[libvirt-users] [virtual interface] detach interface during boot succeed with no changes

[Yalan Zhang]

Hi Laine,

As for the hot-unplug behavior, I have one more question about it, could
you please help to confirm?

unplugging a PCI device properly requires cooperation from the guest OS.
> If the guest OS isn't running yet, the unplug won't complete, so qemu
> (and libvirt) still show the device as plugged into the guest.
>
> virsh reports success on the unplug because unplugging a device is done
> asynchronously - the "success" means "libvirt successfully told qemu to
> unplug the device, qemu has told the virtual machine to unplug the
> device, and is waiting for acknowledgment from the virtual machine that
> the guest has completed removal". At some later time the guest OS may
> complete its part of the unplug; when that happens, qemu will get a
> notification and will send an event to libvirt - at that time the device
> will be removed from libvirt's list of devices.
>
> tl;dr - this is all expected.
>

The question is that, when I unplug it during boot, the virsh cmd will
succeed but the interface still exists, which is expected.
After the vm boot successfully, the guest OS will *not* complete this
removal. When I tried to detach it again, it reported that the device was
in the process of unplugging.
Is this acceptable?

# virsh detach-interface rhel_new network 52:54:00:36:a8:d4
Interface detached successfully
# virsh domiflist rhel_new
 Interface   Type      Source    Model    MAC
-------------------------------------------------------------
 vnet4       network   default   virtio   52:54:00:36:a8:d4

# virsh detach-interface rhel_new network 52:54:00:36:a8:d4
error: Failed to detach interface
error: internal error: unable to execute QEMU command 'device_del': Device
net0 is already in the process of unplug

Thank you!

Yalan


On Thu, Sep 14, 2017 at 12:48 AM Laine Stump <laine at laine.org> wrote:

> On 09/04/2017 03:37 AM, Yalan Zhang wrote:
> > Hi guys,
> >
> > when I detach an interface from vm during boot (vm boot not finished), it
> > always fail. I'm not sure if there is an existing bug. I have
> > confirmed with someone that for disk, there is similar behavior, if
> > this is also acceptable?
>
> unplugging a PCI device properly requires cooperation from the guest OS.
> If the guest OS isn't running yet, the unplug won't complete, so qemu
> (and libvirt) still show the device as plugged into the guest.
>
> virsh reports success on the unplug because unplugging a device is done
> asynchronously - the "success" means "libvirt successfully told qemu to
> unplug the device, qemu has told the virtual machine to unplug the
> device, and is waiting for acknowledgment from the virtual machine that
> the guest has completed removal". At some later time the guest OS may
> complete its part of the unplug; when that happens, qemu will get a
> notification and will send an event to libvirt - at that time the device
> will be removed from libvirt's list of devices.
>
> tl;dr - this is all expected.
>
>
> >
> > # virsh destroy rhel7.2; virsh start rhel7.2 ;sleep 2;  virsh
> > detach-interface rhel7.2 network 52:54:00:98:c4:a0; sleep 2; virsh
> > dumpxml rhel7.2 |grep /interface -B9
> > Domain rhel7.2 destroyed
> >
> > Domain rhel7.2 started
> >
> > Interface detached successfully
> >
> >       <address type='pci' domain='0x0000' bus='0x00' slot='0x06'
> > function='0x0'/>
> >     </controller>
> >     <interface type='network'>
> >       <mac address='52:54:00:98:c4:a0'/>
> >       <source network='default' bridge='virbr0'/>
> >       <target dev='vnet0'/>
> >       <model type='rtl8139'/>
> >       <alias name='net0'/>
> >       <address type='pci' domain='0x0000' bus='0x00' slot='0x03'
> > function='0x0'/>
> >     </interface>
> >
> > When I detach after the vm boot, expand the sleep time to 10, it will
> succeed.
> >
> > # virsh destroy rhel7.2; virsh start rhel7.2 ;sleep 10;  virsh
> > detach-interface rhel7.2 network 52:54:00:98:c4:a0; sleep 2; virsh
> > dumpxml rhel7.2 |grep /interface -B9
> > Domain rhel7.2 destroyed
> >
> > Domain rhel7.2 started
> >
> > Interface detached successfully
> >
> >
> > -------
> > Best Regards,
> > Yalan Zhang
> > IRC: yalzhang
> > Internal phone: 8389413
> >
> > _______________________________________________
> > libvirt-users mailing list
> > libvirt-users at redhat.com
> > https://www.redhat.com/mailman/listinfo/libvirt-users
> >
>
>
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