[Qemu-devel] [PATCH, RFC] Allow adding empty SCSI controllers

[Wolfgang Mauerer <wolfgang.mauerer@siemens.com>]

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Hi Gerd,

in commit 5b684b5a56e81f6f, you introduced an explicit check
to prevent adding SCSI controllers without attached disks
to the system. Is there any other method to introduce
disk-less controllers into the system? If not, I'd suggest
to remove the check (patch is attached) -- there are some
situations when you want empty SCSI controllers, for instance for
the libvirt hotplug/remove framework currently under development
(see http://article.gmane.org/gmane.comp.emulators.libvirt/19043)

Thanks, Wolfgang

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commit c827742224b9a3a0d9dad0ce36c7e59c1a796ec1
Author: Wolfgang Mauerer <wolfgang.mauerer@siemens.com>
Date:   Tue Dec 15 18:06:19 2009 +0100

    Revert "hotplug: fix "pci_add storage if=scsi""
    
    This reverts commit 5b684b5a56e81f6f88234952fe8ed68010c36e19, and
    also includes some manual adaptions. There are some cases
    where addding an empty SCSI controller to a system makes
    sense, so we should not prohibit this option.
    
    Signed-off-by: Wolfgang Mauerer <wolfgang.mauerer@siemens.com>

diff --git a/hw/lsi53c895a.c b/hw/lsi53c895a.c
index 8b8a80b..eee206b 100644
--- a/hw/lsi53c895a.c
+++ b/hw/lsi53c895a.c
@@ -2103,9 +2103,7 @@ static int lsi_scsi_init(PCIDevice *dev)
     lsi_soft_reset(s);
 
     scsi_bus_new(&s->bus, &dev->qdev, 1, LSI_MAX_DEVS, lsi_command_complete);
-    if (!dev->qdev.hotplugged) {
-        scsi_bus_legacy_handle_cmdline(&s->bus);
-    }
+    scsi_bus_legacy_handle_cmdline(&s->bus);
     vmstate_register(-1, &vmstate_lsi_scsi, s);
     return 0;
 }
diff --git a/hw/pci-hotplug.c b/hw/pci-hotplug.c
index 6e42776..075be31 100644
--- a/hw/pci-hotplug.c
+++ b/hw/pci-hotplug.c
@@ -183,14 +183,10 @@ static PCIDevice *qemu_pci_hot_add_storage(Monitor *mon,
 
     switch (type) {
     case IF_SCSI:
-        if (!dinfo) {
-            monitor_printf(mon, "scsi requires a backing file/device.\n");
-            return NULL;
-        }
         dev = pci_create(bus, devfn, "lsi53c895a");
         if (qdev_init(&dev->qdev) < 0)
             dev = NULL;
-        if (dev) {
+        if (dev && dinfo) {
             if (scsi_hot_add(&dev->qdev, dinfo, 0) != 0) {
                 qdev_unplug(&dev->qdev);
                 dev = NULL;
@@ -204,12 +200,15 @@ static PCIDevice *qemu_pci_hot_add_storage(Monitor *mon,
         }
         dev = pci_create(bus, devfn, "virtio-blk-pci");
         qdev_prop_set_drive(&dev->qdev, "drive", dinfo);
-        if (qdev_init(&dev->qdev) < 0)
-            dev = NULL;
         break;
     default:
         dev = NULL;
     }
+    if (!dev)
+        return NULL;
+    if (dinfo && qdev_init(&dev->qdev) < 0)
+        return NULL;
+
     return dev;
 }