iommu/virtio: Pass end address to viommu_add_mapping()

To support identity mappings, the virtio-iommu driver must be able to
represent full 64-bit ranges internally. Pass (start, end) instead of
(start, size) to viommu_add/del_mapping().

Clean comments. The one about the returned size was never true: when
sweeping the whole address space the returned size will most certainly
be smaller than 2^64.

Reviewed-by: Eric Auger <eric.auger@redhat.com>
Reviewed-by: Kevin Tian <kevin.tian@intel.com>
Signed-off-by: Jean-Philippe Brucker <jean-philippe@linaro.org>
Link: https://lore.kernel.org/r/20211201173323.1045819-5-jean-philippe@linaro.org
Signed-off-by: Joerg Roedel <jroedel@suse.de>

Author: Jean-Philippe Brucker

drivers/iommu/virtio-iommu.c

@@ -311,8 +311,8 @@ static int viommu_send_req_sync(struct viommu_dev *viommu, void *buf,
  *
  * On success, return the new mapping. Otherwise return NULL.
  */
-static int viommu_add_mapping(struct viommu_domain *vdomain, unsigned long iova,
-			      phys_addr_t paddr, size_t size, u32 flags)
+static int viommu_add_mapping(struct viommu_domain *vdomain, u64 iova, u64 end,
+			      phys_addr_t paddr, u32 flags)
 {
 	unsigned long irqflags;
 	struct viommu_mapping *mapping;
@@ -323,7 +323,7 @@ static int viommu_add_mapping(struct viommu_domain *vdomain, unsigned long iova,
 
 	mapping->paddr		= paddr;
 	mapping->iova.start	= iova;
-	mapping->iova.last	= iova + size - 1;
+	mapping->iova.last	= end;
 	mapping->flags		= flags;
 
 	spin_lock_irqsave(&vdomain->mappings_lock, irqflags);
@@ -338,26 +338,24 @@ static int viommu_add_mapping(struct viommu_domain *vdomain, unsigned long iova,
  *
  * @vdomain: the domain
  * @iova: start of the range
- * @size: size of the range. A size of 0 corresponds to the entire address
- *	space.
+ * @end: end of the range
  *
- * On success, returns the number of unmapped bytes (>= size)
+ * On success, returns the number of unmapped bytes
  */
 static size_t viommu_del_mappings(struct viommu_domain *vdomain,
-				  unsigned long iova, size_t size)
+				  u64 iova, u64 end)
 {
 	size_t unmapped = 0;
 	unsigned long flags;
-	unsigned long last = iova + size - 1;
 	struct viommu_mapping *mapping = NULL;
 	struct interval_tree_node *node, *next;
 
 	spin_lock_irqsave(&vdomain->mappings_lock, flags);
-	next = interval_tree_iter_first(&vdomain->mappings, iova, last);
+	next = interval_tree_iter_first(&vdomain->mappings, iova, end);
 	while (next) {
 		node = next;
 		mapping = container_of(node, struct viommu_mapping, iova);
-		next = interval_tree_iter_next(node, iova, last);
+		next = interval_tree_iter_next(node, iova, end);
 
 		/* Trying to split a mapping? */
 		if (mapping->iova.start < iova)
@@ -656,8 +654,8 @@ static void viommu_domain_free(struct iommu_domain *domain)
 {
 	struct viommu_domain *vdomain = to_viommu_domain(domain);
 
-	/* Free all remaining mappings (size 2^64) */
-	viommu_del_mappings(vdomain, 0, 0);
+	/* Free all remaining mappings */
+	viommu_del_mappings(vdomain, 0, ULLONG_MAX);
 
 	if (vdomain->viommu)
 		ida_free(&vdomain->viommu->domain_ids, vdomain->id);
@@ -742,6 +740,7 @@ static int viommu_map(struct iommu_domain *domain, unsigned long iova,
 {
 	int ret;
 	u32 flags;
+	u64 end = iova + size - 1;
 	struct virtio_iommu_req_map map;
 	struct viommu_domain *vdomain = to_viommu_domain(domain);
 
@@ -752,7 +751,7 @@ static int viommu_map(struct iommu_domain *domain, unsigned long iova,
 	if (flags & ~vdomain->map_flags)
 		return -EINVAL;
 
-	ret = viommu_add_mapping(vdomain, iova, paddr, size, flags);
+	ret = viommu_add_mapping(vdomain, iova, end, paddr, flags);
 	if (ret)
 		return ret;
 
@@ -761,7 +760,7 @@ static int viommu_map(struct iommu_domain *domain, unsigned long iova,
 		.domain		= cpu_to_le32(vdomain->id),
 		.virt_start	= cpu_to_le64(iova),
 		.phys_start	= cpu_to_le64(paddr),
-		.virt_end	= cpu_to_le64(iova + size - 1),
+		.virt_end	= cpu_to_le64(end),
 		.flags		= cpu_to_le32(flags),
 	};
 
@@ -770,7 +769,7 @@ static int viommu_map(struct iommu_domain *domain, unsigned long iova,
 
 	ret = viommu_send_req_sync(vdomain->viommu, &map, sizeof(map));
 	if (ret)
-		viommu_del_mappings(vdomain, iova, size);
+		viommu_del_mappings(vdomain, iova, end);
 
 	return ret;
 }
@@ -783,7 +782,7 @@ static size_t viommu_unmap(struct iommu_domain *domain, unsigned long iova,
 	struct virtio_iommu_req_unmap unmap;
 	struct viommu_domain *vdomain = to_viommu_domain(domain);
 
-	unmapped = viommu_del_mappings(vdomain, iova, size);
+	unmapped = viommu_del_mappings(vdomain, iova, iova + size - 1);
 	if (unmapped < size)
 		return 0;