WARNING - OLD ARCHIVES

This is an archived copy of the Xen.org mailing list, which we have preserved to ensure that existing links to archives are not broken. The live archive, which contains the latest emails, can be found at http://lists.xen.org/
   
 
 
Xen 
 
Home Products Support Community News
 
   
 

xen-devel

Re: [Xen-devel] Strange (???) xl behavior for save, migrate and migrate-

On Tue, Oct 18, 2011 at 09:19:01AM +0100, Ian Campbell wrote:
> On Mon, 2011-10-17 at 19:44 +0100, Dan Magenheimer wrote:
> > In a recent internal discussion at Oracle, we were thinking about
> > whether to enable hotplug functionality in a guest kernel and it
> > raised some concerns about manageability.  I think right now
> > the system administrator of the guest can arbitrarily increase
> > memory size beyond maxmem...
>
> The memory limit for a guest is ultimately controlled by the host
> administrator/toolstack. The in-guest admin cannot exceed that, even
> using hotplug.

Correct.

> I think that limit is currently always set to the current balloon target.

Nope. It is set by maxmem option.

> AIUI Daniel's work only allows a guest admin to take advantage of new
> memory above maxmem _after_ the host admin has provisioned that RAM to
> the guest. IOW it only allows the guest to take advantage of new memory
> given to it and does not allow the guest to acquire new memory of its
> own accord.

Guest/host administartor could allocate for given guest no more memory than
maxmem (its value could be changed by xl mem-max <domain> <new_size>) allows,
regardless of mechanism (ballooning or memory hotplug) used for that allocation.
It means that memory hotplug does not pose any security threat in that area.

Daniel

_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxxxxxxxx
http://lists.xensource.com/xen-devel