libvirt users - Mar 2019 - why attach-disk can't be effective when the guest is booting

Hi,
      When i use "virsh attach-device rhel disk.xml" when the guest is
booting,then i can't find the disk in the guest after booting.But i can
find it by "virsh domblklist rhel",and when i want to detach it from
the
guest and use "virsh detach-disk rhel vdb", i still can find the disk
by
"virsh domblklist rhel"
    The disk.xml is like:
<disk type="file" device="disk">
<driver name='qemu' type='raw' cache='none'/>
<source file="/var/lib/libvirt/images/foo.img"/>
<target dev="vdb" bus="virtio"/>
</disk>

Libvirt-release is 5.0.0.4 and the qemu-kvm release is 3.1.0

So i want to know why it failed to attach-disk when booting,and why we design
in this way.Maybe it's better to return failure if we can't use it like
this.

On Thu, Mar 07, 2019 at 05:15:49PM +0800, Jianan Gao
wrote:
> Hi,
>       When i use "virsh attach-device rhel disk.xml" when the
guest is
> booting,then i can't find the disk in the guest after booting.But i can
> find it by "virsh domblklist rhel",and when i want to detach it
from the
> guest and use "virsh detach-disk rhel vdb", i still can find the
disk by
> "virsh domblklist rhel"
>     The disk.xml is like:
> <disk type="file" device="disk">
> <driver name='qemu' type='raw' cache='none'/>
> <source file="/var/lib/libvirt/images/foo.img"/>
> <target dev="vdb" bus="virtio"/>
> </disk>
> 
> Libvirt-release is 5.0.0.4 and the qemu-kvm release is 3.1.0
> 
> So i want to know why it failed to attach-disk when booting,and why we
design
> in this way.Maybe it's better to return failure if we can't use it
like
> this.
Hotplug uses ACPI and thus relies on the guest OS to be processing ACPI
hotplug requests. If the OS hasn't initialized sufficiently then it is
possible it might miss th ACPI event, though I'd hope well written OS
would cope wit hthis & catch up later. In any guest its a guest OS problem.

Regards,
Daniel
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