Re: [Xen-devel] [PATCH] libxl: Don't insert PCI device into xenstore for HVM guests

[Ross Lagerwall <ross.lagerwall@xxxxxxxxxx>]

On 05/29/2015 10:50 AM, Wei Liu wrote:
> On Fri, May 29, 2015 at 10:43:08AM +0100, Ross Lagerwall wrote:
> > On 05/29/2015 10:41 AM, Wei Liu wrote:
> > > On Fri, May 29, 2015 at 08:59:45AM +0100, Ross Lagerwall wrote:
> > > > When doing passthrough of a PCI device for an HVM guest, don't insert
> > > > the device into xenstore, otherwise pciback attempts to use it which
> > > > conflicts with QEMU.
> > > >
> > > > This manifests itself such that the first time a device is passed to a
> > > > domain, it succeeds. Subsequent attempts fail unless the device is
> > > > unbound from pciback or the machine rebooted.
> > > The commit message looks sensible to me. However this might break
> > > qemu-trad PCI passthrough if I'm not mistaken. What QEMU version are you
> > > using?  Upstream or trad? Have you tested both of them?
> > qemu-trad. I haven't tested with qemu-upstream.
> I don't quite get this. Doesn't qemu-trad depends on those xenstore
> nodes for PCI passthrough information?  What did I miss?
A different set of xenstore keys are used for communication between 
libxl and QEMU. The communication between libxl and QEMU happens further 
up in the same function:
http://xenbits.xen.org/gitweb/?p=xen.git;a=blob;f=tools/libxl/libxl_pci.c;h=e0743f8112689b340ba7de88bc8895b62105aaba;hb=HEAD#l901

Regards,
--
Ross Lagerwall

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