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

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

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)

Ian.


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