[libvirt] [RFC PATCH v2 REBASE 00/18] Introduce vGPU mdev framework to libvirt

[Laine Stump]

On 03/17/2017 01:57 AM, Chen, Xiaoguang wrote:
> 
> 
>> -----Original Message-----
>> From: sendmail [mailto:justsendmailnothingelse at gmail.com] On Behalf Of Laine
>> Stump
>> Sent: Thursday, March 16, 2017 10:01 PM
>> To: libvir-list at redhat.com
>> Cc: Chen, Xiaoguang <xiaoguang.chen at intel.com>; Erik Skultety
>> <eskultet at redhat.com>; He, Yongli <yongli.he at intel.com>
>> Subject: Re: [libvirt] [RFC PATCH v2 REBASE 00/18] Introduce vGPU mdev
>> framework to libvirt
>>
>> On 03/16/2017 03:17 AM, Chen, Xiaoguang wrote:
>>> the screen call trace while start the VM (same for Ubuntu, Win10 etc)
>>> ======================================================
>>>
>>> ubuntu at z-nuc-11:~/vgpu-meta/libvirt-stage$ myvirsh start vgpu-ubuntu
>>> 2017-03-09 19:06:50.483+0000: 2232: info : libvirt version: 3.1.0
>>> 2017-03-09 19:06:50.483+0000: 2232: info : hostname: z-nuc-11.maas
>>> 2017-03-09 19:06:50.483+0000: 2232: warning : qemuDomainObjTaint:4056 :
>>> Domain id=1 name='vgpu-ubuntu'
>>> uuid=972b5e38-0437-11e7-8f97-d36dba74552d
>>> is tainted: high-privileges
>>
>> I haven't considered any of the rest of the log yet, but this caught my eye on a
>> first pass - "high-privileges" means that you're running qemu as root, so your test
>> is bypassing several issues that could cause vfio device assignment to fail on a
>> "standard" system.
> What do you mean for 'cause vfio device assignment to fail on a standard system'?

I mean that there are some device/file setup operations that libvirt
should be performing in order to make vfio device assignment work
properly in the case that the qemu process is unprivileged, and those
are often the source of bugs; if you run your tests with a privileged
qemu process, you're not testing any of the code that performs those
operations.

> 
>> It shouldn't be necessary to run qemu as root in order for
>> device assignment to work. Is there some specific reason that you're doing it this
>> way? (I'm guessing that you've set "user = root" in /etc/libvirt/qemu.conf)
> No. we will test the v3 using a non-root user.
>