Re: [PATCH v3 03/11] iommufd: Introduce IOMMUFD_OBJ_VIOMMU and its related struct

[Nicolin Chen]

On Sat, Oct 12, 2024 at 11:23:07AM +0800, Zhangfei Gao wrote:
 
> > diff --git a/drivers/iommu/iommufd/viommu_api.c b/drivers/iommu/iommufd/viommu_api.c
> > new file mode 100644
> > index 000000000000..c1731f080d6b
> > --- /dev/null
> > +++ b/drivers/iommu/iommufd/viommu_api.c
> > @@ -0,0 +1,57 @@
> > +// SPDX-License-Identifier: GPL-2.0-only
> > +/* Copyright (c) 2024, NVIDIA CORPORATION & AFFILIATES
> > + */
> > +
> > +#include "iommufd_private.h"
> > +
> > +struct iommufd_object *iommufd_object_alloc_elm(struct iommufd_ctx *ictx,
> > +                                               size_t size,
> > +                                               enum iommufd_object_type type)
> > +{
> > +       struct iommufd_object *obj;
> > +       int rc;
> > +
> > +       obj = kzalloc(size, GFP_KERNEL_ACCOUNT);
> > +       if (!obj)
> > +               return ERR_PTR(-ENOMEM);
> > +       obj->type = type;
> > +       /* Starts out bias'd by 1 until it is removed from the xarray */
> > +       refcount_set(&obj->shortterm_users, 1);
> > +       refcount_set(&obj->users, 1);
> 
> here set refcont 1
> 
> iommufd_device_bind -> iommufd_object_alloc(ictx, idev,
> IOMMUFD_OBJ_DEVICE): refcont -> 1
> refcount_inc(&idev->obj.users); refcount -> 2
> will cause iommufd_device_unbind fail.
> 
> May remove refcount_inc(&idev->obj.users) in iommufd_device_bind

Hmm, why would it fail? Or is it failing on your system?

This patch doesn't change the function but only moved it..

Thanks
Nicolin