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Message-ID: <1faf4f36-3f79-2e15-3f61-c406d68240ab@redhat.com>
Date: Tue, 5 Nov 2019 11:52:41 +0800
From: Jason Wang <jasowang@...hat.com>
To: Alex Williamson <alex.williamson@...hat.com>
Cc: kvm@...r.kernel.org, linux-s390@...r.kernel.org,
linux-kernel@...r.kernel.org, dri-devel@...ts.freedesktop.org,
intel-gfx@...ts.freedesktop.org,
intel-gvt-dev@...ts.freedesktop.org, kwankhede@...dia.com,
mst@...hat.com, tiwei.bie@...el.com,
virtualization@...ts.linux-foundation.org, netdev@...r.kernel.org,
cohuck@...hat.com, maxime.coquelin@...hat.com,
cunming.liang@...el.com, zhihong.wang@...el.com,
rob.miller@...adcom.com, xiao.w.wang@...el.com,
haotian.wang@...ive.com, zhenyuw@...ux.intel.com,
zhi.a.wang@...el.com, jani.nikula@...ux.intel.com,
joonas.lahtinen@...ux.intel.com, rodrigo.vivi@...el.com,
airlied@...ux.ie, daniel@...ll.ch, farman@...ux.ibm.com,
pasic@...ux.ibm.com, sebott@...ux.ibm.com, oberpar@...ux.ibm.com,
heiko.carstens@...ibm.com, gor@...ux.ibm.com,
borntraeger@...ibm.com, akrowiak@...ux.ibm.com,
freude@...ux.ibm.com, lingshan.zhu@...el.com, idos@...lanox.com,
eperezma@...hat.com, lulu@...hat.com, parav@...lanox.com,
christophe.de.dinechin@...il.com, kevin.tian@...el.com,
stefanha@...hat.com
Subject: Re: [PATCH V7 4/6] mdev: introduce virtio device and its device ops
On 2019/11/5 上午5:50, Alex Williamson wrote:
> On Mon, 4 Nov 2019 20:39:50 +0800
> Jason Wang <jasowang@...hat.com> wrote:
>
>> This patch implements basic support for mdev driver that supports
>> virtio transport for kernel virtio driver.
>>
>> Signed-off-by: Jason Wang <jasowang@...hat.com>
>> ---
>> drivers/vfio/mdev/mdev_core.c | 20 ++++
>> drivers/vfio/mdev/mdev_private.h | 2 +
>> include/linux/mdev.h | 6 ++
>> include/linux/mdev_virtio_ops.h | 166 +++++++++++++++++++++++++++++++
>> 4 files changed, 194 insertions(+)
>> create mode 100644 include/linux/mdev_virtio_ops.h
>>
>> diff --git a/drivers/vfio/mdev/mdev_core.c b/drivers/vfio/mdev/mdev_core.c
>> index 8d579d7ed82f..95ee4126ff9c 100644
>> --- a/drivers/vfio/mdev/mdev_core.c
>> +++ b/drivers/vfio/mdev/mdev_core.c
>> @@ -76,6 +76,26 @@ const struct mdev_vfio_device_ops *mdev_get_vfio_ops(struct mdev_device *mdev)
>> }
>> EXPORT_SYMBOL(mdev_get_vfio_ops);
>>
>> +/* Specify the virtio device ops for the mdev device, this
>> + * must be called during create() callback for virtio mdev device.
>> + */
> Comment style.
Will fix.
