iommu/sva: Support reservation of global PASIDs

Global PASID allocation is under IOMMU SVA code since it is the primary
use case.  However, some architecture such as VT-d, global PASIDs are
necessary for its internal use of DMA API with PASID.

This patch introduces SVA APIs to reserve and release global PASIDs.

Link: https://lore.kernel.org/all/20230301235646.2692846-4-jacob.jun.pan@linux.intel.com/
Signed-off-by: Jacob Pan <jacob.jun.pan@linux.intel.com>

drivers/iommu/iommu-sva.c

@@ -149,6 +149,31 @@ u32 iommu_sva_get_pasid(struct iommu_sva *handle)
 }
 EXPORT_SYMBOL_GPL(iommu_sva_get_pasid);
 
+ioasid_t iommu_sva_reserve_pasid(ioasid_t min, ioasid_t max)
+{
+	int ret;
+
+	if (min == IOMMU_PASID_INVALID || max == IOMMU_PASID_INVALID ||
+	    min == 0 || 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_sva_reserve_pasid);
+
+void iommu_sva_unreserve_pasid(ioasid_t pasid)
+{
+	if (!pasid_valid(pasid))
+		return;
+
+	ida_free(&iommu_global_pasid_ida, pasid);
+}
+EXPORT_SYMBOL_GPL(iommu_sva_unreserve_pasid);
+
 /*
  * I/O page fault handler for SVA
  */

include/linux/iommu.h

@@ -1192,6 +1192,9 @@ 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_sva_reserve_pasid(ioasid_t min, ioasid_t max);
+void iommu_sva_unreserve_pasid(ioasid_t pasid);
+
 #else
 static inline struct iommu_sva *
 iommu_sva_bind_device(struct device *dev, struct mm_struct *mm)
@@ -1207,6 +1210,17 @@ static inline u32 iommu_sva_get_pasid(struct iommu_sva *handle)
 {
 	return IOMMU_PASID_INVALID;
 }
+
+static inline ioasid_t iommu_sva_reserve_pasid(ioasid_t min, ioasid_t max);
+{
+	return IOMMU_PASID_INVALID;
+}
+
+static inline void iommu_sva_unreserve_pasid(ioasid_t pasid)
+{
+
+}
+
 #endif /* CONFIG_IOMMU_SVA */
 
 #endif /* __LINUX_IOMMU_H */