Re: [Qemu-devel] [PATCH] virtio-scsi: forward scsibus for virtio-scsi-pci.

[Frederic Konrad <fred.konrad@greensocs.com>]

On 11/06/2013 09:21, Michael S. Tsirkin wrote:
> On Tue, Jun 11, 2013 at 08:43:51AM +0200, Frederic Konrad wrote:
>> On 10/06/2013 19:00, Michael S. Tsirkin wrote:
>>> On Mon, Jun 10, 2013 at 11:53:04AM +0200, fred.konrad@greensocs.com wrote:
>>>> From: KONRAD Frederic <fred.konrad@greensocs.com>
>>>>
>>>> This fix a bug with scsi hotplug on virtio-scsi-pci:
>>>>
>>>> As virtio-scsi-pci doesn't have any scsi bus, we need to forward scsi-hot-add
>>>> to the virtio-scsi-device plugged on the virtio-bus.
>>>>
>>>> Reported-by: Alexey Kardashevskiy <aik@ozlabs.ru>
>>>> Signed-off-by: KONRAD Frederic <fred.konrad@greensocs.com>
>>>> ---
>>>>   hw/pci/pci-hotplug.c | 19 +++++++++++++++++--
>>>>   1 file changed, 17 insertions(+), 2 deletions(-)
>>>>
>>>> diff --git a/hw/pci/pci-hotplug.c b/hw/pci/pci-hotplug.c
>>>> index 12287d1..c708752 100644
>>>> --- a/hw/pci/pci-hotplug.c
>>>> +++ b/hw/pci/pci-hotplug.c
>>>> @@ -30,6 +30,8 @@
>>>>   #include "monitor/monitor.h"
>>>>   #include "hw/scsi/scsi.h"
>>>>   #include "hw/virtio/virtio-blk.h"
>>>> +#include "hw/virtio/virtio-scsi.h"
>>>> +#include "hw/virtio/virtio-pci.h"
>>>>   #include "qemu/config-file.h"
>>>>   #include "sysemu/blockdev.h"
>>>>   #include "qapi/error.h"
>>>> @@ -79,13 +81,26 @@ static int scsi_hot_add(Monitor *mon, DeviceState *adapter,
>>>>   {
>>>>       SCSIBus *scsibus;
>>>>       SCSIDevice *scsidev;
>>>> +    VirtIOPCIProxy *virtio_proxy;
>>>>       scsibus = (SCSIBus *)
>>>>           object_dynamic_cast(OBJECT(QLIST_FIRST(&adapter->child_bus)),
>>>>                               TYPE_SCSI_BUS);
>>>>       if (!scsibus) {
>>>> -	error_report("Device is not a SCSI adapter");
>>>> -	return -1;
>>>> +        /*
>>>> +         * Check if the adapter is a virtio-scsi-pci, and forward scsi_hot_add
>>>> +         * to the virtio-scsi-device.
>>>> +         */
>>>> +        if (!object_dynamic_cast(OBJECT(adapter), TYPE_VIRTIO_SCSI_PCI)) {
>>>> +            error_report("Device is not a SCSI adapter");
>>>> +            return -1;
>>>> +        }
>>>> +        virtio_proxy = VIRTIO_PCI(adapter);
>>>> +        adapter = DEVICE(virtio_proxy->bus.vdev);
>>>> +        scsibus = (SCSIBus *)
>>>> +                  object_dynamic_cast(OBJECT(QLIST_FIRST(&adapter->child_bus)),
>>>> +                            TYPE_SCSI_BUS);
>>>> +        assert(scsibus);
>>>>       }
>>>>       /*
>>> By the way I really wonder. pci-hotplug.c was supposed to
>>> be legacy interface.
>>> Is this the only way to add scsi disks?
>>> And are other ways broken, too?
>> Here you can add scsi disks to a given device.
>> I think the other ways add scsi disks to a given bus?
>>
>> Do you see any other?
>>
>> Thanks,
>> Fred
> I don't know, that's why I'm asking.
>
> If it is, that's crazy. There's no reason for
> it to be tied to pci at all.
>
> The commands in pci-hotplug.c are legacy - they don't support things
> like multi root systems and there's no sane way to make them do it.
>
> Your patch probably makes sense for stable, but for 1.6,
> let's fix this properly.

Ok, what do you propose to fix that properly?

If we want to keep the behaviour of drive_add command, I
think we have two solutions:
     A/ Change the scsi_hot_add to check if it is a virtio-scsi-pci 
device and take
         virtio-scsi-device's scsi bus.
     B/ Make somehow virtio-scsi-pci having a scsi-bus
         (and the same in virtio-scsi-device).

I chose A because it seems a lot easier. For the moment B seems not 
possible,
but would it be a cleaner solution? What do you think?

Fred
>
>>>> -- 
>>>> 1.8.1.4