Re: [Xen-devel] [PATCH 06/14 v4] xen/arm: vpl011: Add a new domctl API to initialize vpl011

[Julien Grall <julien.grall@xxxxxxx>]

On 06/14/2017 10:16 AM, Bhupinder Thakur wrote:
> Hi Julien,
Hi Bhupinder,

> > > diff --git a/tools/libxc/include/xenctrl.h b/tools/libxc/include/xenctrl.h
> > > index 1629f41..77425dd 100644
> > > --- a/tools/libxc/include/xenctrl.h
> > > +++ b/tools/libxc/include/xenctrl.h
> > > @@ -884,6 +884,23 @@ int xc_vcpu_getcontext(xc_interface *xch,
> > >                          uint32_t domid,
> > >                          uint32_t vcpu,
> > >                          vcpu_guest_context_any_t *ctxt);
> >
> > Newline here please.
> ok.
> > [...]
> >
> > > diff --git a/tools/libxl/libxl_arch.h b/tools/libxl/libxl_arch.h
> > > index 5e1fc60..d1ca9c6 100644
> > > --- a/tools/libxl/libxl_arch.h
> > > +++ b/tools/libxl/libxl_arch.h
> > > @@ -32,6 +32,13 @@ _hidden
> > >   int libxl__arch_domain_create(libxl__gc *gc, libxl_domain_config
> > > *d_config,
> > >                  uint32_t domid);
> > >
> > > +/* arch specific internal domain creation finish function */
> > > +_hidden
> > > +int libxl__arch_domain_create_finish(libxl__gc *gc,
> > > +                                     libxl_domain_build_info *info,
> > > +                                     uint32_t domid,
> > > +                                     libxl__domain_build_state *state);
> >
> > Can you explain why you need a new arch helper rather than using the current
> > one?
> libxl__arch_domain_create() is called from libxl__build_pre(). This
> function is called before libxl__build_pv(). By this time the domain
> has not be created and I found that if I tried to initialize vpl011
> from inside libxl__arch_domain_create() then initialization was
> failing due to prepare_ring_for_helper() failing.
What do you mean by the domain has not been created? The domain has 
already been created (you have a domid in hand) when you 
libxl__build_pre. So the problem is different.
Looking at the code, I guess the problem is because the vuart pfn will 
be allocated by xc_dom_build_image called by libxl_build_pv -> 
libxl__build_dom.
> So I had to create another function which will be called from
> libxl__build_post() after domain has been setup.
It looks a bit odd to me to create the vpl011 UART that late in the 
process because when you read the code you would expect all the hardware 
to be setup after libxl__arch_domain_finalise_hw_descriptions is called.
But I understand it is not possible to do it as the ring has not yet 
been allocated. So is there a way to allocate the ring before?
Wei, Ian, do you have any opinions on what should the workflow in libxl?

Cheers,

--
Julien Grall

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