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

From: Frederic Konrad
Subject: Re: [Qemu-devel] [PATCH] virtio-scsi: forward scsibus for virtio-scsi-pci.
Date: Tue, 11 Jun 2013 09:32:05 +0200
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:17.0) Gecko/20130311 Thunderbird/17.0.4

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 *)
      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?

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?



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