Re: [Xen-devel] [PATCH] Solved the Xen PV/KASLR riddle

From: Jan Beulich
Date: Fri Aug 29 2014 - 10:44:14 EST

>>> On 29.08.14 at 16:27, <stefan.bader@xxxxxxxxxxxxx> wrote:
> Sure. Btw, someone also contacted me saying they have the same problem
> without
> changing the layout but having really big initrd (500M). While that feels
> like
> it should be impossible (if the kernel+initrd+xen stuff has to fix the 512M
> kernel image size area then). But if it can happen, then surely it does
> cause
> mappings to be where the module space starts then.

Since the initrd doesn't really need to be mapped into the (limited)
virtual address space a pv guest starts with, we specifically got

* Whether or not the guest can deal with being passed an initrd not
* mapped through its initial page tables.

to deal with that situation. The hypervisor side for Dom0 is in place,
and the kernel side works in our (classic) kernels. Whether it got
implemented for DomU meanwhile I don't know; I'm pretty certain
pv-ops kernels don't support it so far.


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