Re: [Xen-devel] [PATCH 2/2] x86/xen: dont add memory above max allowed allocation

[Juergen Gross]

On 22/01/2019 09:52, Jan Beulich wrote:
>>>> On 22.01.19 at 09:06, <jgross@xxxxxxxx> wrote:
>> Don't allow memory to be added above the allowed maximum allocation
>> limit set by Xen.
> 
> This reads as if the hypervisor was imposing a limit here, but looking at
> xen_get_max_pages(), xen_foreach_remap_area(), and
> xen_count_remap_pages() I take it that it's a restriction enforced by
> the Xen subsystem in Linux. Furthermore from the cover letter I imply
> that the observed issue was on a Dom0, yet xen_get_max_pages()'s
> use of XENMEM_maximum_reservation wouldn't impose any limit there
> at all (without use of the hypervisor option "dom0_mem=max:..."),
> would it?

Oh yes, you are right, of course!

I need to check the current reservation and adjust the allowed limit
in case of ballooning and/or memory hotplug.

Thanks for noticing that!


Juergen