libvirt users - Oct 2018 - Re: This QEMU doesn't support the LSI 53C895A SCSI controller

Hi all,
trying to edit a domain xml to enable an LSI SCSI controller I get the 
following error:

error: unsupported configuration: This QEMU doesn't support the LSI 
53C895A SCSI controller

It is my understanding that the error is raised due to RedHat disabling 
this controller in its own qemu-kvm builds. This seems an unfortunate 
decision, as it makes harder to migrate from VMWare (which uses LSI SCSI 
and SAS adapters) to RH+KVM.

Can anyone elaborate on this decision? It is possible to enable LSI 
controller support in RedHat 7.x? Should I open a BZ against it?

Thanks.

-- 
Danti Gionatan
Supporto Tecnico
Assyoma S.r.l. - www.assyoma.it
email: g.danti@assyoma.it - info@assyoma.it
GPG public key ID: FF5F32A8

On Sat, 2018-09-29 at 15:02 +0200, Gionatan Danti wrote:
> Hi all,
> trying to edit a domain xml to enable an LSI SCSI controller I get the 
> following error:
> 
> error: unsupported configuration: This QEMU doesn't support the LSI 
> 53C895A SCSI controller
> 
> It is my understanding that the error is raised due to RedHat disabling 
> this controller in its own qemu-kvm builds. This seems an unfortunate 
> decision, as it makes harder to migrate from VMWare (which uses LSI SCSI 
> and SAS adapters) to RH+KVM.
> 
> Can anyone elaborate on this decision? It is possible to enable LSI 
> controller support in RedHat 7.x? Should I open a BZ against it?
Your assessment looks correct, and the controller is indeed compiled
out downstream. Filing a BZ sounds like a reasonable next step, but
you might also want to investigate virt-v2v, which I believe will
take care of switching to the more performant virtio-scsi (including
installing the necessary drivers) for you when moving guests off
VMware.

-- 
Andrea Bolognani / Red Hat / Virtualization

On 02/10/2018 09:19, Andrea Bolognani wrote:
> Your assessment looks correct, and the controller is indeed compiled
> out downstream. Filing a BZ sounds like a reasonable next step, but
> you might also want to investigate virt-v2v, which I believe will
> take care of switching to the more performant virtio-scsi (including
> installing the necessary drivers) for you when moving guests off
> VMware.
Hi Andrea, thanks for the reply.

 From my understanding, virt-v2v use virt-win-reg to open the disk image 
and install new drivers in the registry. I am doing a very similar thing 
by manually using virt-win-reg to add the mergeide.reg file to enable 
booting from any IDE controller.

That said, both virt-v2v and manual virt-win-reg have a significant 
shortcoming: when used on non-cleanly-shutdown images, the act of 
opening the NTFS filesystem alters the journal/filesystem state. In one 
planned lab test I found some file to be corrupted after running 
virt-win-reg, and I traced back the cause to the unclean NTFS 
shutdown/mounting.

Adding a supported controller will prevent any issue: even with an 
unclean shutdown, the machine will boot and replay its NTFS journal. If 
needed, it can also run the proper Windows filesystem checking tool 
(chkdsk) which is, as far I know, better positioned to correct any 
filesystem problem.

Am I missing something?
Thanks.

-- 
Danti Gionatan
Supporto Tecnico
Assyoma S.r.l. - www.assyoma.it
email: g.danti@assyoma.it - info@assyoma.it
GPG public key ID: FF5F32A8