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[libvirt] [RFC PATCH] qemu: Shorten SCSI hostdev alias to avoid QEMU failure



The alias for hostdevs of type SCSI can be too long for QEMU if
larger LUNs are encountered. Here's a real life example:

    <hostdev mode='subsystem' type='scsi' managed='no'>
      <source>
        <adapter name='scsi_host0'/>
        <address bus='0' target='19' unit='1088634913'/>
      </source>
      <address type='drive' controller='0' bus='0' target='0' unit='0'/>
    </hostdev>

this results in a too long drive id, resulting in QEMU yelling

Property 'scsi-generic.drive' can't find value 'drive-hostdev-scsi_host0-0-19-1088634913'

This commit changes the alias back to the default hostdev$(index)
scheme.

Signed-off-by: Viktor Mihajlovski <mihajlov linux vnet ibm com>
---

Actually this is highlighting a larger issue. Apparently QEMU ids
are limited to a length of 32 bytes. This means that SCSI based
drives are also in danger to exceed this limit.
We should consider to use a drive index for controller-attached
disks for alias generation instead of the verbose
drive-$bustype-$busaddress schema.

 src/qemu/qemu_command.c                            |   10 +---------
 .../qemuxml2argv-hostdev-scsi-boot.args            |    4 ++--
 .../qemuxml2argv-hostdev-scsi-lsi.args             |    4 ++--
 .../qemuxml2argv-hostdev-scsi-readonly.args        |    4 ++--
 .../qemuxml2argv-hostdev-scsi-virtio-scsi.args     |    4 ++--
 5 files changed, 9 insertions(+), 17 deletions(-)

diff --git a/src/qemu/qemu_command.c b/src/qemu/qemu_command.c
index 879aed8..8c8bef2 100644
--- a/src/qemu/qemu_command.c
+++ b/src/qemu/qemu_command.c
@@ -818,16 +818,8 @@ qemuAssignDeviceHostdevAlias(virDomainDefPtr def, virDomainHostdevDefPtr hostdev
         }
     }
 
-    if (hostdev->source.subsys.type == VIR_DOMAIN_HOSTDEV_SUBSYS_TYPE_SCSI) {
-        if (virAsprintf(&hostdev->info->alias, "hostdev-%s-%d-%d-%d",
-                        hostdev->source.subsys.u.scsi.adapter,
-                        hostdev->source.subsys.u.scsi.bus,
-                        hostdev->source.subsys.u.scsi.target,
-                        hostdev->source.subsys.u.scsi.unit) < 0)
-            return -1;
-    } else if (virAsprintf(&hostdev->info->alias, "hostdev%d", idx) < 0) {
+    if (virAsprintf(&hostdev->info->alias, "hostdev%d", idx) < 0)
         return -1;
-    }
 
