[PATCH v4 6/9] iommufd: Reserved -1 in the iommufd xarray

Yi Liu
2023-04-26T14:54:41Z

VFIO needs two reserved values. 0 is already reserved by initializing
xarray with XA_FLAGS_ALLOC1. This reserves -1 by limiting the xa alloc
range.

Signed-off-by: Yi Liu <yi.l.liu@intel.com>
---
drivers/iommu/iommufd/main.c | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/drivers/iommu/iommufd/main.c b/drivers/iommu/iommufd/main.c
index 3fbe636c3d8a..51b27c96c52f 100644
--- a/drivers/iommu/iommufd/main.c
+++ b/drivers/iommu/iommufd/main.c
@@ -28,6 +28,9 @@ struct iommufd_object_ops {
static const struct iommufd_object_ops iommufd_object_ops[];
static struct miscdevice vfio_misc_dev;

+/* -1 is reserved */
+#define iommufd_xa_limit_32b XA_LIMIT(0, (-2U))
+
struct iommufd_object *_iommufd_object_alloc(struct iommufd_ctx *ictx,
size_t size,
enum iommufd_object_type type)
@@ -50,7 +53,7 @@ struct iommufd_object *_iommufd_object_alloc(struct iommufd_ctx *ictx,
* before calling iommufd_object_finalize().
*/
rc = xa_alloc(&ictx->objects, &obj->id, XA_ZERO_ENTRY,
- xa_limit_32b, GFP_KERNEL_ACCOUNT);
+ iommufd_xa_limit_32b, GFP_KERNEL_ACCOUNT);
if (rc)
goto out_free;
return obj;
--
2.34.1