答复: Some confusion about lsilogic controller

[xingchaochao]

Thank you for your kind reply. This issue involves a qemu bug, 
and the patch has been queued by the qemu community on March 2. 
https://patchwork.kernel.org/project/qemu-devel/patch/20210302133016.1221081-1-liangpeng10@huawei.com/

Regards,
Xingchaochao

-----邮件原件-----
发件人: Daniel P. Berrangé [mailto:berrange at redhat.com] 
发送时间: 2021年2月24日 19:07
收件人: xingchaochao <xingchaochao at huawei.com>
抄送: libvir-list at redhat.com; libvirt-users at redhat.com; liangpeng (H) <liangpeng10 at huawei.com>; Zhangbo (Oscar) <oscar.zhangbo at huawei.com>; Xiexiangyou <xiexiangyou at huawei.com>
主题: Re: Some confusion about lsilogic controller

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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