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

[Michael S. Tsirkin]

On Thu, Jun 13, 2013 at 09:34:30AM +0200, Frederic Konrad wrote:
> On 13/06/2013 09:23, Michael S. Tsirkin wrote:
> >On Thu, Jun 13, 2013 at 04:46:09PM +1000, Alexey Kardashevskiy wrote:
> >>On 06/13/2013 04:28 PM, Frederic Konrad wrote:
> >>>On 12/06/2013 13:21, Alexey Kardashevskiy wrote:
> >>>>On 06/12/2013 07:16 PM, Michael S. Tsirkin wrote:
> >>>>>On Wed, Jun 12, 2013 at 07:04:48PM +1000, Alexey Kardashevskiy wrote:
> >>>>>>On 06/12/2013 07:03 PM, Michael S. Tsirkin wrote:
> >>>>>>>On Wed, Jun 12, 2013 at 08:15:17AM +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.
> >>>>>>>>
> >>>>>>>>Cc: address@hidden
> >>>>>>>>Reported-by: Alexey Kardashevskiy <address@hidden>
> >>>>>>>>Reviewed-by: Andreas Färber <address@hidden>
> >>>>>>>>Signed-off-by: KONRAD Frederic <address@hidden>
> >>>>>>>Acked-by: Michael S. Tsirkin <address@hidden>
> >>>>>>>
> >>>>>>>Note: we don't seem to have any decent way to
> >>>>>>>add disks to devices: no QMP interface,
> >>>>>>>pci address is required instead of using an id ...
> >>>>>>>
> >>>>>>>Anyone can be bothered to fix this?
> >>>>>>Actually PCI address is not always required, this field (we are talking
> >>>>>>about "drive_add"?) is ignored when "if=none".
> >>>>>>
> >>>>>Then documentation in hmp-commands.hx is wrong, isn't it?
> >>>>>Add that to the list.
> >>>>>
> >>>>>if=none can't be actually used to hot-add
> >>>>>a disk to a device, can it? It creates a disc and assumes you will
> >>>>>use it by a device created later.
> >>>>Yep. I run QEMU with -device "virtio-scsi-pci,id=device0" and then do in
> >>>>console:
> >>>>drive_add auto file=virtimg/fc18guest,if=none,id=bar1
> >>>>device_add scsi-disk,bus=device0.0,drive=bar1
> >>>>
> >>>>Pretty hot plug :)
> >>>I thought you use drive_add 0 if=scsi?
> >>
> >>That's the other option, I posted a bug but I did not actually try the fix
> >>till now :)
> >>
> >>It works now if I run QEMU with "-device virtio-scsi-pci" and do this in
> >>qemu console:
> >>drive_add 0 file=virtimg/fc18guest
> >>
> >>No extra parameters or anything, cool, thanks, and :)
> >>
> >>Tested-by: Alexey Kardashevskiy <address@hidden>
> >>
> >>
> >>The only problem with it that it still wants PCI SCSI adapter while
> >>spapr-vscsi is VIO device so if the guest kernel does not have virtio-scsi
> >>support, I have to do what I described in the quote but this is a different
> >>story.
> >Okay.  How about:
> >- document that pci_addr is optional in hmp
> >- if no pci_addr assume if=none
> >- add drive_add to qmp without the pci_addr and if options
> >
> >We are left with the bus=device0.0 syntax for device_add which is also
> >gross - user asked for device0, the .0 part is qemu internals exposed to
> >users.
> >How about teaching qdev that if there's a single bus under a device,
> >naming the device itself should be identical?
> 
> Yes why not seems a good idea, but you'll pass it through bus= option?
> >This will solve the problem neatly without virtio specific hacks,
> >won't it?
> 
> The issue here is command line back-compatibility for pci_addr,
> which won't be solved with
> the "single bus" idea?

Why not? This code:
    scsibus = (SCSIBus *)
        object_dynamic_cast(OBJECT(QLIST_FIRST(&adapter->child_bus)),
                            TYPE_SCSI_BUS);
should be replaced with code from qdev that we'll write
that goes down the chain as long as there's 1 device
on each bus, looking for a device of the appropriate type.

> >
> >>
> >>>>
> >>>>>>>>---
> >>>>>>>>   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);
> >>>>>>>>       }
> >>>>>>>>         /*
> >>
> >>-- 
> >>Alexey