Some confusion about lsilogic controller

[Daniel P. Berrangé]

On Wed, Feb 24, 2021 at 09:11:03AM +0000, xingchaochao wrote:
> 
> Hello,
> I have been confused by such a phenomenon recently.
> Libvirt is the master branch , and the VM is centos8.2(kernel is 4.18.0-193.el8.aarch64).
> When I hot-plug the scsi disk for a virtual machine without a virtio-scsi controller, libvirt will automatically generate an lsilogic controller for the scsi disk.

snip

> I am confused, why libvirt chooses to generate an lsilogic controller
> for the scsi disk when there is no scsi controller, instead of directly
> reporting an error and exiting the hot plug operation. After all, the
> scsi disk based on the lsilogic controller is not perceived inside
> the virtual machine, and lsilogic will remain in the XML file of the
> virtual machine.

libvirt has no knowledge of what devices the guest OS is able to
support. In this case RHEL8 doesn't support lsilogic, but libvirt
doesn't know this.

Generally a libvirt mgmt application will not rely on the defaults
for choosing devices, and instead use libosinfo to figure out
what devices are likely to be supported and explicitly use those.


Regards,
Daniel
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