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Re: [Xen-devel] Q on ioctl support in netfront/netback

To: Daniel Stodden <daniel.stodden@xxxxxxxxxx>
Subject: Re: [Xen-devel] Q on ioctl support in netfront/netback
From: ravi kerur <rkerur@xxxxxxxxx>
Date: Wed, 17 Feb 2010 07:44:02 -0800
Cc: Paul Durrant <Paul.Durrant@xxxxxxxxxx>, "xen-devel@xxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxx>
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Hi Daniel,

These registers are(DMA, statistics, and other h/w related to NIC), I just want to read those registers and in very few cases write to them. Currently, I can run those applications in dom0 and access directly but I wanted to check if anything is possible from domU? Other thing I tried using sockets from domU to dom0(albeit I had clear firewall settings in dom0) but Citrix support forum mentioned it is not the recommended way. I am not sure whether I answered your question, let me know if you need additional info.

Thanks
-RK

On Tue, Feb 16, 2010 at 7:26 PM, Daniel Stodden <daniel.stodden@xxxxxxxxxx> wrote:
On Mon, 2010-02-15 at 10:54 -0500, ravi kerur wrote:
> Paul,
>
> Registers are not in netback, they are h/w registers on NIC and the
> driver supports reads/writes via ioctl calls. Driver is in dom0 and
> application which reads/writes registers is run in domU.

Why do you want to map or preserve some register interface?

Is this some sort of hardware multiplex? As Konrad pointed out, in that
case a PV driver is probably the wrong approach altogether.

If what you want is just a bunch of extended control plane attributes,
rather consider mapping them to xenstore.

That's slightly more asynchronous and probably not a great option if you
need a synchronous interface. Especially if you need individual return
values, not just a bunch of fields to write into.

If the latter case, next option would be some dedicated shared memory
structure. But it's hard to imagine something like that to make
sense. :}

Daniel


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