Re: [Xen-ia64-devel] iosapic virtualisation

[Tristan Gingold <Tristan.Gingold@xxxxxxxx>]

Le Mercredi 01 Février 2006 16:48, Alex Williamson a écrit :
> On Wed, 2006-02-01 at 10:11 +0100, Tristan Gingold wrote:
> > Le Mardi 31 Janvier 2006 20:53, Alex Williamson a écrit :
[...]
> > >       * We need to paravirtualize reads of the IOSAPIC as well as
> > >         writes.  Since the IOSAPICs use a windowing register scheme, a
> > >         domain reading an IOSAPIC could interfere with Xen writing or
> > >         cause races with other domains.  This will also enable us to
> > >         hide the physical IOSAPIC structure if we need to at some
> > > point.
> >
> > Ok.  I think this point is rather moot because linux doesn't read IOSAPIC
> > (except version, which is not windowed).  However for completion I will
> > do it.
>
>   Doesn't iosapic_version() call iosapic_read() which writes to the
> IOSAPIC_REG_SELECT register?  I was concerned that's where we'd run into
> a problem, but maybe I'm forgetting something about how IOSAPICs work.
No, you are right, version *is* windowed.
I have modifications here: it now read through an hypercall.

> By the way, I don't see iosapic.h in the patch set, probably why it
> didn't compile for me.  Thanks,
Sorry, I indeed forgot it.  You can grab the one from linux.

Thank you for all your comments,
Tristan.


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