Re: [Xen-devel] [PATCH] Disallow setting maxmem to higher value than total physical memory size

[Michal Novotny <minovotn@xxxxxxxxxx>]

On 09/01/2010 05:00 PM, Jan Beulich wrote:
> > > > On 01.09.10 at 16:50, Michal Novotny<minovotn@xxxxxxxxxx>  wrote:
> > > >          
> > On 09/01/2010 04:26 PM, Jan Beulich wrote:
> >      
> > > > > > On 01.09.10 at 16:18, Michal Novotny<minovotn@xxxxxxxxxx>   wrote:
> > > > > >
> > > > > >              
> > > > Oh, ok. It's not limited to dom0 nevertheless I don't see anything to be
> > > >
> > > >          
> > > And how does this play together with physical memory hotplug?
> > >
> > > Jan
> > >
> > >
> > >        
> > Well, it's reading the physical memory size using the xc.physinfo() call
> > so if this is handled correctly by hypervisor (since this  basically
> > issues a hypercall) then it should be working fine.
> >      
> Meaning the tools would auto-adjust maxmem_kb' for Dom0 when
> new memory got added? I can't see where that happens.
>
> Jan
>
>    
It's all based on xc.physinfo() call which is basically a hypercall. If 
there's a valid value coming from the hypervisor then it would be 
working fine.
You can see the call is there always on this line of my patch:

+ total_mem = int(xc.physinfo()['total_memory'])

If this is handled correctly by hypervisor then we're good in user-space 
as can be seen in tools/python/xen/lowlevel/xc/xc.c and 
tools/libxl/libxl.c where call to tools/libxc/xc_misc.c:xc_physinfo() 
resides.
Michal


--
Michal Novotny<minovotn@xxxxxxxxxx>, RHCE
Virtualization Team (xen userspace), Red Hat


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