Re: Xen PV: Sample new PV driver for buffer sharing between domains

[Juergen Gross <jgross@suse.com>]

On 27/09/2018 12:35, Omkar Bolla wrote:
> Hi,
> 
> Sorry, I forgot, I used code from github chapter [2] from that link, and
> I just changed name "mydevice"  to "vdevb"

Okay.

> 
>> Error 13 is EACCESS. I guess the access rights of the Xenstore nodes
>> are not sufficient to write the needed entries.
> Where I have to provide access rights, i.e from Kernel code or from from
> command line in domain-0 or modify in xen source?

I guess you have your frontend already loaded when running the
script creating the Xenstore entries?

This would explain the problem: as soon as the entries are written
the frontend will react. At this point the access rights are not setup
properly, this is done a little bit later in the script.

Possible solutions are to either load the frontend driver only after
setting up the Xenstore entries, or to pause the domain while doing
so and unpause it afterwards (or start the domain paused, create the
Xenstore entries, and unpause the domain).

The really correct way to do it would be to setup Xenstore in a single
transaction (write all the entries and set access rights).

> Any thing that I have to do/change in xenbits xen-4.8 sources code, to
> add new PV device?

Only if you want to include domain config file entries for your device.

> 
>> Did you modify Xen tools (xl/libxl) for adding the new device type?
> No, is it needed to modify some thing in xl/libxl for adding new device
> type?

This was just a question to learn how Xenstore is being initialized
in your scenario.

> 
>> If not you need to setup the Xenstore nodes manually.
> Setup manually Xenstore means, using commands?

Yes, like your script does.


Juergen

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