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

[Frederic Konrad]

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, address@hidden wrote:
> > > > From: KONRAD Frederic <address@hidden>
> > > >
> > > > 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 <address@hidden>
> > > > Signed-off-by: KONRAD Frederic <address@hidden>
> > > > ---
> > > >   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