Re: [Xen-devel] Shared memory and event channel

[Ritu kaur <ritu.kaur.us@xxxxxxxxx>]

Hi Ian,

Thanks for your inputs, I skimmed through Intel 82576 SR-IOV document
and it looks like it needs hardware support and I don't think our
hardware has it(will double check with our team). I believe currently there is no good solution other than using pci passthrough(with a single domU access). I just want to bring one thing and I hope it was not missed out from my earlier email i.e 

"The NIC registers are memory mapped, can I
take "machine memory address space(which is in dom0)" and remap it to
domU's such that I can get multiple domU access. "

The above soln is just a thought, not sure it's feasible.

Thanks

On Tue, Feb 23, 2010 at 7:42 AM, Ian Campbell <Ian.Campbell@xxxxxxxxxx> wrote:

On Tue, 2010-02-23 at 14:47 +0000, Konrad Rzeszutek Wilk wrote:
> On Tue, Feb 23, 2010 at 09:38:26AM +0000, Ian Campbell wrote:
> > On Mon, 2010-02-22 at 22:16 +0000, Ritu kaur wrote:
> > >
> > > All I need to  is access NIC registers via domU's(network controller
> > > will still be working normally). Using PCI passthrough solves the
> > > problem for a domU, however, it doesn't solve when multiple domU's
> > > wanting to read NIC registers(ex. statistics).
> >
> > Direct access to hardware registers and availability of the device to
> > multiple guest domains are mutually exclusive configurations under Xen
> > (in the absence of additional technologies such as SR-IOV).
> >
> > The paravirtual front and back devices contain no hardware specific
> > functionality, in this configuration all hardware specific knowledge is
> > contained in the driver in domain 0. Guests use regular L2 or L3
> > mechanisms such as bridging, NAT or routing to obtain a path to the
> > physical hardware but they are never aware of that physical hardware.
> >
> > PCI passthrough allows a guest direct access to a PCI device but this is
> > obviously incompatible with access from multiple guests (again, unless
> > you have SR-IOV or something similar)
>
> What if the netback was set be able to work in guest mode? This way you
> could export it out to the guests?

Like a driver domain model? That would work (I think) but is still not
the same as having multiple domain's with access to the physical
registers. netback in a guest works in exactly the same as how it works
for domain 0.

Ian.

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