Re: [Xen-devel] [PATCH] Make ballooning work with maxmem > mem (i386 version)

[Glauber de Oliveira Costa <gcosta@xxxxxxxxxx>]

On Fri, Nov 10, 2006 at 03:23:15PM +0000, Keir Fraser wrote:
> On 10/11/06 13:24, "Glauber de Oliveira Costa" <gcosta@xxxxxxxxxx> wrote:
> 
> > Trying to start a guest with maxmem > mem and then balloon up to a value
> > greater than mem is currently failing. This have been already discovered
> > (patch sent some days ago) for x86_64. i386 suffers from the same
> > problem.
> > 
> > This patch fixes it.
> 
> I took both patches and then changed my mind and immediately reverted them.
> There is a better way: we should support the XENMEM_memory_map hypercall.
> We should provide a hypercall (domctl) to set a memory_map_limit parameter
> and then Xen can use that to fake a memory map when XENMEM_memory_map is
> called. The tools can set that parameter from config['maxmem'].

And what happens when the hypercall ever returns ENOSYS, like a kernel
running in a bit old Hypervisor? 

IMHO,If we have to ever fallback into default assumptions, it seems wiser 
to extend the physicall map to maximum_reservation, not current_reservation. 

-- 
Glauber de Oliveira Costa
Red Hat Inc.
"Free as in Freedom"

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