[libvirt] [PATCH 1/3] qemu: hot-plug: Fix broken SCSI disk hot-plug

[Marc Hartmayer]

The commit "qemu: hot-plug: Assume support for -device in
qemuDomainAttachSCSIDisk" dropped the code for the automatic SCSI
controller creation used in SCSI disk hot-plugging. If we are
hot-plugging a SCSI disk to a domain and there is no proper SCSI
controller defined, it results in an "error: internal error: Could not
find scsi controller with index X required for device" error.

For that reason reverting a hunk of the commit
d4d32005d6e8b2cc0a2f26b483ca1de10171db6d.

This patch also adds an extra comment to the code to clarify the
loop.

Reviewed-by: Boris Fiuczynski <fiuczy at linux.vnet.ibm.com>
Reviewed-by: Bjoern Walk <bwalk at linux.vnet.ibm.com>
Signed-off-by: Marc Hartmayer <mhartmay at linux.vnet.ibm.com>
---
 src/qemu/qemu_hotplug.c | 20 ++++++++++++++++++++
 1 file changed, 20 insertions(+)

diff --git a/src/qemu/qemu_hotplug.c b/src/qemu/qemu_hotplug.c
index e0b8230..5e6a8cb 100644
--- a/src/qemu/qemu_hotplug.c
+++ b/src/qemu/qemu_hotplug.c
@@ -544,7 +544,9 @@ qemuDomainAttachSCSIDisk(virConnectPtr conn,
                          virDomainObjPtr vm,
                          virDomainDiskDefPtr disk)
 {
+    size_t i;
     qemuDomainObjPrivatePtr priv = vm->privateData;
+    virDomainControllerDefPtr cont = NULL;
     char *drivestr = NULL;
     char *devstr = NULL;
     int ret = -1;
@@ -561,6 +563,24 @@ qemuDomainAttachSCSIDisk(virConnectPtr conn,
         goto error;
     }
 
+    /* Let's make sure the disk has a controller defined and loaded before
+     * trying to add it. The controller used by the disk must exist before a
+     * qemu command line string is generated.
+     *
+     * Ensure that the given controller and all controllers with a smaller index
+     * exist; there must not be any missing index in between.
+     */
+    for (i = 0; i <= disk->info.addr.drive.controller; i++) {
+        cont = qemuDomainFindOrCreateSCSIDiskController(driver, vm, i);
+        if (!cont)
+            goto error;
+    }
+
+    /* Tell clang that "cont" is non-NULL.
+       This is because disk->info.addr.driver.controller is unsigned,
+       and hence the above loop must iterate at least once. */
+    sa_assert(cont);
+
     if (qemuAssignDeviceDiskAlias(vm->def, disk, priv->qemuCaps) < 0)
         goto error;
 
-- 
2.5.5