From: Ethan Zhao <haifeng.zhao@linux.intel.com>
To: Kevin Tian <kevin.tian@intel.com>,
Zhenyu Wang <zhenyuw@linux.intel.com>,
Zhi Wang <zhi.a.wang@intel.com>,
Jani Nikula <jani.nikula@linux.intel.com>,
Joonas Lahtinen <joonas.lahtinen@linux.intel.com>,
Rodrigo Vivi <rodrigo.vivi@intel.com>,
Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com>,
David Airlie <airlied@linux.ie>, Daniel Vetter <daniel@ffwll.ch>,
Eric Farman <farman@linux.ibm.com>,
Matthew Rosato <mjrosato@linux.ibm.com>,
Halil Pasic <pasic@linux.ibm.com>,
Vineeth Vijayan <vneethv@linux.ibm.com>,
Peter Oberparleiter <oberpar@linux.ibm.com>,
Heiko Carstens <hca@linux.ibm.com>,
Vasily Gorbik <gor@linux.ibm.com>,
Alexander Gordeev <agordeev@linux.ibm.com>,
Christian Borntraeger <borntraeger@linux.ibm.com>,
Sven Schnelle <svens@linux.ibm.com>,
Tony Krowiak <akrowiak@linux.ibm.com>,
Jason Herne <jjherne@linux.ibm.com>,
Harald Freudenberger <freude@linux.ibm.com>,
Diana Craciun <diana.craciun@oss.nxp.com>,
Alex Williamson <alex.williamson@redhat.com>,
Cornelia Huck <cohuck@redhat.com>,
Longfang Liu <liulongfang@huawei.com>,
Shameer Kolothum <shameerali.kolothum.thodi@huawei.com>,
Jason Gunthorpe <jgg@ziepe.ca>, Yishai Hadas <yishaih@nvidia.com>,
Eric Auger <eric.auger@redhat.com>,
Kirti Wankhede <kwankhede@nvidia.com>,
Leon Romanovsky <leon@kernel.org>,
Abhishek Sahu <abhsahu@nvidia.com>,
Christoph Hellwig <hch@infradead.org>,
intel-gvt-dev@lists.freedesktop.org,
intel-gfx@lists.freedesktop.org, dri-devel@lists.freedesktop.org,
linux-kernel@vger.kernel.org, linux-s390@vger.kernel.org,
kvm@vger.kernel.org
Cc: Yi Liu <yi.l.liu@intel.com>
Subject: Re: [PATCH v3 01/15] vfio: Add helpers for unifying vfio_device life cycle
Date: Fri, 9 Sep 2022 16:23:53 +0800 [thread overview]
Message-ID: <acbaf0f2-91d4-3eae-5716-244893ca34c7@linux.intel.com> (raw)
In-Reply-To: <20220909102247.67324-2-kevin.tian@intel.com>
Hi, Kevin,
在 2022/9/9 18:22, Kevin Tian 写道:
> The idea is to let vfio core manage the vfio_device life cycle instead
> of duplicating the logic cross drivers. This is also a preparatory
> step for adding struct device into vfio_device.
>
> New pair of helpers together with a kref in vfio_device:
>
> - vfio_alloc_device()
> - vfio_put_device()
To be honest, this pair of functions make me confusing to understand their
behaviour from wording point of view:
- vfio_alloc_device(), Okay, it allocates the vfio device, no reference
count thing. but,
- vfio_put_device()
seems it will decrease reference count and then if it is zero, free it.
so they are not of one *pair* about wording.
How about
- vfio_alloc_device() / - vfio_free_device()
or
- vfio_get_device() / - vfio_put_device(), perhaps not match their behviour
in following code.
Thanks,
Ethan
>
> Drivers can register @init/@release callbacks to manage any private
> state wrapping the vfio_device.
>
> However vfio-ccw doesn't fit this model due to a life cycle mess
> that its private structure mixes both parent and mdev info hence must
> be allocated/freed outside of the life cycle of vfio device.
>
> Per prior discussions this won't be fixed in short term by IBM folks.
>
> Instead of waiting for those modifications introduce another helper
> vfio_init_device() so ccw can call it to initialize a pre-allocated
> vfio_device.
>
> Further implication of the ccw trick is that vfio_device cannot be
> freed uniformly in vfio core. Instead, require *EVERY* driver to
> implement @release and free vfio_device inside. Then ccw can choose
> to delay the free at its own discretion.
>
> Another trick down the road is that kvzalloc() is used to accommodate
> the need of gvt which uses vzalloc() while all others use kzalloc().
> So drivers should call a helper vfio_free_device() to free the
> vfio_device instead of assuming that kfree() or vfree() is appliable.