>
>> +void mdev_set_virtio_ops(struct mdev_device *mdev,
>> + const struct mdev_virtio_device_ops *virtio_ops)
>> +{
>> + mdev_set_class(mdev, MDEV_CLASS_ID_VIRTIO);
>> + mdev->virtio_ops = virtio_ops;
>> +}
>> +EXPORT_SYMBOL(mdev_set_virtio_ops);
>> +
>> +/* Get the virtio device ops for the mdev device. */
>> +const struct mdev_virtio_device_ops *
>> +mdev_get_virtio_ops(struct mdev_device *mdev)
>> +{
>> + WARN_ON(mdev->class_id != MDEV_CLASS_ID_VIRTIO);
>> + return mdev->virtio_ops;
>> +}
>> +EXPORT_SYMBOL(mdev_get_virtio_ops);
>> +
>> struct device *mdev_dev(struct mdev_device *mdev)
>> {
>> return &mdev->dev;
>> diff --git a/drivers/vfio/mdev/mdev_private.h b/drivers/vfio/mdev/mdev_private.h
>> index 411227373625..2c74dd032409 100644
>> --- a/drivers/vfio/mdev/mdev_private.h
>> +++ b/drivers/vfio/mdev/mdev_private.h
>> @@ -11,6 +11,7 @@
>> #define MDEV_PRIVATE_H
>>
>> #include <linux/mdev_vfio_ops.h>
>> +#include <linux/mdev_virtio_ops.h>
>>
>> int mdev_bus_register(void);
>> void mdev_bus_unregister(void);
>> @@ -38,6 +39,7 @@ struct mdev_device {
>> u16 class_id;
>> union {
>> const struct mdev_vfio_device_ops *vfio_ops;
>> + const struct mdev_virtio_device_ops *virtio_ops;
>> };
>> };
>>
>> diff --git a/include/linux/mdev.h b/include/linux/mdev.h
>> index 9e37506d1987..f3d75a60c2b5 100644
>> --- a/include/linux/mdev.h
>> +++ b/include/linux/mdev.h
>> @@ -17,6 +17,7 @@
>>
>> struct mdev_device;
>> struct mdev_vfio_device_ops;
>> +struct mdev_virtio_device_ops;
>>
>> /*
>> * Called by the parent device driver to set the device which represents
>> @@ -112,6 +113,10 @@ void mdev_set_class(struct mdev_device *mdev, u16 id);
>> void mdev_set_vfio_ops(struct mdev_device *mdev,
>> const struct mdev_vfio_device_ops *vfio_ops);
>> const struct mdev_vfio_device_ops *mdev_get_vfio_ops(struct mdev_device *mdev);
>> +void mdev_set_virtio_ops(struct mdev_device *mdev,
>> + const struct mdev_virtio_device_ops *virtio_ops);
>> +const struct mdev_virtio_device_ops *
>> +mdev_get_virtio_ops(struct mdev_device *mdev);
>>
>> extern struct bus_type mdev_bus_type;
>>
>> @@ -127,6 +132,7 @@ struct mdev_device *mdev_from_dev(struct device *dev);
>>
>> enum {
>> MDEV_CLASS_ID_VFIO = 1,
>> + MDEV_CLASS_ID_VIRTIO = 2,
>> /* New entries must be added here */
>> };
>>
>> diff --git a/include/linux/mdev_virtio_ops.h b/include/linux/mdev_virtio_ops.h
>> new file mode 100644
>> index 000000000000..0dcae7fa31e5
>> --- /dev/null
>> +++ b/include/linux/mdev_virtio_ops.h
>> @@ -0,0 +1,166 @@
>> +/* SPDX-License-Identifier: GPL-2.0-only */
>> +/*
>> + * Virtio mediated device driver
>> + *
>> + * Copyright 2019, Red Hat Corp.
>> + * Author: Jason Wang <jasowang@...hat.com>
>> + */
>> +#ifndef MDEV_VIRTIO_OPS_H
>> +#define MDEV_VIRTIO_OPS_H
>> +
>> +#include <linux/interrupt.h>
>> +#include <linux/mdev.h>
>> +#include <uapi/linux/vhost.h>
>> +
>> +#define VIRTIO_MDEV_DEVICE_API_STRING "virtio-mdev"
>> +#define VIRTIO_MDEV_F_VERSION_1 0x1
>> +
>> +struct virtio_mdev_callback {
>> + irqreturn_t (*callback)(void *data);
>> + void *private;
>> +};
>> +
>> +/**
>> + * struct mdev_virtio_device_ops - Structure to be registered for each
>> + * mdev device to register the device for virtio/vhost drivers.
>> + *
>> + * The device ops that is supported by VIRTIO_MDEV_F_VERSION_1, the
>> + * callbacks are mandatory unless explicity mentioned.
