Re: [Xen-API] xapi toolstack

[Daniel Stodden <daniel.stodden@xxxxxxxxxx>]

On Tue, 2010-02-23 at 16:35 -0500, Ritu kaur wrote:
> Hi,

Hey Ritu.

> Its my understanding that virtual interfaces(vif, vbd...) are created
> by xapi toolstack when a vm is installed i.e basically xapi toolstack
> controls creation/deletion of interfaces in dom0 when VM's come and
> go. Is it true that xapi toolstack runs in domU as well since
> interfaces are created there for netfront drivers?

The creation is managed via xenstore. There are xenbus clients in the
guest OS, as there is one dom0.

Actually dom0 and Linux domUs share basically the same code, because
frontends and backends are quite similar. Look into drivers/xen/xenbus/.

So xapi in dom0 userland also communicates with domU kernels. It
creates /local/domain/<domid>/device/<type> nodes, and writes all fields
necessary to get them initialized. 

The .probe and .remove function you saw in the xenbus_driver struct are
called when these xenstore directories are created and removed,
respectively.

> If I were to create a temp device
> under /sys/bus/xen-backend/devices/(this is where I see vif, vbd and
> other devices are present in dom0), I believe I have to modify xapi
> toolstack is that correct?

The xen-backend sysfs class only represents the kernel space components.
The ones you find in drivers/xen. 

Any instance of these drivers, once created via xenstore, is represented
by some device node in the kernel. These correspond to the nodes you
find in sysfs.

Code to control them via xenstore would belong into the toolstack.

Daniel




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