Re: [Xen-devel] [PATCH V1 18/29] xen/arm: Don't map disabled device in DOM0

[Julien Grall <julien.grall@xxxxxxxxxx>]

On 09/09/2013 12:40 PM, Ian Campbell wrote:
> On Wed, 2013-08-28 at 15:47 +0100, Julien Grall wrote:
> > Linux should cope with 'status = "disabled"' in the Device Tree.
> This is devices which were disabled in the DT passed to Xen, rather than
> ones which we have disabled ourselves (e.g. the previous patch)?
Yes.


> > This solution can be used later to pass-through device to a specific guest.
> How? I thought disabled meant "not present/wired-up on this variant of
> the platform"? A user cannot be expected to edit the host DTB to enable
> passthrough. We might want a dtb_hide cmdline option, or to do it
> dynamically like pciback is capable of.
Disabled also means "the device is not presently operational, but it 
might become operational in the future".
> Or maybe I'm wrong above and this is indeed devices we have disabled
> ourselves?
I'm not sure it's usefull. But I don't see any reason to map disabled 
device in dom0.

> > Signed-off-by: Julien Grall <julien.grall@xxxxxxxxxx>
> >
> > ---
> >      Changes in v2:
> >          - Add a comment
> > ---
> >   xen/arch/arm/domain_build.c |    6 +++++-
> >   1 file changed, 5 insertions(+), 1 deletion(-)
> >
> > diff --git a/xen/arch/arm/domain_build.c b/xen/arch/arm/domain_build.c
> > index d56bc70a..11f247b 100644
> > --- a/xen/arch/arm/domain_build.c
> > +++ b/xen/arch/arm/domain_build.c
> > @@ -416,9 +416,13 @@ static int handle_node(struct domain *d, struct 
> > kernel_info *kinfo,
> >        *  - Device used by Xen: Obviously dom0 can't use them
> >        *  - Memory: the guest will see a different view of memory. It will
> >        *  be allocated later.
> > +     *  - Disabled device: Linux is able to cope with status="disabled"
> > +     *  property. Therefore these device doesn't need to be mapped. This
> > +     *  solution can be use later for pass through.
> >        */
> >       if ( dt_device_used_by(np) != DOMID_XEN &&
> > -         !dt_device_type_is_equal(np, "memory") )
> > +         !dt_device_type_is_equal(np, "memory") &&
> > +         dt_device_is_available(np) )
> >       {
> >           res = map_device(d, np);

--
Julien Grall

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