>> + *
>> + * @get_mdev_features: Get a set of bits that demonstrate
>> + * the capability of the mdev device. New
>> + * feature bits must be added when
>> + * introducing new device ops. This
>> + * allows the device ops to be extended
>> + * (one feature could have N new ops).
>> + * @mdev: mediated device
>> + * Returns the mdev features (API) support by
>> + * the device.
> I still don't see the point of VIRTIO_MDEV_F_VERSION_1. In what case
> would it not be set?
It's a must for current driver implementation.
> What would it indicate to the caller if it were
> not set? The existence of this interface seems to indicate version 1.
The idea is when VIRTIO_MDE_F_VERSION_1 is advertised, driver will
assume all the mandatory callbacks for this feature were implemented.
Then there's no need to check the existence of each callback.
>
> I'm also still unclear how device ops gets extended, can you give some
> examples? Particularly, if feature A and feature B both add device ops
> callbacks, is the vendor allowed to support B but not A, and does that
> imply their device ops structure includes callbacks for A but they're
> unused?
For current API, the answer is yes. So if vendor only support feature B,
it needs to set the device_ops that support feature A to NULL.
> Why doesn't the previous patch take any of this into account
> for struct mdev_vfio_device_ops? I think this is an internal API,
> therefore is it worthwhile to include feature and extension support?
I'm not sure if VFIO has the request. In that case new features could be
extended simply through transport/bus specific way (e.g PCIE capability
list). But in the case of virtio-mdev, we need invent something on our
own. If the simple mapping between features and device ops is proved to
be not sufficient or sub-optimal, we can introduce a more sophisticated
API.
>
>> + * @get_mdev_features: Set a set of features that will be
> s/get/set/
Will fix.
>
>> + * used by the driver.
>> + * @features: features used by the driver
>> + * Returns bollean: whether the features
> s/bollean/boolean/
>
> How does one provide a set of features to set given this prototype?
>
> bool (*set_mdev_feature)(struct mdev_device *mdev);
>
> This is starting to look like a grab bag of callbacks, what sort of
> mdev features would the driver have the ability to set on a device?
Yes, e.g device support A,B,C, but driver will only use B and C.
>
> Note that this is not listed as optional, but the sample driver doesn't
> implement it :-\
My bad, will fix this.
Thanks
> Thanks,
>
> Alex
>
>> + * is accepted by the device.
>> + * @set_vq_address: Set the address of virtqueue
>> + * @mdev: mediated device
>> + * @idx: virtqueue index
>> + * @desc_area: address of desc area
>> + * @driver_area: address of driver area
>> + * @device_area: address of device area
>> + * Returns integer: success (0) or error (< 0)
>> + * @set_vq_num: Set the size of virtqueue
>> + * @mdev: mediated device
>> + * @idx: virtqueue index
>> + * @num: the size of virtqueue
>> + * @kick_vq: Kick the virtqueue
>> + * @mdev: mediated device
>> + * @idx: virtqueue index
>> + * @set_vq_cb: Set the interrupt callback function for
>> + * a virtqueue
>> + * @mdev: mediated device
>> + * @idx: virtqueue index
>> + * @cb: virtio-mdev interrupt callback structure
>> + * @set_vq_ready: Set ready status for a virtqueue
>> + * @mdev: mediated device
>> + * @idx: virtqueue index
>> + * @ready: ready (true) not ready(false)
>> + * @get_vq_ready: Get ready status for a virtqueue
>> + * @mdev: mediated device
>> + * @idx: virtqueue index
>> + * Returns boolean: ready (true) or not (false)
>> + * @set_vq_state: Set the state for a virtqueue
>> + * @mdev: mediated device
>> + * @idx: virtqueue index
>> + * @state: virtqueue state (last_avail_idx)
>> + * Returns integer: success (0) or error (< 0)
>> + * @get_vq_state: Get the state for a virtqueue
