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Subject: Re: [PATCH V4 4/6] mdev: introduce virtio device and its device ops
To:     Cornelia Huck <cohuck@redhat.com>
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References: <20191017104836.32464-1-jasowang@redhat.com>
 <20191017104836.32464-5-jasowang@redhat.com>
 <20191018114614.6f1e79dc.cohuck@redhat.com>
From:   Jason Wang <jasowang@redhat.com>
Message-ID: <733c0cfe-064f-c8ba-6bf8-165db88d7e07@redhat.com>
Date:   Fri, 18 Oct 2019 18:55:02 +0800
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On 2019/10/18 下午5:46, Cornelia Huck wrote:
> On Thu, 17 Oct 2019 18:48:34 +0800
> Jason Wang <jasowang@redhat.com> wrote:
>
>> This patch implements basic support for mdev driver that supports
>> virtio transport for kernel virtio driver.
>>
>> Signed-off-by: Jason Wang <jasowang@redhat.com>
>> ---
>>   drivers/vfio/mdev/mdev_core.c |  12 +++
>>   include/linux/mdev.h          |   4 +
>>   include/linux/virtio_mdev.h   | 151 ++++++++++++++++++++++++++++++++++
>>   3 files changed, 167 insertions(+)
>>   create mode 100644 include/linux/virtio_mdev.h
>>
>> diff --git a/drivers/vfio/mdev/mdev_core.c b/drivers/vfio/mdev/mdev_core.c
>> index d0f3113c8071..5834f6b7c7a5 100644
>> --- a/drivers/vfio/mdev/mdev_core.c
>> +++ b/drivers/vfio/mdev/mdev_core.c
>> @@ -57,6 +57,18 @@ void mdev_set_vfio_ops(struct mdev_device *mdev,
>>   }
>>   EXPORT_SYMBOL(mdev_set_vfio_ops);
>>   
>> +/* Specify the virtio device ops for the mdev device, this
>> + * must be called during create() callback for virtio mdev device.
>> + */
> Change this as for the vfio comment (last patch?)


Ok.


>
>> +void mdev_set_virtio_ops(struct mdev_device *mdev,
>> +			 const struct virtio_mdev_device_ops *virtio_ops)
>> +{
>> +	BUG_ON(mdev->class_id);
> s/BUG_ON/WARN_ON/


Yes.


>
>> +	mdev->class_id = MDEV_CLASS_ID_VIRTIO;
>> +	mdev->device_ops = virtio_ops;
>> +}
>> +EXPORT_SYMBOL(mdev_set_virtio_ops);
>> +
>>   const void *mdev_get_dev_ops(struct mdev_device *mdev)
>>   {
>>   	return mdev->device_ops;
> (...)
>
>> diff --git a/include/linux/virtio_mdev.h b/include/linux/virtio_mdev.h
>> new file mode 100644
>> index 000000000000..b965b50f9b24
>> --- /dev/null
>> +++ b/include/linux/virtio_mdev.h
>> @@ -0,0 +1,151 @@
>> +/* 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_F_VERSION_1 0x1
>> +
>> +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)
> Probably dumb question (have not read the next patches yet): Is this
> agnostic regarding split or packed queues?


Yes, it is to and to be more obvious, I use the terminology from recent 
spec.


>
>> + * @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
>> + * @get_features:		Set virtio features supported by the driver
> s/get_features/set_features/


Will fix.


>
>> + *				@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 virtio vendor id
>> + *				@mdev: mediated device
>> + *				Returns u32: virtio vendor id
> How is the vendor id defined? As for normal virtio-pci devices?


The vendor that provides this device. So something like this

I notice that MMIO also had this so it looks to me it's not pci specific.


>
>> + * @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_mdev_features:		Get the feature of virtio mdev device
>> + *				@mdev: mediated device
>> + *				Returns the mdev features (API) support by
>> + *				the device.
> What kind of 'features' are supposed to go in there? Are these bits,
> like you defined for VIRTIO_MDEV_F_VERSION_1 above?


It's the API or mdev features other than virtio features. It could be 
used by driver to determine the capability of the mdev device. Besides 
_F_VERSION_1, we may add dirty page tracking etc which means we need new 
device ops.


>
>> + * @get_generation:		Get device generaton
>> + *				@mdev: mediated device
>> + *				Returns u32: device generation
> Is that callback mandatory?


I think so, it's hard to emulate that completely in virtio-mdev transport.

Thanks


>
>> + */
>> +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_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);
>> +	u64 (*get_mdev_features)(struct mdev_device *mdev);
>> +	u32 (*get_generation)(struct mdev_device *mdev);
>> +};
>> +
>> +void mdev_set_virtio_ops(struct mdev_device *mdev,
>> +			 const struct virtio_mdev_device_ops *virtio_ops);
>> +
>> +#endif