Re: [Xen-devel] error when pass through device to guest with qemu-xen-dir-remote

["Zhang, Yang Z" <yang.z.zhang@xxxxxxxxx>]

> -----Original Message----- From: xen-devel-bounces@xxxxxxxxxxxxx
> [mailto:xen-devel-bounces@xxxxxxxxxxxxx] On Behalf Of Zhou, Chao Sent:
> Thursday, August 09, 2012 2:49 PM To: Ian Campbell; Stefano Stabellini
> Cc: Zhang, Yang Z; Anthony Perard; xen-devel Subject: Re: [Xen-devel]
> error when pass through device to guest with qemu-xen-dir-remote
> 
> I rebuild the upstream QEMU according to the wiki, but device static 
> assignment
> doesn't work, no lspci output in guest. However hotplug & unplug works fine.
> 
> -----Original Message----- From: xen-devel-bounces@xxxxxxxxxxxxx
> [mailto:xen-devel-bounces@xxxxxxxxxxxxx] On Behalf Of Ian Campbell Sent:
> Friday, August 03, 2012 6:36 PM To: Stefano Stabellini Cc: Zhang, Yang
> Z; Anthony Perard; xen-devel Subject: Re: [Xen-devel] error when pass
> through device to guest with qemu-xen-dir-remote
> 
> On Fri, 2012-08-03 at 11:29 +0100, Stefano Stabellini wrote:
>> On Fri, 3 Aug 2012, Zhang, Yang Z wrote:
>>> When create guest with device assigned, it shows the error and the
>>> device wasn't able to work inside guest: libxl: error:
>>> libxl_qmp.c:288:qmp_handle_error_response: received an error message
>>> from QMP server: Parameter 'driver' expects a driver name
>>> 
>>> It only fails with qemu-xen-dir-remote(Is this tree more close to
>>> upstream qemu?). I don't see the error with the traditional Qemu. I
>>> also tried qemu-upstream, but it fails when I try to enable pci
>>> pass-through
> for xen. I think Anthony's patch to add pci pass-through support for Xen is
> accepted by qemu-upstream, am I right?
>> 
>> Yes, it was accepted, but it is present only in upstream QEMU (from
>> git://git.qemu.org/qemu.git), not the tree we are currently using in
>> xen-unstable for development
>> (git://xenbits.xensource.com/qemu-upstream-unstable.git).
>> Make sure you are using the right tree!
> 
> http://wiki.xen.org/wiki/QEMU_Upstream has some notes on how to use the
> upstream qemu tree instead of our stable branch of upstream.
> 
>> 
>> Anthony is currently on vacation and is going to be back in about a
>> week.
>> 
>>> Another question:
>>> Now I am trying to add some features (relevant to pass through device) to
> Qemu, which tree should I use? Since traditional qemu is great different from
> qemu-upstream, it is too old to develop patch base on it. But besides the old 
> one,
> I cannot find a working qemu.
>> 
>> You should use upstream QEMU, I am going to rebase our tree on that
>> early on in the 4.3 release cycle.

Hi Anthony

I found the issue is caused by PV driver. Since RHEL6 integrated PV driver by 
default, when booting rhel6 as guest, it will load the PV driver and write the 
xen platform device to notify qemu to unplug all NICs including the pass 
through device. This definitely is wrong. We only need to unplug the emulator 
device, and leave pass through device.

Best regards,
Yang



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