vfio: Simplify capability helper

The vfio_info_add_capability() helper requires the caller to pass a
capability ID, which it then uses to fill in header fields, assuming
hard coded versions.  This makes for an awkward and rigid interface.
The only thing we want this helper to do is allocate sufficient
space in the caps buffer and chain this capability into the list.
Reduce it to that simple task.

Reviewed-by: Alexey Kardashevskiy <aik@ozlabs.ru>
Acked-by: Zhenyu Wang <zhenyuw@linux.intel.com>
Reviewed-by: Kirti Wankhede <kwankhede@nvidia.com>
Reviewed-by: Peter Xu <peterx@redhat.com>
Reviewed-by: Eric Auger <eric.auger@redhat.com>
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>

3 files changed, 22 insertions, 59 deletions

diff --git a/drivers/gpu/drm/i915/gvt/kvmgt.c b/drivers/gpu/drm/i915/gvt/kvmgt.c
index 96060920a6fe..0a7d084da1a2 100644
--- a/drivers/gpu/drm/i915/gvt/kvmgt.c
+++ b/drivers/gpu/drm/i915/gvt/kvmgt.c
@@ -1012,6 +1012,8 @@ static long intel_vgpu_ioctl(struct mdev_device *mdev, unsigned int cmd,
 			if (!sparse)
 				return -ENOMEM;
 
+			sparse->header.id = VFIO_REGION_INFO_CAP_SPARSE_MMAP;
+			sparse->header.version = 1;
 			sparse->nr_areas = nr_areas;
 			cap_type_id = VFIO_REGION_INFO_CAP_SPARSE_MMAP;
 			sparse->areas[0].offset =
@@ -1033,7 +1035,9 @@ static long intel_vgpu_ioctl(struct mdev_device *mdev, unsigned int cmd,
 			break;
 		default:
 			{
-				struct vfio_region_info_cap_type cap_type;
+				struct vfio_region_info_cap_type cap_type = {
+					.header.id = VFIO_REGION_INFO_CAP_TYPE,
+					.header.version = 1 };
 
 				if (info.index >= VFIO_PCI_NUM_REGIONS +
 						vgpu->vdev.num_regions)
@@ -1050,8 +1054,8 @@ static long intel_vgpu_ioctl(struct mdev_device *mdev, unsigned int cmd,
 				cap_type.subtype = vgpu->vdev.region[i].subtype;
 
 				ret = vfio_info_add_capability(&caps,
-						VFIO_REGION_INFO_CAP_TYPE,
-						&cap_type);
+							&cap_type.header,
+							sizeof(cap_type));
 				if (ret)
 					return ret;
 			}
@@ -1061,8 +1065,9 @@ static long intel_vgpu_ioctl(struct mdev_device *mdev, unsigned int cmd,
 			switch (cap_type_id) {
 			case VFIO_REGION_INFO_CAP_SPARSE_MMAP:
 				ret = vfio_info_add_capability(&caps,
-					VFIO_REGION_INFO_CAP_SPARSE_MMAP,
-					sparse);
+					&sparse->header, sizeof(*sparse) +
+					(sparse->nr_areas *
+						sizeof(*sparse->areas)));
 				kfree(sparse);
 				if (ret)
 					return ret;
diff --git a/drivers/vfio/pci/vfio_pci.c b/drivers/vfio/pci/vfio_pci.c
index a98681dca1d3..de48acd29a84 100644
--- a/drivers/vfio/pci/vfio_pci.c
+++ b/drivers/vfio/pci/vfio_pci.c
@@ -585,6 +585,8 @@ static int msix_sparse_mmap_cap(struct vfio_pci_device *vdev,
 	if (!sparse)
 		return -ENOMEM;
 
+	sparse->header.id = VFIO_REGION_INFO_CAP_SPARSE_MMAP;
+	sparse->header.version = 1;
 	sparse->nr_areas = nr_areas;
 
 	if (vdev->msix_offset & PAGE_MASK) {
@@ -600,8 +602,7 @@ static int msix_sparse_mmap_cap(struct vfio_pci_device *vdev,
 		i++;
 	}
 
