Re: [Xen-users] Xen support for AMD's IOMMU

[Mark Williamson <mark.williamson@xxxxxxxxxxxx>]

> > There's some sort of memory permissions table for PCI devices
> > though, isn't
> > there?  I vaguely remember it being in the arch manual, but I haven't
> > actually known any software use it (at least in the context of Xen!)
>
> Yes, that's called "DEV" or "Device Exclusion Vector", and I'm also
> unaware of any software that is commonly available that uses this. It
> doesn't actually solve the most commonly requested feature in IOMMU,
> which is the ability to run a HVM-guest using a PCI-device,

True.

> and I wasn't 
> really considering the "security aspect" of IOMMU when I wrote my answer
> [and the DEV feature is definitely not usable to solve the PCI-device in
> HVM problem].

And I wasn't really considering the HVM aspect when I wrote my question :-)  
Good point!

Still, it'd be nice to support the DEV at some stage for purposes of reducing 
the trust level of PV domains with device access (i.e. there's much less 
point putting a driver into an isolated domain if it can DMA everywhere 
anyhow!)...  if it can be supported with sufficiently good performance, this 
would be kinda cool.

Cheers,
Mark

> --
> Mats
>
> > Cheers,
> > Mark
> >
> > > As to a direct answer to the question: There is no AMD
> >
> > IOMMU software in
> >
> > > 3.0.{2,3,4}. There's been a patch supplied by Mark
> >
> > Langsdorf to use the
> >
> > > GART in the current AMD64 architecture for IOMMU operations
> >
> > (same way as
> >
> > > the Linux kernel itself uses this portion of the chip).
> >
> > This is NOT to
> >
> > > be confused with the REAL IOMMU design.
> > >
> > > --
> > > Mats
> > >
> > > > Thanks
> > > > Daniel
> > > >
> > > > _______________________________________________
> > > > Xen-users mailing list
> > > > Xen-users@xxxxxxxxxxxxxxxxxxx
> > > > http://lists.xensource.com/xen-users
> > >
> > > _______________________________________________
> > > Xen-users mailing list
> > > Xen-users@xxxxxxxxxxxxxxxxxxx
> > > http://lists.xensource.com/xen-users
> >
> > --
> > Dave: Just a question. What use is a unicyle with no seat?
> > And no pedals!
> > Mark: To answer a question with a question: What use is a skateboard?
> > Dave: Skateboards have wheels.
> > Mark: My wheel has a wheel!

-- 
Dave: Just a question. What use is a unicyle with no seat?  And no pedals!
Mark: To answer a question with a question: What use is a skateboard?
Dave: Skateboards have wheels.
Mark: My wheel has a wheel!

_______________________________________________
Xen-users mailing list
Xen-users@xxxxxxxxxxxxxxxxxxx
http://lists.xensource.com/xen-users