[libvirt] [PATCH v4 00/14] Introduce vGPU mdev framework to libvirt

[yonglihe]

> On 03/28/2017 10:05 PM, yonglihe wrote:
>> On 2017年03月27日 15:42, yonglihe wrote:
>>> Verify Summary:
>>> * the none rooted mode starting a high-privileges VM actually.
>>>
>>> The configurations is source generated default value except tls disabled.
>>>
>>>
>>> 1. rooted
>>>
>>> virsh define ./libvirt/vgpu-win10.xml
>>> Domain vgpu-win10 defined from ./libvirt/vgpu-win10.xml
>>>
>>> ubuntu at z-nuc-11:~/vgpu-meta/libvirt-stage$ virsh start vgpu-win10
>>> 2017-03-26 23:28:57.385+0000: 2886: info : libvirt version: 3.2.0
>>> 2017-03-26 23:28:57.385+0000: 2886: info : hostname: z-nuc-11.maas
>>> 2017-03-26 23:28:57.385+0000: 2886: warning : qemuDomainObjTaint:4155
>>> : Domain id=1 name='vgpu-win10'
>>> uuid=916c5c36-0437-11e7-a23d-830ed1295d00 is tainted: high-privileges
>>> 2017-03-26 23:28:58.010+0000: 2886: warning :
>>> virDomainAuditHostdev:456 : Unexpected hostdev type while encoding
>>> audit message: 4
>>> Domain vgpu-win10 started
>>>
>>>
>>> 2. None rooted
>>> virsh -c qemu:///session
>>> Welcome to lt-virsh, the virtualization interactive terminal.
>
> The above line makes me think that you're mixing up "unprivileged
> libvirtd" with "unprivileged qemu".
>
> When you connect to virsh with "virsh -c qemu:///session" you are using
> an unprivileged copy of libvirtd started for your specific uid, and that
> libvirtd will:
>
> 1) not do any of the uid/permission/selinux/apparmor changes to the
> files/devices that will be used by the qemu process. (because it can't)
>
> 2) try to modify the locked memory limit for the qemu process, but
> likely fail because it needs more than the user's default limit. (I see
> below that you ran into this).
>
> 3) run qemu as the same unprivileged user.
>
>
> When you connect to virsh with the default URL (qemu:///system) you will
> connect to the system instance of libvirtd, which is running as root. It
> will:
>
> 1) modify uid/permissions/selinux/apparmor settings of any files/devices
> according to the "user" setting in /etc/libvirt/qemu.conf.
>
> and after forking the qemu process:
>
> 2) modify the locked memory limit to accommodate the needs of any
> assigned devices and
>
> 3) change the uid of the qemu process to the "user" setting from
> qemu.conf and drop all privileges
>
> (in the case that the "user" in qemu.conf is set to root, then step 3
> doesn't happen).
>
> It sounds like you are using an "unprivileged libvirtd" in your tests,
> which will create the need to chown the various device files and
> manually change the ulimit for the login session that is running "virsh
> -c qemu:///session" (and thus starting up the unprivileged libvirtd
> which gets started on demand).
>
> The more common scenario is to use virsh -c qemu:///system (or simply
> run virsh as root and not add the URL so that the default is used), and
> to leave the qemu user set to "qemu" (or in some distros I think it is
> set to "kvm" by default).
thanks explain all of these,  this is so big help to better 
understanding the processes of libvirt and what problem i'm encounter,
thanks, very much!

Regards
Yongli He
>
>>> virsh # define ./libvirt/vgpu-win10.xml
>>> Domain vgpu-win10 defined from ./libvirt/vgpu-win10.xml
>>>
>>> virsh # start vgpu-win10
>>> 2017-03-26 23:38:11.220+0000: 2882: warning : qemuDomainObjTaint:4155
>>> : Domain id=4 name='vgpu-win10'
>>> uuid=916c5c36-0437-11e7-a23d-830ed1295d00 is tainted: high-privileges
>>> 2017-03-26 23:38:12.356+0000: 2882: warning :
>>> virDomainAuditHostdev:456 : Unexpected hostdev type while encoding
>>> audit message: 4
>>> Domain vgpu-win10 started
>> Please ignore above none rooted testing result, my fault. the proper
>> test given following result:
>>
>> to successfully starting a non rooted vm, the following operation needed:
>> 1.change the ownership/access right of the mdev corresponding vfio
>>     sudo chown ubuntu:ubuntu /dev/vfio/0
>>
>> 2. set a correct ulimit -l  for the vm
>> sudo sh -c "ulimit -l 3074424832 && exec su $LOGNAME"
>>
>> otherwise, it running into the following error:
>> virsh # start vgpu-win10
>>   internal error: Process exited prior to exec: libvirt:  error : cannot
>> limit locked memory to 3074424832: Operation not permitted
> This is to be expected - both of these extra steps are also needed if
> you try to assign a standard PCI device using VFIO using unprivileged
> libvirtd. This is the best that can be expected without any component
> having root privileges.
>
> If you run the same test using qemu:///system, both of these should be
> taken care of automatically.
>
>> my testing bed is Ubuntu 14.04, there is a similar bug ever reported:
>> https://bugs.launchpad.net/ubuntu/+source/libvirt/+bug/1276719
> The original report (filed 2.5 years ago, and resolved soon after) was
> due to apparmor not doing the right stuff to the necessary files in
> sysfs. Many later comments and error messages were from people who were
> using the tools incorrectly (e.g. using <qemu:commandline> to manually
> add "-device vfio-pci" args to the qemu process, making it impossible
> for libvirt to recognize that it must perform steps 2 & 3 listed above.
>
>> I could not make sure if there is special requirements  run virsh
>> directly from the source tree using the ./run scripts. fix me.
> I'm fairly certain the reason you're needing to perform those two extra
> steps are because you're using qemu:///session instead of qemu:///system.
>
>
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