>
> Later once the ccw mess is fixed we can remove those tricks and
> fully handle structure alloc/free in vfio core.
>
> Existing vfio_{un}init_group_dev() will be deprecated after all
> existing usages are converted to the new model.
>
> Suggested-by: Jason Gunthorpe <jgg@nvidia.com>
> Co-developed-by: Yi Liu <yi.l.liu@intel.com>
> Signed-off-by: Yi Liu <yi.l.liu@intel.com>
> Signed-off-by: Kevin Tian <kevin.tian@intel.com>
> Reviewed-by: Tony Krowiak <akrowiak@linux.ibm.com>
> Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
> Reviewed-by: Eric Auger <eric.auger@redhat.com>
> ---
> drivers/vfio/vfio_main.c | 92 ++++++++++++++++++++++++++++++++++++++++
> include/linux/vfio.h | 25 ++++++++++-
> 2 files changed, 116 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/vfio/vfio_main.c b/drivers/vfio/vfio_main.c
> index 27d9186f35d5..adc1b697bb78 100644
> --- a/drivers/vfio/vfio_main.c
> +++ b/drivers/vfio/vfio_main.c
> @@ -498,6 +498,98 @@ void vfio_uninit_group_dev(struct vfio_device *device)
> }
> EXPORT_SYMBOL_GPL(vfio_uninit_group_dev);
>
> +/* Release helper called by vfio_put_device() */
> +void vfio_device_release(struct kref *kref)
> +{
> + struct vfio_device *device =
> + container_of(kref, struct vfio_device, kref);
> +
> + vfio_uninit_group_dev(device);
> +
> + /*
> + * kvfree() cannot be done here due to a life cycle mess in
> + * vfio-ccw. Before the ccw part is fixed all drivers are
> + * required to support @release and call vfio_free_device()
> + * from there.
> + */
> + device->ops->release(device);
> +}
> +EXPORT_SYMBOL_GPL(vfio_device_release);
> +
> +/*
> + * Alloc and initialize vfio_device so it can be registered to vfio
> + * core.
> + *
> + * Drivers should use the wrapper vfio_alloc_device() for allocation.
> + * @size is the size of the structure to be allocated, including any
> + * private data used by the driver.
> + *
> + * Driver may provide an @init callback to cover device private data.
> + *
> + * Use vfio_put_device() to release the structure after success return.
> + */
> +struct vfio_device *_vfio_alloc_device(size_t size, struct device *dev,
> + const struct vfio_device_ops *ops)
> +{
> + struct vfio_device *device;
> + int ret;
> +
> + if (WARN_ON(size < sizeof(struct vfio_device)))
> + return ERR_PTR(-EINVAL);
> +
> + device = kvzalloc(size, GFP_KERNEL);
> + if (!device)
> + return ERR_PTR(-ENOMEM);
> +
> + ret = vfio_init_device(device, dev, ops);
> + if (ret)
> + goto out_free;
> + return device;
> +
> +out_free:
> + kvfree(device);
> + return ERR_PTR(ret);
> +}
> +EXPORT_SYMBOL_GPL(_vfio_alloc_device);
> +
> +/*
> + * Initialize a vfio_device so it can be registered to vfio core.
> + *
> + * Only vfio-ccw driver should call this interface.
> + */
> +int vfio_init_device(struct vfio_device *device, struct device *dev,
> + const struct vfio_device_ops *ops)
> +{
> + int ret;
> +
> + vfio_init_group_dev(device, dev, ops);
> +
> + if (ops->init) {
> + ret = ops->init(device);
> + if (ret)
> + goto out_uninit;
> + }
> +
> + kref_init(&device->kref);
> + return 0;
> +
> +out_uninit:
> + vfio_uninit_group_dev(device);
> + return ret;
> +}
> +EXPORT_SYMBOL_GPL(vfio_init_device);
> +
> +/*
> + * The helper called by driver @release callback to free the device
> + * structure. Drivers which don't have private data to clean can
> + * simply use this helper as its @release.
