Re: [PATCH V2 6/8] mdev: introduce virtio device and its device ops

From: Jason Wang <jasowang@redhat.com>
To: "Michael S. Tsirkin" <mst@redhat.com>
Cc: "christophe.de.dinechin@gmail.com"
	<christophe.de.dinechin@gmail.com>,
	"kvm@vger.kernel.org" <kvm@vger.kernel.org>,
	"airlied@linux.ie" <airlied@linux.ie>,
	"heiko.carstens@de.ibm.com" <heiko.carstens@de.ibm.com>,
	"farman@linux.ibm.com" <farman@linux.ibm.com>,
	"dri-devel@lists.freedesktop.org"
	<dri-devel@lists.freedesktop.org>,
	"virtualization@lists.linux-foundation.org"
	<virtualization@lists.linux-foundation.org>,
	"kwankhede@nvidia.com" <kwankhede@nvidia.com>,
	"rob.miller@broadcom.com" <rob.miller@broadcom.com>,
	"linux-s390@vger.kernel.org" <linux-s390@vger.kernel.org>,
	"sebott@linux.ibm.com" <sebott@linux.ibm.com>,
	"lulu@redhat.com" <lulu@redhat.com>,
	"eperezma@redhat.com" <eperezma@redhat.com>,
	"pasic@linux.ibm.com" <pasic@linux.ibm.com>,
	"borntraeger@de.ibm.com" <borntraeger@de.ibm.com>,
	"haotian.wang@sifive.com" <haotian.wang@sifive.com>,
	"Liang, Cunming" <cunming>
Subject: Re: [PATCH V2 6/8] mdev: introduce virtio device and its device ops
Date: Thu, 26 Sep 2019 12:04:46 +0800	[thread overview]
Message-ID: <eb7c76b5-2938-2e73-d847-b174a289c5c9@redhat.com> (raw)
In-Reply-To: <20190925092044-mutt-send-email-mst@kernel.org>

On 2019/9/25 下午9:21, Michael S. Tsirkin wrote:
> On Wed, Sep 25, 2019 at 08:45:21PM +0800, Jason Wang wrote:
>> On 2019/9/25 下午5:09, Tian, Kevin wrote:
>>>> From: Jason Wang [mailto:jasowang@redhat.com]
>>>> Sent: Tuesday, September 24, 2019 9:54 PM
>>>>
>>>> This patch implements basic support for mdev driver that supports
>>>> virtio transport for kernel virtio driver.
>>>>
>>>> Signed-off-by: Jason Wang<jasowang@redhat.com>
>>>> ---
>>>>    include/linux/mdev.h        |   2 +
>>>>    include/linux/virtio_mdev.h | 145
>>>> ++++++++++++++++++++++++++++++++++++
>>>>    2 files changed, 147 insertions(+)
>>>>    create mode 100644 include/linux/virtio_mdev.h
>>>>
>>>> diff --git a/include/linux/mdev.h b/include/linux/mdev.h
>>>> index 3414307311f1..73ac27b3b868 100644
>>>> --- a/include/linux/mdev.h
>>>> +++ b/include/linux/mdev.h
>>>> @@ -126,6 +126,8 @@ struct mdev_device *mdev_from_dev(struct device
>>>> *dev);
>>>>
>>>>    enum {
>>>>    	MDEV_ID_VFIO = 1,
>>>> +	MDEV_ID_VIRTIO = 2,
>>>> +	MDEV_ID_VHOST = 3,
>>>>    	/* New entries must be added here */
>>>>    };
>>>>
>>>> diff --git a/include/linux/virtio_mdev.h b/include/linux/virtio_mdev.h
>>>> new file mode 100644
>>>> index 000000000000..d1a40a739266
>>>> --- /dev/null
>>>> +++ b/include/linux/virtio_mdev.h
>>>> @@ -0,0 +1,145 @@
>>>> +/* SPDX-License-Identifier: GPL-2.0-only */
>>>> +/*
>>>> + * Virtio mediated device driver
>>>> + *
>>>> + * Copyright 2019, Red Hat Corp.
>>>> + *     Author: Jason Wang<jasowang@redhat.com>
>>>> + */
>>>> +#ifndef _LINUX_VIRTIO_MDEV_H
>>>> +#define _LINUX_VIRTIO_MDEV_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_VERSION 0x1
>>> Just be curious. is this version identical to virtio spec version that below
>>> callbacks are created for, or just irrelevant?
>> It could be a hint but basically it's a way for userspace driver
>> compatibility. For kernel we don't need this.
>>
>>
>>>> +
>>>> +struct virtio_mdev_callback {
>>>> +	irqreturn_t (*callback)(void *data);
>>>> +	void *private;
>>>> +};
>>>> +
>>>> +/**
>>>> + * struct vfio_mdev_device_ops - Structure to be registered for each
>>>> + * mdev device to register the device to virtio-mdev module.
>>>> + *
>>>> + * @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 interrut calback 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 features support by the
>>>> + *				device
>>>> + * @get_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_device_id:		Get virtio device id
>>>> + *				@mdev: mediated device
>>>> + *				Returns u32: virtio device id
>>>> + * @get_vendor_id:		Get virtio vendor id
>>>> + *				@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 confiugration
>>>> space
>>> configuration (and similar typos downward)
>> Let me fix.
>>
>>
>>>> + *				@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 confiugration 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_version:		Get the version of virtio mdev device
>>>> + *				@mdev: mediated device
>>>> + *				Returns integer: version of the device
>>>> + * @get_generation:		Get device generaton
>>>> + *				@mdev: mediated device
>>>> + *				Returns u32: device generation
>>>> + */
>>>> +struct virtio_mdev_device_ops {
>>>> +	/* 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);
>>>> +
>>>> +	/* 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_queue_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);
>>>> +	int (*get_version)(struct mdev_device *mdev);
>>>> +	u32 (*get_generation)(struct mdev_device *mdev);
>>>> +};
>>> I'm not sure how stable above ops are.
>> It's the kernel internal API, so there's no strict requirement for this. We
>> will export a version value for userspace for compatibility.
> Given it's tied to virtio we probably want kernel+userspace
> feature bits?

Yes, then I think we could probably have a version field inside e.g 
device_ops structure. Then it could be fetched from both kernel and 
userspace driver.

Thanks

>
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