Re: [Xen-devel] qemu and xl semantics

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

On Fri, 2010-12-17 at 09:00 +0000, Christoph Egger wrote:
> Hi!
> 
> When I start a guest with xm  the disk startup script assigns a loopback 
> device for qemu to open it.
> 
> Now it seems that qemu opens the disk image directly. Then when
> the loopback device wants to open the disk image then that fails
> with EBUSY.

By "Now..." you mean "With xl..." ?

> How is the disk startup script supposed to work with the new
> semantic for
> a) HVM guests
> b) PV guests
> ?

I think this is all very specific to the precise disk type you have in
your config, i.e. tap: vs file: vs phy: etc. Which are you using?

> 
> The network startup script adds the tap device to the bridge
> or assigns an ip address.
> With xl neither the disk nor the network script runs.
> So when I start the guest with xl then I have
> the tap device assigned to the guest but the
> tap device is not configured in the dom0.
> 
> How does the 'xl' way work in respect to the network script
> used with 'xm' ?

On Linux these are run from the hotplug event, via the udev rules. I
presume you are talking about on NetBSD though?

Under Linux I think it was always the same under xm too although there
have been some tweaks recently, e.g. the vif script is now always
/etc/xen/scripts/vif-setup which handles the indirection to the script
in the domain config or the default. Previously xend the hotplug rules
called the configured script directly. This change was
21549:8bcaec29574e and was common to xm and xl I think.

Ian.


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