From: Jason Gunthorpe <jgg@nvidia.com>
To: "Liu, Yi L" <yi.l.liu@intel.com>
Cc: "alex.williamson@redhat.com" <alex.williamson@redhat.com>,
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Subject: Re: [RFC 02/20] vfio: Add device class for /dev/vfio/devices
Date: Mon, 1 Nov 2021 09:50:13 -0300 [thread overview]
Message-ID: <20211101125013.GL2744544@nvidia.com> (raw)
In-Reply-To: <PH0PR11MB56586D2EC89F282C915AF18DC3879@PH0PR11MB5658.namprd11.prod.outlook.com>
On Fri, Oct 29, 2021 at 09:47:27AM +0000, Liu, Yi L wrote:
> Hi Jason,
>
> > From: Jason Gunthorpe <jgg@nvidia.com>
> > Sent: Monday, October 25, 2021 8:53 PM
> >
> > On Mon, Oct 25, 2021 at 06:28:09AM +0000, Liu, Yi L wrote:
> > > thanks for the guiding. will also refer to your vfio_group_cdev series.
> > >
> > > Need to double confirm here. Not quite following on the kfree. Is
> > > this kfree to free the vfio_device structure? But now the
> > > vfio_device pointer is provided by callers (e.g. vfio-pci). Do
> > > you want to let vfio core allocate the vfio_device struct and
> > > return the pointer to callers?
> >
> > There are several common patterns for this problem, two that would be
> > suitable:
> >
> > - Require each driver to provide a release op inside vfio_device_ops
> > that does the kfree. Have the core provide a struct device release
> > op that calls this one. Keep the kalloc/kfree in the drivers
>
> this way sees to suit the existing vfio registration manner listed
> below. right?
Not really, most drivers are just doing kfree. The need for release
comes if the drivers are doing more stuff.
> But device drivers needs to do the kfree in the
> newly added release op instead of doing it on their own (e.g.
> doing kfree in remove).
Yes
> > struct ib_device *_ib_alloc_device(size_t size);
> > #define ib_alloc_device(drv_struct, member) \
> > container_of(_ib_alloc_device(sizeof(struct drv_struct) + \
> > BUILD_BUG_ON_ZERO(offsetof( \
> > struct drv_struct, member))), \
> > struct drv_struct, member)
> >
>
> thanks for the example. If this way, still requires driver to provide
> a release op inside vfio_device_ops. right?
No, it would optional. It would contain the stuff the driver is doing
before kfree()
For instance mdev looks like the only driver that cares:
vfio_uninit_group_dev(&mdev_state->vdev);
kfree(mdev_state->pages);
kfree(mdev_state->vconfig);
kfree(mdev_state);
pages/vconfig would logically be in a release function
On the other hand ccw needs to rcu free the vfio_device, so that would
have to be global overhead with this api design.
Jason
next prev parent reply other threads:[~2021-11-01 12:50 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <PH0PR11MB56583D477B3977D92C2C1ADDC3839@PH0PR11MB5658.namprd11.prod.outlook.com>
2021-10-25 12:53 ` [RFC 02/20] vfio: Add device class for /dev/vfio/devices Jason Gunthorpe
2021-10-29 9:47 ` Liu, Yi L
2021-11-01 12:50 ` Jason Gunthorpe [this message]
2021-11-02 9:53 ` Liu, Yi L
2021-11-03 13:25 ` Jason Gunthorpe
2021-11-11 12:32 ` Liu, Yi L
2021-09-19 6:38 [RFC 00/20] Introduce /dev/iommu for userspace I/O address space management Liu Yi L
2021-09-19 6:38 ` [RFC 02/20] vfio: Add device class for /dev/vfio/devices Liu Yi L
2021-09-21 15:57 ` Jason Gunthorpe
2021-09-21 23:56 ` Tian, Kevin
2021-09-22 0:55 ` Jason Gunthorpe
2021-09-22 1:07 ` Tian, Kevin
2021-09-22 12:31 ` Jason Gunthorpe
2021-09-22 3:22 ` Tian, Kevin
2021-09-22 12:50 ` Jason Gunthorpe
2021-09-22 14:09 ` Tian, Kevin
2021-09-21 19:56 ` Alex Williamson
2021-09-22 0:56 ` Tian, Kevin
2021-09-29 2:08 ` David Gibson
2021-09-29 19:05 ` Alex Williamson
2021-09-30 2:43 ` David Gibson
2021-10-20 12:39 ` Liu, Yi L
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