Re: [Xen-devel] frontend and backend devices and different types of hw - pci for example

[Mark Williamson <mark.williamson@xxxxxxxxxxxx>]

> Do you think that an emulated PCI layer underneath every domU could be a
> possibility for a solution of moving PCI devices to user domains? I have
> had some success with it and got as far as for example moving a PCI
> ethernet card or the whole USB controller to a user domain and making the
> user domain kernel activate its drivers.

Possibly...  I would have been inclined to do it using some sort of 
interdomain communication rather than using an emulator in Xen but I'm 
actually open to persuasion that I'm wrong on this point ;-)

> I did this by reading the PCI 
> config space (256 bytes) from the device and presenting the data to the
> user level in the emulated PCI bus. However I have then encountered a
> couple of problems afterwards when trying to activate the IRQ. There seems
> to be some translation going on of a PCI IRQ number to the actual number
> the system is using (due to APIC I suppose) and so the data exchange with
> the device did not start.

Thanks for the extra detail.

Hmmm.  Sounds a bit weird...  Afraid I'm not sure what might be going on here.

Cheers,
Mark

>   Stefan
>
> > > >Note that giving direct physical access to a PCI device has security
> > > >implications since the guest can potentially use the cards' DMA
> > > > capabilities to access all of physical memory.
> > >
> > > Will IOMMU support help solving this security problems ?
> >
> > Yes but only if it enforces access permissions fully i.e. I don't think
>
> the
>
> > IOEMU in AMD64 machines is sufficient.  From the looks of Pacifica it
>
> might
>
> > have sufficient support to control the DMA problem, I'm sure Intel have
>
> a
>
> > similar solution (although I don't think it's implemented in Vanderpool
>
> -
>
> > they'll probably need chipset support).
> >
> > Cheers,
> > Mark
> >
> > > Regards,
> > > Sting
> > >
> > > On 8/28/05, Mark Williamson <mark.williamson@xxxxxxxxxxxx> wrote:
> > > > > What about other devices ? let's say a PCI sound card (or any
>
> other PCI
>
> > > > > device). Where is the software that should handle it ? I remember
>
> I saw
>
> > > > > somewhere some discussion about PCI configuration space, but I
>
> don't
>
> > > > > remember where.
> > > >
> > > > That code is in Xen itself in Xen 2.0.  Xen controls access to the
>
> PCI
>
> > > > configuration spaces so that guests can only see the devices they
>
> have
>
> > > > access to.  It also controls the IO memory / ports that domains are
> > > > allowed to access in order to control PCI devices.
> > > >
> > > > Note that giving direct physical access to a PCI device has security
> > > > implications since the guest can potentially use the cards' DMA
> > > > capabilities to access all of physical memory.  The front/back-style
> > > > devices do not have this limitation.
> > > >
> > > > Btw, I've laid some groundwork for a virtual sound device but
>
> haven't had
>
> > > > much time to hack on it yet.
> > > >
> > > > Cheers,
> > > > Mark
> >
> > _______________________________________________
> > Xen-devel mailing list
> > Xen-devel@xxxxxxxxxxxxxxxxxxx
> > http://lists.xensource.com/xen-devel

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