan <jacob.jun.pan@linux.intel.com>
Reviewed-by: Kevin Tian <kevin.tian@intel.com>
Link: https://lore.kernel.org/r/20230322200803.869130-5-jacob.jun.pan@linux.intel.com
Signed-off-by: Joerg Roedel <jroedel@suse.de>

Author: jgunthorpe

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 ||
+	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);
 }

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;