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

[Yi Liu]

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....@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