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xen-devel
Re: [Xen-devel] questions about xen device pass-through.
On Tue, Aug 23, 2011 at 06:02:49PM -0400, Dushmanta Mohapatra wrote:
> Thanks Jean.I got it resolved.
>
> But now I am facing an issue at the next step. After I assign the device
> back to Dom0,
> there is an issue in DomU reverting back to the virtual mode.
>
> Initially I start an Windows 7 HVM DomU and give it virtualized access to
> various devices.
> After that I unbind some devices (Ethernet in this case), assign them to
> pciback and attach them to DomU (using xm pci-attach). At this stage DomU
> recognizes the hotplugging and I get passthrough IO. Afterwards I detach
> the device from DomU (using xm pci-detach). At this stage the device gets
> assigned to pciback. So I unbind it from pciback and bind the device back
> to Dom0 using sysfs mechanisms. So Dom0 gets direct access to the device.
> Dom0 network works fine after this.
>
> But after this DomU does not revert back to the virtual interface it was
> using earlier. In case of ethernet, I can still see a vif1.0 interface if
> I do a ifconfig in Dom0. But there is no network access in DomU. I tried
> to reconfigure the network/connection etc. inside Windows7 DomU, but could
> not get it working.
>
> Please tell me I am missing some thing or should be doing it some other
> way.
> Let me know if I need to give some more information.
>
Did you check if the vif is still attached to the bridge?
(brctl show)
And I guess this was a different NIC than what's used in the bridge?
-- Pasi
> (I am just testing for ethernet right now..I am planning to try this for
> other kinds of devices also like VGA,USB, Wireless etc.)
>
> Thanks,
> Dushmanta
>
> On Wed, Aug 17, 2011 at 6:27 PM, Jean Guyader <[1]jean.guyader@xxxxxxxxx>
> wrote:
>
> On 17 August 2011 20:55, Dushmanta Mohapatra
> <[2]dushmanta.mohapatra@xxxxxxxxx> wrote:
> > Hello,
> >
> > I have some doubts/questions regarding device passthrough support in
> Xen.
> > I will really appreciate some help/suggestions.
> >
> > (I am using a Intel Core i5 vPro based Lenovo thinkpad T520 (Intel
> graphics
> > adapter).
> > I am running Xen 4.1.1 and PVOPS based Linux 2.6.32.41 kernel as Dom0.
> I use
> > Windows XP
> > and Windows 7 as my HVM Domus. lspci details are attached.)
> >
> > I am trying to achieve the following: Initially allow
> > direct access to the primary devices (graphics/ethernet/wireless/USB)
> to an
> > HVM DomU. After wards,
> > depending on the need I want to re-assign the direct access of these
> devices
> > back to Dom0 and
> > have the DomU access the devices in a virtual manner.
> >
> > So my question is: Is it possible to do it? Is it possible for VGA/
> > graphics?
> >
> > I have tried a few things and following is what I am being able to do:
> >
> > I am being able to provide direct access to devices
> > (wireless/ethernet/graphics etc) to HVM DomUs.
> > And also I am being able to dynamically change the direct access to
> these
> > devices between
> > the various HVM DomUs (tested with WinXP and Windows 7) in case of
> > ethernet/USB etc. I am being
> > able to detach it from one DomU and attach it to another. (This is not
> > working with VGA direct access
> > though.)
> >
> > But I am not being able to reattach these devices back to Dom0. I have
> tried
> > the sysfs way and initial
> > boot time passthrough.
> >
> > I have also tried the stubdomain way, but when I do not hide the
> devices
> > from Dom0 (at boot time) and later try to assign them to stubdomain,
> my Dom0
> > gets rebooted automatically. I am following
> > the steps mentioned in:
> > [3]http://mirror.choon.net/xen/xen-unstable.hg/docs/misc/vtd.txt
> >
> > So could some one tell me if these behaviors are expected or
> > if I might be doing something wrong.
> >
> > I will really appreciate any help. Please let me know if more
> information is
> > needed from my side.
> >
>
> Hi,
>
> If you detach a pass through device from a domU it gets reassigned to
> dom0 automatically.
> The problem you are having is that pciback in dom0 still own the
> device that why it looks like
> the device isn't working in dom0.
>
> You'll have to manually unbind the device from picback and bind it to
> another driver in dom0.
> That can be done through the sysfs driver nodes "bind" and "unbind".
> Jean
>
> References
>
> Visible links
> 1. mailto:jean.guyader@xxxxxxxxx
> 2. mailto:dushmanta.mohapatra@xxxxxxxxx
> 3. http://mirror.choon.net/xen/xen-unstable.hg/docs/misc/vtd.txt
> _______________________________________________
> Xen-devel mailing list
> Xen-devel@xxxxxxxxxxxxxxxxxxx
> http://lists.xensource.com/xen-devel
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