[libvirt] qemu: hotplug virtio_scsi over lsilogic when sicsi controller is not present?

[Liang Yan]

On 7/14/17 3:56 AM, Martin Kletzander wrote:
> On Tue, Jul 11, 2017 at 03:47:55PM -0400, Liang Yan wrote:
>> Hi,
>>
>> We hit some problems when we attached some lun devices in our vm, turns
>> out that libvirt created lsilogic scsi controller automatically for
>> these scsi devices, however these device works well under virtio_scsi
>> controller.
>>
>> the current code logic is check lsilogic first, if qemu could not
>> support it, then check virtio_scsi, however is it better to check
>> virtio_scsi earlier? since it is supported better in qemu level?
>>
>
> It is not in older QEMUs which we need to stay compatible with.
>
Yes, Peter said similar things that kernel may not include newer driver.
>> I am wondering which solution is better?
>> 1. simple switch sequence and check virtio_scsi first
>>
>
> We can't do that.  We have to keep parsing older XMLs (that did not have
> the model in them) the same way as we were before so that we keep stable
> guest ABI.
>
>> 2. add extra option for "virsh attach-disk" to choose specific
>> controller type
>>
>
> Or you can first attach the controller and then attach-device with the
> xml that specifies that particular controller.  attach-disk is a
> syntactic sugar for attach-device IIRC.
>
Yes, this is our current workaround.  Some users are just wondering if
could finish this process by command line(attach-disk) in one step. I
checked the options of attach-disk that "-targetbus" is a close one but
focus on high level bus controller. 

Anyway, thanks for the response, I think what I need to do now is update
our document to make it more clearly. Please let me know if you have
different decision in the future.

Thanks,
Liang

>> Thanks,
>> Liang
>>
>>
>> ====================================
>> Code part is like below
>>
>> qemu_hotplug.c  qemuDomainFindOrCreateSCSIDiskController
>>
>>    /* No SCSI controller present, for backward compatibility we
>>     * now hotplug a controller */
>>    if (VIR_ALLOC(cont) < 0)
>>        return NULL;
>>    cont->type = VIR_DOMAIN_CONTROLLER_TYPE_SCSI;
>>    cont->idx = controller;
>>    cont->model = -1;
>>
>>    VIR_INFO("No SCSI controller present, hotplugging one");
>>    if (qemuDomainAttachControllerDevice(driver,
>>
>>
>>
>> qemu_domain_address.c  qemuDomainSetSCSIControllerModel
>>
>>        if (qemuDomainIsPSeries(def)) {
>>            *model = VIR_DOMAIN_CONTROLLER_MODEL_SCSI_IBMVSCSI;
>>        } else if (virQEMUCapsGet(qemuCaps, QEMU_CAPS_SCSI_LSI)) {
>>            *model = VIR_DOMAIN_CONTROLLER_MODEL_SCSI_LSILOGIC;
>>        } else if (virQEMUCapsGet(qemuCaps, QEMU_CAPS_VIRTIO_SCSI)) {
>>            *model = VIR_DOMAIN_CONTROLLER_MODEL_SCSI_VIRTIO_SCSI;
>>        } else {
>>            virReportError(VIR_ERR_INTERNAL_ERROR, "%s",
>>                           _("Unable to determine model for scsi
>> controller"));
>>            return -1;
>>
>>
>> -- 
>> libvir-list mailing list
>> libvir-list at redhat.com
>> https://www.redhat.com/mailman/listinfo/libvir-list


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