Re: [Xen-ia64-devel] [PATCH][RFC][TAKE4] the P2M/VP patches

[Tristan Gingold <Tristan.Gingold@xxxxxxxx>]

Le Mercredi 12 Avril 2006 09:23, Tian, Kevin a écrit :
> From: Tristan Gingold [mailto:Tristan.Gingold@xxxxxxxx]
[...]
> >> >> >But this issues isn't specific to the P2M/VP patch.
> >> >
> >> >I don't agree with this solution.  I really prefer to have warnings
> >> > because it
> >> >means something got wrong.  domU shouldn't access to mmio.
> >> >
> >> >If you use a dummy page, a device driver may loop.
> >>
> >> Either way. Currently return 0 after warning actually same as dummy
> >> page.
> >
> >What about write accesses ?
> >
> >Tristan.
>
> First, current code is taking mfn 0 as the result when mapping is not
> found which is more problematic like write access as you mentioned
>
> Second, mapping to a dummy page has similar effect, but no harm
> for write
Writing page 0 is harmless!

> Last, the only way to prevent such io access is from guest itself,
> meant not compiling native drivers in. Or else there's no way for
> xen to handle it correctly.
User should disable drivers in domU.  Everybody agree with that!

You can also use command line options to do that.

But without warnings, you don't know there are drivers enabled.

Tristan.


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