Re: [PATCH] xen: arm: document which hypercalls (and subops) are supported on ARM

[Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>]

On Mon, Jul 29, 2013 at 03:56:51PM +0100, Ian Campbell wrote:
> On Tue, 2013-07-23 at 17:59 +0100, Ian Campbell wrote:
> > On Tue, 2013-07-23 at 16:34 +0100, Stefano Stabellini wrote:
> > > On Tue, 23 Jul 2013, Ian Campbell wrote:
> > > > On Tue, 2013-07-23 at 12:33 +0100, Stefano Stabellini wrote:
> > > > 
> > > > > You are missing all the common tmem ops.
> > > > 
> > > > tmem_ops are not hooked up in arm_hypercall_table, so they are currently
> > > > not supported. We should add them here when we add the necessary
> > > > support. ISTR stubbing out some functions which are used by tmem
> > > > (steal_page and donate_page perhaps?) so it's not just a case or wiring
> > > > it up either.
> > > 
> > > Right.. I was confused by the fact that we do compile tmem_op in Linux,
> > > even though XEN_TMEM is actually not available on ARM or ARM64
> > 
> > I started from the other end and looked at what the hypervisor actually
> > implements rather than what Linux calls. It's useful to validate from
> > both angles though. For now I think we should stick with documenting
> > what the hypervisor provides even if the kernel might try and
> > optimistically call other stuff too.
> 
> So did we decide whether to run with this patch or not?

I would say a better option is to just disable by default tmem in Xen hypervisor
for ARM. So even if you boot with 'tmem=1' nothing will happen.

That way when I get an ARM box up and I can test tmem we can just revert that
simple patch without much trouble.