> + */
> +void vfio_free_device(struct vfio_device *device)
> +{
> + kvfree(device);
> +}
> +EXPORT_SYMBOL_GPL(vfio_free_device);
> +
> static struct vfio_group *vfio_noiommu_group_alloc(struct device *dev,
> enum vfio_group_type type)
> {
> diff --git a/include/linux/vfio.h b/include/linux/vfio.h
> index 0e2826559091..f67cac700e6f 100644
> --- a/include/linux/vfio.h
> +++ b/include/linux/vfio.h
> @@ -47,7 +47,8 @@ struct vfio_device {
> struct kvm *kvm;
>
> /* Members below here are private, not for driver use */
> - refcount_t refcount;
> + struct kref kref; /* object life cycle */
> + refcount_t refcount; /* user count on registered device*/
> unsigned int open_count;
> struct completion comp;
> struct list_head group_next;
> @@ -57,6 +58,8 @@ struct vfio_device {
> /**
> * struct vfio_device_ops - VFIO bus driver device callbacks
> *
> + * @init: initialize private fields in device structure
> + * @release: Reclaim private fields in device structure
> * @open_device: Called when the first file descriptor is opened for this device
> * @close_device: Opposite of open_device
> * @read: Perform read(2) on device file descriptor
> @@ -74,6 +77,8 @@ struct vfio_device {
> */
> struct vfio_device_ops {
> char *name;
> + int (*init)(struct vfio_device *vdev);
> + void (*release)(struct vfio_device *vdev);
> int (*open_device)(struct vfio_device *vdev);
> void (*close_device)(struct vfio_device *vdev);
> ssize_t (*read)(struct vfio_device *vdev, char __user *buf,
> @@ -161,6 +166,24 @@ static inline int vfio_check_feature(u32 flags, size_t argsz, u32 supported_ops,
> return 1;
> }
>
> +struct vfio_device *_vfio_alloc_device(size_t size, struct device *dev,
> + const struct vfio_device_ops *ops);
> +#define vfio_alloc_device(dev_struct, member, dev, ops) \
> + container_of(_vfio_alloc_device(sizeof(struct dev_struct) + \
> + BUILD_BUG_ON_ZERO(offsetof( \
> + struct dev_struct, member)), \
> + dev, ops), \
> + struct dev_struct, member)
> +
> +int vfio_init_device(struct vfio_device *device, struct device *dev,
> + const struct vfio_device_ops *ops);
> +void vfio_free_device(struct vfio_device *device);
> +void vfio_device_release(struct kref *kref);
> +static inline void vfio_put_device(struct vfio_device *device)
> +{
> + kref_put(&device->kref, vfio_device_release);
> +}
> +
> void vfio_init_group_dev(struct vfio_device *device, struct device *dev,
> const struct vfio_device_ops *ops);
> void vfio_uninit_group_dev(struct vfio_device *device);
--
"firm, enduring, strong, and long-lived"
next prev parent reply other threads:[~2022-09-11 6:36 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-09-09 10:22 [PATCH v3 00/15] Tidy up vfio_device life cycle Kevin Tian
2022-09-09 10:22 ` [PATCH v3 01/15] vfio: Add helpers for unifying " Kevin Tian
2022-09-09 8:23 ` Ethan Zhao [this message]
2022-09-09 8:42 ` Tian, Kevin
2022-09-09 23:53 ` Jason Gunthorpe
2022-09-09 10:22 ` [PATCH v3 02/15] vfio/pci: Use the new device life cycle helpers Kevin Tian
2022-09-09 10:22 ` [PATCH v3 03/15] vfio/mlx5: " Kevin Tian
2022-09-09 10:22 ` [PATCH v3 04/15] vfio/hisi_acc: " Kevin Tian
2022-09-09 10:22 ` [PATCH v3 05/15] vfio/mdpy: " Kevin Tian
2022-09-09 10:22 ` [PATCH v3 06/15] vfio/mtty: " Kevin Tian
2022-09-20 19:17 ` Alex Williamson
2022-09-20 22:52 ` Tian, Kevin
2022-09-09 10:22 ` [PATCH v3 07/15] vfio/mbochs: " Kevin Tian
2022-09-09 10:22 ` [PATCH v3 08/15] drm/i915/gvt: " Kevin Tian
2022-09-09 10:22 ` [PATCH v3 09/15] vfio/ap: " Kevin Tian
2022-09-09 10:22 ` [PATCH v3 10/15] vfio/fsl-mc: " Kevin Tian
2022-09-09 10:22 ` [PATCH v3 11/15] vfio/platform: " Kevin Tian
2022-09-09 10:22 ` [PATCH v3 12/15] vfio/amba: " Kevin Tian
2022-09-09 10:22 ` [PATCH v3 13/15] vfio/ccw: " Kevin Tian
2022-09-09 10:22 ` [PATCH v3 14/15] vfio: Rename vfio_device_put() and vfio_device_try_get() Kevin Tian
2022-09-09 10:22 ` [PATCH v3 15/15] vfio: Add struct device to vfio_device Kevin Tian
2022-09-20 20:26 ` Alex Williamson
2022-09-20 22:55 ` Tian, Kevin
2022-09-21 16:10 ` Jason Gunthorpe
2022-09-22 5:18 ` Tian, Kevin
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