-	ret = vfio_info_add_capability(caps, VFIO_REGION_INFO_CAP_SPARSE_MMAP,
-				       sparse);
+	ret = vfio_info_add_capability(caps, &sparse->header, size);
 	kfree(sparse);
 
 	return ret;
@@ -744,7 +745,9 @@ static long vfio_pci_ioctl(void *device_data,
 			break;
 		default:
 		{
-			struct vfio_region_info_cap_type cap_type;
+			struct vfio_region_info_cap_type cap_type = {
+					.header.id = VFIO_REGION_INFO_CAP_TYPE,
+					.header.version = 1 };
 
 			if (info.index >=
 			    VFIO_PCI_NUM_REGIONS + vdev->num_regions)
@@ -759,9 +762,8 @@ static long vfio_pci_ioctl(void *device_data,
 			cap_type.type = vdev->region[i].type;
 			cap_type.subtype = vdev->region[i].subtype;
 
-			ret = vfio_info_add_capability(&caps,
-						      VFIO_REGION_INFO_CAP_TYPE,
-						      &cap_type);
+			ret = vfio_info_add_capability(&caps, &cap_type.header,
+						       sizeof(cap_type));
 			if (ret)
 				return ret;
 
diff --git a/drivers/vfio/vfio.c b/drivers/vfio/vfio.c
index 2bc3705a99bd..721f97f8dac1 100644
--- a/drivers/vfio/vfio.c
+++ b/drivers/vfio/vfio.c
@@ -1857,63 +1857,19 @@ void vfio_info_cap_shift(struct vfio_info_cap *caps, size_t offset)
 }
 EXPORT_SYMBOL(vfio_info_cap_shift);
 
-static int sparse_mmap_cap(struct vfio_info_cap *caps, void *cap_type)
+int vfio_info_add_capability(struct vfio_info_cap *caps,
+			     struct vfio_info_cap_header *cap, size_t size)
 {
 	struct vfio_info_cap_header *header;
-	struct vfio_region_info_cap_sparse_mmap *sparse_cap, *sparse = cap_type;
-	size_t size;
 
-	size = sizeof(*sparse) + sparse->nr_areas *  sizeof(*sparse->areas);
-	header = vfio_info_cap_add(caps, size,
-				   VFIO_REGION_INFO_CAP_SPARSE_MMAP, 1);
+	header = vfio_info_cap_add(caps, size, cap->id, cap->version);
 	if (IS_ERR(header))
 		return PTR_ERR(header);
 
-	sparse_cap = container_of(header,
-			struct vfio_region_info_cap_sparse_mmap, header);
-	sparse_cap->nr_areas = sparse->nr_areas;
-	memcpy(sparse_cap->areas, sparse->areas,
-	       sparse->nr_areas * sizeof(*sparse->areas));
-	return 0;
-}
-
-static int region_type_cap(struct vfio_info_cap *caps, void *cap_type)
-{
-	struct vfio_info_cap_header *header;
-	struct vfio_region_info_cap_type *type_cap, *cap = cap_type;
+	memcpy(header + 1, cap + 1, size - sizeof(*header));
 
-	header = vfio_info_cap_add(caps, sizeof(*cap),
-				   VFIO_REGION_INFO_CAP_TYPE, 1);
-	if (IS_ERR(header))
-		return PTR_ERR(header);
-
-	type_cap = container_of(header, struct vfio_region_info_cap_type,
-				header);
-	type_cap->type = cap->type;
-	type_cap->subtype = cap->subtype;
 	return 0;
 }
-
-int vfio_info_add_capability(struct vfio_info_cap *caps, int cap_type_id,
-			     void *cap_type)
-{
-	int ret = -EINVAL;
-
-	if (!cap_type)
-		return 0;
-
-	switch (cap_type_id) {
-	case VFIO_REGION_INFO_CAP_SPARSE_MMAP:
-		ret = sparse_mmap_cap(caps, cap_type);
-		break;
-
-	case VFIO_REGION_INFO_CAP_TYPE:
-		ret = region_type_cap(caps, cap_type);
-		break;
-	}
-
-	return ret;
-}
 EXPORT_SYMBOL(vfio_info_add_capability);
 
 int vfio_set_irqs_validate_and_prepare(struct vfio_irq_set *hdr, int num_irqs,