Re: Shared memory and event channel

[Ritu kaur <ritu.kaur.us@gmail.com>]

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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@citrix.com>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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