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Re: [Xen-devel] Is there a way to map pv guest pseudo physical address i

At 17:26 +0800 on 27 Jun (1309195596), Wei Liu wrote:
> > You need to arrange for the Xen specific bit of the virtio frontend to
> > do the p2m translation. All externally visible addresses from a PV guest
> > must be in MFN space.
> >
> That's not a good approach. Dirvers reside on a higher level from the
> "Xen specific bit". Doing this kind of translation will break their
> generality. But there seems no other way to get this job done...

This is a general problem with operating systems: bus addresses are not
always the same as CPU memory addresses (even though in the easy case of
a simple x86 PC they often are).  This is why OSes already have
interfaces to allocate DMA-able memory and to translate between the
address that CPU will map and the one the peripheral should use.  If
your driver's not using the right address-space to program its hardware
it is broken; the Xen PV model is just an extreme case of this.


Tim Deegan <Tim.Deegan@xxxxxxxxxx>
Principal Software Engineer, Xen Platform Team
Citrix Systems UK Ltd.  (Company #02937203, SL9 0BG)

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