Xen devel - Nov 2011 - pvgrub --> kexec

Good day.

Right now we have pvgrub and pygrub as loaders. Pygrub is more mature, 
pvgrub is safer and  more ''right'' stuff to have.

But even the pvgrub is still have one real problem: we need to write our 
own domU operating system with support of bunch of filesystems, hardly 
to create interactivity, limited network capabilities (...yep, I can be 
nice to have networking at boot time).

How about different approach? If we run linux with specially crafted 
initrd, which will look around, see correct partition, mount it (in 
domU!), get kernel, show menu, do networking and prepare the coffee for 
admin.  After that it will to kexec to found kernel with found initrd 
with required argument.

No any dangerous dom0 manipulation with VDI, no more modules 
synchronization problem (in case ''external'' kernel loading).
Easy to
create menus (just any ncurses application), ideal pre-boot 
configuration environment for appliances (I ask user about settings and 
boot real kernel with asked parameters).

The single problem: kexec is not supporting xen.

On Sat, Nov 19, 2011 at 07:38:50AM +0400, George Shuklin
wrote:
> Good day.
>
> Right now we have pvgrub and pygrub as loaders. Pygrub is more mature,
> pvgrub is safer and  more ''right'' stuff to have.
>
> But even the pvgrub is still have one real problem: we need to write our
> own domU operating system with support of bunch of filesystems, hardly
> to create interactivity, limited network capabilities (...yep, I can be
> nice to have networking at boot time).
>
> How about different approach? If we run linux with specially crafted
> initrd, which will look around, see correct partition, mount it (in
> domU!), get kernel, show menu, do networking and prepare the coffee for
> admin.  After that it will to kexec to found kernel with found initrd
> with required argument.
>
> No any dangerous dom0 manipulation with VDI, no more modules
> synchronization problem (in case ''external'' kernel
loading). Easy to
> create menus (just any ncurses application), ideal pre-boot
> configuration environment for appliances (I ask user about settings and
> boot real kernel with asked parameters).
>
> The single problem: kexec is not supporting xen.
kexec/kdump is partialy supported by Xen. Xenlinux Ver. 2.6.18
supports kexec/kdump in dom0. As I know Olaf Hering works (still ???)
on support for kexec/kdump for PV-on-HVM domains. Currently my work
focuses on kexec/kdump support for domU for Xenlinux Ver. 2.6.18.
Later it will be ported to mainline kernel. I am going to publish
this about Feb 2012. Additionally, I am going to prepare kexec/kdump
support for dom0 for mainline kernel.

Daniel