>> + * @mdev: mediated device
>> + * @idx: virtqueue index
>> + * Returns virtqueue state (last_avail_idx)
>> + * @get_vq_align: Get the virtqueue align requirement
>> + * for the device
>> + * @mdev: mediated device
>> + * Returns virtqueue algin requirement
>> + * @get_features: Get virtio features supported by the device
>> + * @mdev: mediated device
>> + * Returns the virtio features support by the
>> + * device
>> + * @set_features: Set virtio features supported by the driver
>> + * @mdev: mediated device
>> + * @features: feature support by the driver
>> + * Returns integer: success (0) or error (< 0)
>> + * @set_config_cb: Set the config interrupt callback
>> + * @mdev: mediated device
>> + * @cb: virtio-mdev interrupt callback structure
>> + * @get_vq_num_max: Get the max size of virtqueue
>> + * @mdev: mediated device
>> + * Returns u16: max size of virtqueue
>> + * @get_device_id: Get virtio device id
>> + * @mdev: mediated device
>> + * Returns u32: virtio device id
>> + * @get_vendor_id: Get id for the vendor that provides this device
>> + * @mdev: mediated device
>> + * Returns u32: virtio vendor id
>> + * @get_status: Get the device status
>> + * @mdev: mediated device
>> + * Returns u8: virtio device status
>> + * @set_status: Set the device status
>> + * @mdev: mediated device
>> + * @status: virtio device status
>> + * @get_config: Read from device specific configuration space
>> + * @mdev: mediated device
>> + * @offset: offset from the beginning of
>> + * configuration space
>> + * @buf: buffer used to read to
>> + * @len: the length to read from
>> + * configration space
>> + * @set_config: Write to device specific configuration space
>> + * @mdev: mediated device
>> + * @offset: offset from the beginning of
>> + * configuration space
>> + * @buf: buffer used to write from
>> + * @len: the length to write to
>> + * configration space
>> + * @get_generation: Get device config generaton (optional)
>> + * @mdev: mediated device
>> + * Returns u32: device generation
>> + */
>> +struct mdev_virtio_device_ops {
>> + /* Mdev device ops */
>> + u64 (*get_mdev_features)(struct mdev_device *mdev);
>> + bool (*set_mdev_feature)(struct mdev_device *mdev);
>> + /* Virtqueue ops */
>> + int (*set_vq_address)(struct mdev_device *mdev,
>> + u16 idx, u64 desc_area, u64 driver_area,
>> + u64 device_area);
>> + void (*set_vq_num)(struct mdev_device *mdev, u16 idx, u32 num);
>> + void (*kick_vq)(struct mdev_device *mdev, u16 idx);
>> + void (*set_vq_cb)(struct mdev_device *mdev, u16 idx,
>> + struct virtio_mdev_callback *cb);
>> + void (*set_vq_ready)(struct mdev_device *mdev, u16 idx, bool ready);
>> + bool (*get_vq_ready)(struct mdev_device *mdev, u16 idx);
>> + int (*set_vq_state)(struct mdev_device *mdev, u16 idx, u64 state);
>> + u64 (*get_vq_state)(struct mdev_device *mdev, u16 idx);
>> +
>> + /* Virtio device ops */
>> + u16 (*get_vq_align)(struct mdev_device *mdev);
>> + u64 (*get_features)(struct mdev_device *mdev);
>> + int (*set_features)(struct mdev_device *mdev, u64 features);
>> + void (*set_config_cb)(struct mdev_device *mdev,
>> + struct virtio_mdev_callback *cb);
>> + u16 (*get_vq_num_max)(struct mdev_device *mdev);
>> + u32 (*get_device_id)(struct mdev_device *mdev);
>> + u32 (*get_vendor_id)(struct mdev_device *mdev);
>> + u8 (*get_status)(struct mdev_device *mdev);
>> + void (*set_status)(struct mdev_device *mdev, u8 status);
>> + void (*get_config)(struct mdev_device *mdev, unsigned int offset,
>> + void *buf, unsigned int len);
>> + void (*set_config)(struct mdev_device *mdev, unsigned int offset,
>> + const void *buf, unsigned int len);
>> + u32 (*get_generation)(struct mdev_device *mdev);
>> +};
>> +
>> +void mdev_set_virtio_ops(struct mdev_device *mdev,
>> + const struct mdev_virtio_device_ops *virtio_ops);
>> +
>> +#endif
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