Paravitrualization drivers query

Paravitrualization drivers query

[shishir tiwari]

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Hi

I am trying understand Xen Pv drivers and i writing my own pv fronend and
backend driver.

1. For driver internal communication how do i create/write node in backend
driver and how to read in fronted drivers.
2.how do i create one shared page in backend driver to write/read data in
frontend driver.

I gone-through kernel code and but its tittle bit confusing to me.

someone share set api for this it would help me lot.





Thanks
Shishir tiwari

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Re: Paravitrualization drivers query

[Wei Liu]

On Thu, Jul 20, 2017 at 08:29:48PM +0530, shishir tiwari wrote:
> Hi
> 
> I am trying understand Xen Pv drivers and i writing my own pv fronend and
> backend driver.
> 
> 1. For driver internal communication how do i create/write node in backend
> driver and how to read in fronted drivers.
> 2.how do i create one shared page in backend driver to write/read data in
> frontend driver.
> 

Depending on where your driver lives (kernel or userspace), the APIs are
going to be different.

> I gone-through kernel code and but its tittle bit confusing to me.

Which bits do you find confusing?

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Re: Paravitrualization drivers query

[shishir tiwari]

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> Hi
>
> I am trying understand Xen Pv drivers and i writing my own pv fronend and
> backend driver.
>
> 1. For driver internal communication how do i create/write node in backend
> driver and how to read in fronted drivers.
> 2.how do i create one shared page in backend driver to write/read data in
> frontend driver.
>

>Depending on where your driver lives >(kernel or userspace), the APIs are
>going to be different.


My driver will be in kernel space. I want to create some Node and shared
page or queue. So I can transfer data for domu to dom0.


> I gone-through kernel code and but its tittle bit confusing to me.

>>Which bits do you find confusing?


I am not able to understand who first create Node and shared memory by xen
or domO or may be by frontend drivers

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Re: Paravitrualization drivers query

[Dongli Zhang]

On 07/21/2017 03:12 PM, shishir tiwari wrote:
> 
>     > Hi
>     >
>     > I am trying understand Xen Pv drivers and i writing my own pv fronend and
>     > backend driver.
>     >
>     > 1. For driver internal communication how do i create/write node in backend
>     > driver and how to read in fronted drivers.
>     > 2.how do i create one shared page in backend driver to write/read data in
>     > frontend driver.
>     >
> 
>     >Depending on where your driver lives >(kernel or userspace), the APIs are
>     >going to be different.
> 
> 
> My driver will be in kernel space. I want to create some Node and shared page or
> queue. So I can transfer data for domu to dom0. 

Hi Shishir

I suggest you read about drivers/net/xen-netfront.c and
drivers/net/xen-netback/* in linux kernel.

You would rely on xenbus/xenstore to read/write node in frontend or backend and
the corresponding APIs are xenbus_write, xenbus_printf, xenbus_read, etc.

To create shared page between frontend and backend, you create use grant tale
mechanism. Generally, each grant table reference is used to indicate one shared
memory page. The frontend allocates a page to share and bind this page to a
grant table reference. This reference is then passed to backend via xenstore or
ring buffer. Backend maps the shared page with this reference via APIs like
gnttab_map_refs().

I suggest you read about the book "Definitive Guide to Xen Hypervisor" and read
about linux paravirtual driver code.

Dongli Zhang

> 
> 
>     > I gone-through kernel code and but its tittle bit confusing to me.
> 
>     >>Which bits do you find confusing?
> 
> 
> I am not able to understand who first create Node and shared memory by xen or
> domO or may be by frontend drivers
> 
> 
> 
> 
> _______________________________________________
> Xen-devel mailing list
> Xen-devel@lists.xen.org
> https://lists.xen.org/xen-devel
> 

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Re: Paravitrualization drivers query

[Wei Liu]

On Fri, Jul 21, 2017 at 12:42:04PM +0530, shishir tiwari wrote:
> > Hi
> >
> > I am trying understand Xen Pv drivers and i writing my own pv fronend and
> > backend driver.
> >
> > 1. For driver internal communication how do i create/write node in backend
> > driver and how to read in fronted drivers.
> > 2.how do i create one shared page in backend driver to write/read data in
> > frontend driver.
> >
> 
> >Depending on where your driver lives >(kernel or userspace), the APIs are
> >going to be different.
> 
> 
> My driver will be in kernel space. I want to create some Node and shared
> page or queue. So I can transfer data for domu to dom0.
> 
> 
> > I gone-through kernel code and but its tittle bit confusing to me.
> 
> >>Which bits do you find confusing?
> 
> 
> I am not able to understand who first create Node and shared memory by xen
> or domO or may be by frontend drivers

The nodes are first created by the toolstack, then filled in by backend
and frontend.

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