Re: [Xen-devel] What's the benefit and design purpose of Xen Console for HVM guest.

[Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>]

On Fri, 29 Mar 2013, Wei Xu wrote:
> Hi guys,
> I'm investigating Xen Console recently, i take some test on Linux(Fedora) hvm 
> guest, it works good. (Xen-4.1.3 and Linux 3.5.0)
> 
> As far as i know, the performance improvement of Xen Console seems to be 
> great, but it looks like it just provides a shell for
> login via Xen Console for function concern, since it's a console,
> i wonder if it is designed to be a system console? or just an additional 
> shell access to the guest like ssh(rlogin), that means
> is it able to replace the emulated serial by qemu-dm totally, can it be able 
> to print the early boot message and debugging
> message generated by printk() like function? Â

Yes, you just need to pass console=hvc0 to the kernel command line.
It's not just useful for debugging, it's also possible to add a large
number of PV consoles to an HVM guest, and they should all work without
issues: one could be only used for logging kernel messages for example,
another one for logging something else, and the rest as login shells.
At the moment xl doesn't export a config option to do that, but libxl
knows how to create as many PV console as you like.

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