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: Wed, 3 Nov 2021 10:25:47 -0300 [thread overview]
Message-ID: <20211103132547.GM2744544@nvidia.com> (raw)
In-Reply-To: <PH0PR11MB565808A9C9974A0D0D72B738C38B9@PH0PR11MB5658.namprd11.prod.outlook.com>
On Tue, Nov 02, 2021 at 09:53:29AM +0000, Liu, Yi L wrote:
> > 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
>
> I see. So the criteria is: the pointer fields pointing to a memory buffer
> allocated by the device driver should be logically be free in a release
> function. right?
Often yes, that is usually a good idea
>I can see there are such fields in struct vfio_pci_core_device
> and mdev_state (both mbochs and mdpy). So we may go with your option #2.
> Is it? otherwise, needs to add release callback for all the related drivers.
Yes, that is the approx trade off
> > On the other hand ccw needs to rcu free the vfio_device, so that would
> > have to be global overhead with this api design.
>
> not quite get. why ccw is special here? could you elaborate?
I added a rcu usage to it in order to fix a race
+static inline struct vfio_ccw_private *vfio_ccw_get_priv(struct subchannel *sch)
+{
+ struct vfio_ccw_private *private;
+
+ rcu_read_lock();
+ private = dev_get_drvdata(&sch->dev);
+ if (private && !vfio_device_try_get(&private->vdev))
+ private = NULL;
+ rcu_read_unlock();
+ return private;
+}
Jason
next prev parent reply other threads:[~2021-11-03 13:25 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
2021-11-02 9:53 ` Liu, Yi L
2021-11-03 13:25 ` Jason Gunthorpe [this message]
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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