From mboxrd@z Thu Jan  1 00:00:00 1970
From: Gerd Hoffmann <kraxel@redhat.com>
Subject: Re: [Qemu-devel] [RFC PATCH v1 1/1] vGPU core driver : to provide
 common interface for vGPU.
Date: Wed, 17 Feb 2016 14:08:18 +0100
Message-ID: <1455714498.9127.28.camel@redhat.com>
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Cc: "Tian, Kevin" <kevin.tian@intel.com>,
	"Ruan, Shuai" <shuai.ruan@intel.com>,
	"Song, Jike" <jike.song@intel.com>,
	"kvm@vger.kernel.org" <kvm@vger.kernel.org>,
	Kirti Wankhede <kwankhede@nvidia.com>,
	qemu-devel <qemu-devel@nongnu.org>,
	Alex Williamson <alex.williamson@redhat.com>,
	Paolo Bonzini <pbonzini@redhat.com>,
	"Lv, Zhiyuan" <zhiyuan.lv@intel.com>
To: Neo Jia <cjia@nvidia.com>
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  Hi,

> For example, how to locate the path of a given VM?

You go ask libvirt, the domain xml will have the info.

> Whoever is going to configure
> the qemu has to walk through *all* the current vgpu path to locate the UUID to
> match the QEMU's VM UUID.

No.  qemu simply uses the path it get passed from libvirt.  libvirt
simply uses whatever is stored in the domain xml.

i.e. you'll have a config like this:

<domain type='kvm'> 
  <name>rhel7-vfio</name>
  <uuid>0990b05d-4fbd-49bf-88e4-e87974c64fba</uuid>
  [ ... ]
  <devices>
    [ ... ]
    <hostdev mode='subsystem' type='pci' managed='yes'>
      <source>
        <address sysfs='/sys/devices/virtual/vgpu/${name}'/>
      </source>
      <address type='pci' domain='0x0000'
               bus='0x00' slot='0x04' function='0x0'/>
    </hostdev>

> I think I has answered this, UUID is not a user space or kernel space
> concept, it is just a generic way to represent object,

Yes.  But the above sounds like you want to use UUIDs to *link* two
objects, by assigning the same uuid to both vm and vgpu.  This is *not*
how uuids should be used.  Each object should have its own uuid.

You can use uuids to name the vgpus if you want of course.  But the vgpu
uuid will will have no relationship whatsoever to the vm uuid then.

cheers,
  Gerd