From: Jason Wang <jasowang@redhat.com>
To: Jason Gunthorpe <jgg@mellanox.com>
Cc: "mst@redhat.com" <mst@redhat.com>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
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Parav Pandit <parav@mellanox.com>,
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Jiri Pirko <jiri@mellanox.com>,
Shahaf Shuler <shahafs@mellanox.com>,
"hanand@xilinx.com" <hanand@xilinx.com>,
"mhabets@solarflare.com" <mhabets@solarflare.com>
Subject: Re: [PATCH 4/5] virtio: introduce a vDPA based transport
Date: Mon, 20 Jan 2020 15:52:12 +0800 [thread overview]
Message-ID: <bff37791-9640-39e0-5e93-c905ebfb5d2b@redhat.com> (raw)
In-Reply-To: <20200117140013.GV20978@mellanox.com>
On 2020/1/17 下午10:00, Jason Gunthorpe wrote:
> On Fri, Jan 17, 2020 at 05:32:35PM +0800, Jason Wang wrote:
>>>> + const struct vdpa_config_ops *ops = vdpa->config;
>>>> + struct virtio_vdpa_device *vd_dev;
>>>> + int rc;
>>>> +
>>>> + vd_dev = devm_kzalloc(dev, sizeof(*vd_dev), GFP_KERNEL);
>>>> + if (!vd_dev)
>>>> + return -ENOMEM;
>>> This is not right, the struct device lifetime is controled by a kref,
>>> not via devm. If you want to use a devm unwind then the unwind is
>>> put_device, not devm_kfree.
>> I'm not sure I get the point here. The lifetime is bound to underlying vDPA
>> device and devres allow to be freed before the vpda device is released. But
>> I agree using devres of underlying vdpa device looks wired.
> Once device_initialize is called the only way to free a struct device
> is via put_device, while here you have a devm trigger that will
> unconditionally do kfree on a struct device without respecting the
> reference count.
>
> reference counted memory must never be allocated with devm.
Right, fixed.
>
>>>> + vd_dev->vdev.dev.release = virtio_vdpa_release_dev;
>>>> + vd_dev->vdev.config = &virtio_vdpa_config_ops;
>>>> + vd_dev->vdpa = vdpa;
>>>> + INIT_LIST_HEAD(&vd_dev->virtqueues);
>>>> + spin_lock_init(&vd_dev->lock);
>>>> +
>>>> + vd_dev->vdev.id.device = ops->get_device_id(vdpa);
>>>> + if (vd_dev->vdev.id.device == 0)
>>>> + return -ENODEV;
>>>> +
>>>> + vd_dev->vdev.id.vendor = ops->get_vendor_id(vdpa);
>>>> + rc = register_virtio_device(&vd_dev->vdev);
>>>> + if (rc)
>>>> + put_device(dev);
>>> And a ugly unwind like this is why you want to have device_initialize()
>>> exposed to the driver,
>> In this context, which "driver" did you mean here? (Note, virtio-vdpa is the
>> driver for vDPA bus here).
> 'driver' is the thing using the 'core' library calls to implement a
> device, so here the 'vd_dev' is the driver and
> 'register_virtio_device' is the core
Ok.
>
>>> Where is the various THIS_MODULE's I expect to see in a scheme like
>>> this?
>>>
>>> All function pointers must be protected by a held module reference
>>> count, ie the above probe/remove and all the pointers in ops.
>> Will double check, since I don't see this in other virtio transport drivers
>> (PCI or MMIO).
> pci_register_driver is a macro that provides a THIS_MODULE, and the
> pci core code sets driver.owner, then the rest of the stuff related to
> driver ops is supposed to work against that to protect the driver ops.
>
> For the device module refcounting you either need to ensure that
> 'unregister' is a strong fence and guanentees that no device ops are
> called past unregister (noting that this is impossible for release),
> or you need to hold the module lock until release.
>
> It is common to see non-core subsystems get this stuff wrong.
>
> Jason
Ok. I see.
