Re: [RFC PATCH V1 04/12] xen/arm: Introduce arch specific bits for IOREQ/DM features

[Oleksandr <olekstysh@xxxxxxxxx>]

On 05.08.20 19:41, Stefano Stabellini wrote:
Hi Stefano

> On Wed, 5 Aug 2020, Jan Beulich wrote:
> > On 05.08.2020 01:22, Stefano Stabellini wrote:
> > > On Mon, 3 Aug 2020, Oleksandr Tyshchenko wrote:
> > > > --- a/xen/include/asm-arm/p2m.h
> > > > +++ b/xen/include/asm-arm/p2m.h
> > > > @@ -385,10 +385,11 @@ static inline int set_foreign_p2m_entry(struct domain *d, 
> > > > unsigned long gfn,
> > > >                                           mfn_t mfn)
> > > >   {
> > > >       /*
> > > > -     * NOTE: If this is implemented then proper reference counting of
> > > > -     *       foreign entries will need to be implemented.
> > > > +     * XXX: handle properly reference. It looks like the page may not always
> > > > +     * belong to d.
> > > Just as a reference, and without taking away anything from the comment,
> > > I think that QEMU is doing its own internal reference counting for these
> > > mappings.
> > Which of course in no way replaces the need to do proper ref counting
> > in Xen. (Just FAOD, as I'm not sure why you've said what you've said.)
> Given the state of the series, which is a RFC, I only meant to say that
> the lack of refcounting shouldn't prevent things from working when using
> QEMU. In the sense that if somebody wants to give it a try for an early
> demo, they should be able to see it running without crashes.
Yes, for the early demo it works fine, however I don't use Qemu.


> Of course, refcounting needs to be implemented.
+


--
Regards,

Oleksandr Tyshchenko