linux-kernel - Re: [PATCH v3 03/11] iommufd: Introduce IOMMUFD_OBJ

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Message-ID: <Zwn/4m8Ac0xEiJi8@Asurada-Nvidia>
Date: Fri, 11 Oct 2024 21:49:38 -0700
From: Nicolin Chen <nicolinc@...dia.com>
To: Zhangfei Gao <zhangfei.gao@...aro.org>
CC: <jgg@...dia.com>, <kevin.tian@...el.com>, <will@...nel.org>,
	<joro@...tes.org>, <suravee.suthikulpanit@....com>, <robin.murphy@....com>,
	<dwmw2@...radead.org>, <baolu.lu@...ux.intel.com>, <shuah@...nel.org>,
	<linux-kernel@...r.kernel.org>, <iommu@...ts.linux.dev>,
	<linux-arm-kernel@...ts.infradead.org>, <linux-kselftest@...r.kernel.org>,
	<eric.auger@...hat.com>, <jean-philippe@...aro.org>, <mdf@...nel.org>,
	<mshavit@...gle.com>, <shameerali.kolothum.thodi@...wei.com>,
	<smostafa@...gle.com>, <yi.l.liu@...el.com>, <aik@....com>,
	<patches@...ts.linux.dev>
Subject: Re: [PATCH v3 03/11] iommufd: Introduce IOMMUFD_OBJ_VIOMMU and its
 related struct

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