Re: [Xen-devel] [PATCH RFC v2 2/2] linux/vnuma: Enables NUMA for domu PV guest

[Dario Faggioli <dario.faggioli@xxxxxxxxxx>]

On mar, 2013-09-17 at 15:17 +0100, David Vrabel wrote:
> On 17/09/13 09:34, Elena Ufimtseva wrote:
> > After the NUMA topology was received from Xen,
> > enable NUMA during boot. Should have CONFIG_NUMA
> > enabled in kernel.
> > 
> > Changes since v1:
> > - added additional checks for PV guest and hypercall
> > support before enablinf NUMA;
> 
> As I said in response to the other patch, I don't think this does the
> right thing.
> 
> I think xen_vnuma_support() needs to try the vnuma hypercall and check
> it is successful.
> 
That can surely be done, I think. Elena?

> > --- a/arch/x86/xen/setup.c
> > +++ b/arch/x86/xen/setup.c
> > @@ -20,6 +20,7 @@
> >  #include <asm/numa.h>
> >  #include <asm/xen/hypervisor.h>
> >  #include <asm/xen/hypercall.h>
> > +#include <asm/xen/vnuma.h>
> >  
> >  #include <xen/xen.h>
> >  #include <xen/page.h>
> > @@ -583,6 +584,9 @@ void __init xen_arch_setup(void)
> >     WARN_ON(xen_set_default_idle());
> >     fiddle_vdso();
> >  #ifdef CONFIG_NUMA
> > -   numa_off = 1;
> > +   if (!xen_initial_domain() && xen_vnuma_support())
> 
> I don't think there's a need to special case the initial domain here is
> there?
> 
This is actually something that Konrad asked, since, apparently, there
are AMD machines that just blows up, as Dom0, if this is on.

Therefore, since, right now, the status of Elena's work is "just DomUs",
we figured this could be fine for now.

Of course, the final goal (whether for Elena or for someone else to pick
it up) is to be able to enable vNUMA for Dom0 too, at which point we
definitely will have to figure out a way to kill this special casing
safely...

What do you think?

Regards,
Dario

-- 
<<This happens because I choose it to happen!>> (Raistlin Majere)
-----------------------------------------------------------------
Dario Faggioli, Ph.D, http://about.me/dario.faggioli
Senior Software Engineer, Citrix Systems R&D Ltd., Cambridge (UK)

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