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

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

On Mon, 2013-07-29 at 14:09 -0400, Konrad Rzeszutek Wilk wrote:
> 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.

The "this patch" I was talking about was the original documentation only
patch at the root of this thread which has nothing to do with tmem.

What we want to do with tmem on ARM is a different question. If you want
to start a separate thread on that topic please feel free.

Ian.


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