Thanks
next prev parent reply other threads:[~2020-01-20 7:52 UTC|newest]
Thread overview: 76+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-01-16 12:42 [PATCH 0/5] vDPA support Jason Wang
2020-01-16 12:42 ` [PATCH 1/5] vhost: factor out IOTLB Jason Wang
2020-01-17 4:14 ` Randy Dunlap
2020-01-17 9:34 ` Jason Wang
2020-01-18 0:01 ` kbuild test robot
2020-01-18 0:40 ` kbuild test robot
2020-01-16 12:42 ` [PATCH 2/5] vringh: IOTLB support Jason Wang
2020-01-17 21:54 ` kbuild test robot
2020-01-17 22:33 ` kbuild test robot
2020-01-16 12:42 ` [PATCH 3/5] vDPA: introduce vDPA bus Jason Wang
2020-01-16 15:22 ` Jason Gunthorpe
2020-01-17 3:03 ` Jason Wang
2020-01-17 13:54 ` Jason Gunthorpe
2020-01-20 7:50 ` Jason Wang
2020-01-20 12:17 ` Michael S. Tsirkin
2020-01-20 17:50 ` Jason Gunthorpe
2020-01-20 21:56 ` Michael S. Tsirkin
2020-01-21 14:12 ` Jason Gunthorpe
2020-01-21 14:15 ` Michael S. Tsirkin
2020-01-21 14:16 ` Jason Gunthorpe
2020-01-21 8:40 ` Tian, Kevin
2020-01-21 9:41 ` Jason Wang
2020-01-17 4:16 ` Randy Dunlap
2020-01-17 9:34 ` Jason Wang
2020-01-17 12:13 ` Michael S. Tsirkin
2020-01-17 13:52 ` Jason Wang
[not found] ` <CAJPjb1+fG9L3=iKbV4Vn13VwaeDZZdcfBPvarogF_Nzhk+FnKg@mail.gmail.com>
2020-01-19 9:07 ` Shahaf Shuler
2020-01-19 9:59 ` Michael S. Tsirkin
2020-01-20 8:44 ` Jason Wang
2020-01-20 12:09 ` Michael S. Tsirkin
2020-01-21 3:32 ` Jason Wang
2020-01-20 8:43 ` Jason Wang
2020-01-20 17:49 ` Jason Gunthorpe
2020-01-20 20:51 ` Shahaf Shuler
2020-01-20 21:25 ` Michael S. Tsirkin
2020-01-20 21:47 ` Shahaf Shuler
2020-01-20 21:59 ` Michael S. Tsirkin
2020-01-21 6:01 ` Shahaf Shuler
2020-01-21 7:57 ` Jason Wang
2020-01-21 14:07 ` Jason Gunthorpe
2020-01-21 14:16 ` Michael S. Tsirkin
2020-01-20 21:48 ` Michael S. Tsirkin
2020-01-21 4:00 ` Jason Wang
2020-01-21 5:47 ` Michael S. Tsirkin
2020-01-21 8:00 ` Jason Wang
2020-01-21 8:15 ` Michael S. Tsirkin
2020-01-21 8:35 ` Jason Wang
2020-01-21 11:09 ` Shahaf Shuler
2020-01-22 6:36 ` Jason Wang
2020-01-21 14:05 ` Jason Gunthorpe
2020-01-21 14:17 ` Michael S. Tsirkin
2020-01-22 6:18 ` Jason Wang
2020-01-20 8:19 ` Jason Wang
2020-01-16 12:42 ` [PATCH 4/5] virtio: introduce a vDPA based transport Jason Wang
2020-01-16 15:38 ` Jason Gunthorpe
2020-01-17 9:32 ` Jason Wang
2020-01-17 14:00 ` Jason Gunthorpe
2020-01-20 7:52 ` Jason Wang [this message]
2020-01-17 4:10 ` Randy Dunlap
2020-01-16 12:42 ` [PATCH 5/5] vdpasim: vDPA device simulator Jason Wang
2020-01-16 15:47 ` Jason Gunthorpe
2020-01-17 9:32 ` Jason Wang
2020-01-17 14:10 ` Jason Gunthorpe
2020-01-20 8:01 ` Jason Wang
2020-02-04 4:19 ` Jason Wang
2020-01-17 4:12 ` Randy Dunlap
2020-01-17 9:35 ` Jason Wang
2020-01-18 18:18 ` kbuild test robot
2020-01-28 3:32 ` Dan Carpenter
2020-02-04 4:07 ` Jason Wang
2020-02-04 8:21 ` Zhu Lingshan
2020-02-04 8:28 ` Jason Wang
2020-02-04 12:52 ` Jason Gunthorpe
2020-02-05 3:14 ` Jason Wang
2020-01-21 8:44 ` [PATCH 0/5] vDPA support Tian, Kevin
2020-01-21 9:39 ` Jason Wang
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