Xen, and "ops_pv" boot loader?
Dr Josef Karthauser
joe at tao.org.uk
Fri Mar 4 14:22:19 UTC 2011
I'm beginning to play with Freebsd and Xen, and I'm targeting a VPS provider who is giving me a large memory instance for a good price. However, he only supports "ops_pv" kernels, being primarily a linux house.
So, I'm trying to work out what the best approach is. Ideally I'd be running amd64, but he doesn't want to run an hvmloader. I guess that means that I need to be running an i386 kernel; hopefully PAE works so that I take advantage of the memory.
However, this appears to be an inflexible solution. Doesn't it mean that I will have no ability to tweak kernel variables, because effectively once it's setup he will control the boot process - I'll also not be able to upgrade the kernel easily. Also, no access to single user mode... Ideally I want a boot loader....
So, I was thinking. How do we make the boot loader appear to Xen to be a paravirtualized kernel? Currently it isn't even an elf object, but what it is was. How much work do you think that it might be to make a "loader kernel" that appears to be a kernel, but in fact is a boot strap. The idea being that it could be run as a "ops_pv" kernel on a Xen platform but otherwise behave exactly like our boot loader, processing loader.conf, and booting a kernel in the normal way.
Does anyone have any idea of whether that's a possibility? Or, is there something fundamental about the pv_ops model that would prevent this?
If this were possible we could boot the amd64 XENHVM kernel in a pv_ops manner, with full control of the kernel configuration.
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