linux-kernel - Re: [PATCH V9 5/6] virtio: introduce a mdev based transport

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Message-ID: <20191106120047.5bcf49c3.cohuck@redhat.com>
Date:   Wed, 6 Nov 2019 12:00:47 +0100
From:   Cornelia Huck <cohuck@...hat.com>
To:     Jason Wang <jasowang@...hat.com>
Cc:     kvm@...r.kernel.org, linux-s390@...r.kernel.org,
        linux-kernel@...r.kernel.org, dri-devel@...ts.freedesktop.org,
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        alex.williamson@...hat.com, mst@...hat.com, tiwei.bie@...el.com,
        virtualization@...ts.linux-foundation.org, netdev@...r.kernel.org,
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Subject: Re: [PATCH V9 5/6] virtio: introduce a mdev based transport

On Wed,  6 Nov 2019 15:05:47 +0800
Jason Wang <jasowang@...hat.com> wrote:

> This patch introduces a new mdev transport for virtio. This is used to
> use kernel virtio driver to drive the mediated device that is capable
> of populating virtqueue directly.
> 
> A new virtio-mdev driver will be registered to the mdev bus, when a
> new virtio-mdev device is probed, it will register the device with
> mdev based config ops. This means it is a software transport between
> mdev driver and mdev device. The transport was implemented through
> device specific ops which is a part of mdev_parent_ops now.
> 
> Signed-off-by: Jason Wang <jasowang@...hat.com>
> ---
>  drivers/virtio/Kconfig       |  13 ++
>  drivers/virtio/Makefile      |   1 +
>  drivers/virtio/virtio_mdev.c | 406 +++++++++++++++++++++++++++++++++++
>  3 files changed, 420 insertions(+)
>  create mode 100644 drivers/virtio/virtio_mdev.c
> 
> diff --git a/drivers/virtio/Kconfig b/drivers/virtio/Kconfig
> index 078615cf2afc..558ac607d107 100644
> --- a/drivers/virtio/Kconfig
> +++ b/drivers/virtio/Kconfig
> @@ -43,6 +43,19 @@ config VIRTIO_PCI_LEGACY
>  
>  	  If unsure, say Y.
>  
> +config VIRTIO_MDEV
> +	tristate "MDEV driver for virtio devices"
> +	depends on VFIO_MDEV && VIRTIO
> +	default n
> +	help
> +	  This driver provides support for virtio based paravirtual
> +	  device driver over MDEV bus. This requires your environemnt
> +	  has appropriate virtio mdev device implementation which may
> +	  operate on the physical device that the datapath of virtio
> +	  could be offloaded to hardware.

That sentence is a bit confusing to me... what about

"For this to be useful, you need an appropriate virtio mdev device
implementation that operates on a physical device to allow the datapath
of virtio to be offloaded to hardware."

?

> +
> +	  If unsure, say M

Building this as a module should not hurt (but please add a trailing
'.' here :)

> +
>  config VIRTIO_PMEM
>  	tristate "Support for virtio pmem driver"
>  	depends on VIRTIO

With the changes above,

Reviewed-by: Cornelia Huck <cohuck@...hat.com>