Re: Hotplugged devices in Xen 4.5 and domain reboot

[Wei Liu <wei.liu2@citrix.com>]

On Tue, Dec 01, 2015 at 03:24:13PM +0200, Pavlo Suikov wrote:
> Hi,
> 
> got a question regarding hotplugged devices in Xen 4.5. What we currently
> have is Xen 4.5, Linux in Dom0 and DomD and Android in DomU. All the
> devices are configured via domain config, so they are initialized on domain
> startup: libxl reads config, sets up xenstore branches and fills them for
> driver back ends and front ends; front ends monitor these branches and fill
> in their specific data once connection is established. On DomU reboot,
> config is being re-read and all the devices are started again in the same
> manner.
> 
> Problem is we don't really know what to do with hotplugged devices. When
> such a device appears in DomU during runtime, we set up all the xenstore
> insformation on the fly, but it doesn't go to persistent domain
> configuration; so when DomU reboot comes, they are not set up again as they
> should. All the solutions we are considering look like dirty hacks (e.g.
> making separate branch in xenstore for hotplugged devices, reading it on
> domain start in the same way domain config is parsed, and copying data to
> corresponding xenstore domain branches). Are there any existing ways to
> handle these?
> 

Do you have the exact runes you use to do the hotplug? How do you reboot
your DomU? What does /var/lib/xen/userdata-d.$DOMID-$UUID.libxl-json
look like before and after hotplug?

Wei.

> Suikov Pavlo
> GlobalLogic
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