     return 0;
 }
diff --git a/tests/qemuxml2argvdata/qemuxml2argv-hostdev-scsi-boot.args b/tests/qemuxml2argvdata/qemuxml2argv-hostdev-scsi-boot.args
index cd22672..ba1e6c6 100644
--- a/tests/qemuxml2argvdata/qemuxml2argv-hostdev-scsi-boot.args
+++ b/tests/qemuxml2argvdata/qemuxml2argv-hostdev-scsi-boot.args
@@ -4,6 +4,6 @@ unix:/tmp/test-monitor,server,nowait -no-acpi \
 -device virtio-scsi-pci,id=scsi0,bus=pci.0,addr=0x3 -usb \
 -drive file=/dev/HostVG/QEMUGuest2,if=none,id=drive-ide0-0-0 \
 -device ide-drive,bus=ide.0,unit=0,drive=drive-ide0-0-0,id=ide0-0-0 \
--drive file=/dev/sg0,if=none,id=drive-hostdev-scsi_host0-0-0-0 \
--device scsi-generic,bus=scsi0.0,channel=0,scsi-id=4,lun=8,drive=drive-hostdev-scsi_host0-0-0-0,id=hostdev-scsi_host0-0-0-0,bootindex=1 \
+-drive file=/dev/sg0,if=none,id=drive-hostdev0 \
+-device scsi-generic,bus=scsi0.0,channel=0,scsi-id=4,lun=8,drive=drive-hostdev0,id=hostdev0,bootindex=1 \
 -device virtio-balloon-pci,id=balloon0,bus=pci.0,addr=0x4
diff --git a/tests/qemuxml2argvdata/qemuxml2argv-hostdev-scsi-lsi.args b/tests/qemuxml2argvdata/qemuxml2argv-hostdev-scsi-lsi.args
index 06f7938..2cbf9be 100644
--- a/tests/qemuxml2argvdata/qemuxml2argv-hostdev-scsi-lsi.args
+++ b/tests/qemuxml2argvdata/qemuxml2argv-hostdev-scsi-lsi.args
@@ -4,6 +4,6 @@ unix:/tmp/test-monitor,server,nowait -no-acpi -boot c \
 -device lsi,id=scsi0,bus=pci.0,addr=0x3 -usb \
 -drive file=/dev/HostVG/QEMUGuest2,if=none,id=drive-ide0-0-0 \
 -device ide-drive,bus=ide.0,unit=0,drive=drive-ide0-0-0,id=ide0-0-0 \
--drive file=/dev/sg0,if=none,id=drive-hostdev-scsi_host0-0-0-0 \
--device scsi-generic,bus=scsi0.0,scsi-id=7,drive=drive-hostdev-scsi_host0-0-0-0,id=hostdev-scsi_host0-0-0-0 \
+-drive file=/dev/sg0,if=none,id=drive-hostdev0 \
+-device scsi-generic,bus=scsi0.0,scsi-id=7,drive=drive-hostdev0,id=hostdev0 \
 -device virtio-balloon-pci,id=balloon0,bus=pci.0,addr=0x4
diff --git a/tests/qemuxml2argvdata/qemuxml2argv-hostdev-scsi-readonly.args b/tests/qemuxml2argvdata/qemuxml2argv-hostdev-scsi-readonly.args
index ea2f7af..8c274a9 100644
--- a/tests/qemuxml2argvdata/qemuxml2argv-hostdev-scsi-readonly.args
+++ b/tests/qemuxml2argvdata/qemuxml2argv-hostdev-scsi-readonly.args
@@ -4,6 +4,6 @@ unix:/tmp/test-monitor,server,nowait -no-acpi -boot c \
 -device virtio-scsi-pci,id=scsi0,bus=pci.0,addr=0x3 -usb \
 -drive file=/dev/HostVG/QEMUGuest2,if=none,id=drive-ide0-0-0 \
 -device ide-drive,bus=ide.0,unit=0,drive=drive-ide0-0-0,id=ide0-0-0 \
--drive file=/dev/sg0,if=none,id=drive-hostdev-scsi_host0-0-0-0,readonly=on \
--device scsi-generic,bus=scsi0.0,channel=0,scsi-id=4,lun=8,drive=drive-hostdev-scsi_host0-0-0-0,id=hostdev-scsi_host0-0-0-0 \
+-drive file=/dev/sg0,if=none,id=drive-hostdev0,readonly=on \
+-device scsi-generic,bus=scsi0.0,channel=0,scsi-id=4,lun=8,drive=drive-hostdev0,id=hostdev0 \
 -device virtio-balloon-pci,id=balloon0,bus=pci.0,addr=0x4
diff --git a/tests/qemuxml2argvdata/qemuxml2argv-hostdev-scsi-virtio-scsi.args b/tests/qemuxml2argvdata/qemuxml2argv-hostdev-scsi-virtio-scsi.args
index b92afc7..a7d6789 100644
--- a/tests/qemuxml2argvdata/qemuxml2argv-hostdev-scsi-virtio-scsi.args
+++ b/tests/qemuxml2argvdata/qemuxml2argv-hostdev-scsi-virtio-scsi.args
@@ -4,6 +4,6 @@ unix:/tmp/test-monitor,server,nowait -no-acpi -boot c \
 -device virtio-scsi-pci,id=scsi0,bus=pci.0,addr=0x3 -usb \
 -drive file=/dev/HostVG/QEMUGuest2,if=none,id=drive-ide0-0-0 \
 -device ide-drive,bus=ide.0,unit=0,drive=drive-ide0-0-0,id=ide0-0-0 \
--drive file=/dev/sg0,if=none,id=drive-hostdev-scsi_host0-0-0-0 \
--device scsi-generic,bus=scsi0.0,channel=0,scsi-id=4,lun=8,drive=drive-hostdev-scsi_host0-0-0-0,id=hostdev-scsi_host0-0-0-0 \
+-drive file=/dev/sg0,if=none,id=drive-hostdev0 \
+-device scsi-generic,bus=scsi0.0,channel=0,scsi-id=4,lun=8,drive=drive-hostdev0,id=hostdev0 \
 -device virtio-balloon-pci,id=balloon0,bus=pci.0,addr=0x4
-- 
1.7.9.5


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