Re: [libvirt] [PATCH] qemu: Prevent detaching SCSI controller used by hostdev

Consider a guest started with the following XML snippet: <controller type='scsi' model='virtio-scsi' index='0'/> <hostdev mode='subsystem' type='scsi'> <source> <adapter name='scsi_host0'/> <address bus='0' target='8' unit='1074151456'/>

</source> </hostdev> If we attach/create a virtio-scsi hostdev device but forget to include a virtio-scsi controller, one is silently created for us. (See qemuDomainFindOrCreateSCSIDiskController for context.)

Detaching the hostdev, followed by the controller, works well and the guest behaves appropriately.

If we detach the virtio-scsi controller device first, Libvirt silently detaches any associated hostdevs for us too. But all is not well, as the guest is unable to receive new virtio-scsi devices (the attach commands succeed, but devices never appear within the guest), nor even be shutdown, after this point.

It appears that something is tied up in the host virtio layer.

While I investigate this, we can see if a controller is being used by any hostdevs, and prevent the detach if it would lead us down this path.

$ virsh detach-device guest_one_virtio_scsi scsicontroller.xml error: Failed to detach device from scsicontroller.xml error: operation failed: device cannot be detached: device is busy $ virsh detach-device guest_one_virtio_scsi scsidisk.xml Device detached successfully $ virsh detach-device guest_one_virtio_scsi scsicontroller.xml Device detached successfully Signed-off-by: Eric Farman <farman(a)linux.vnet.ibm.com&gt; Reviewed-by: Bjoern Walk <bwalk(a)linux.vnet.ibm.com&gt; Reviewed-by: Boris Fiuczynski <fiuczy(a)linux.vnet.ibm.com&gt; --- src/qemu/qemu_hotplug.c | 10 ++++++++++ 1 file changed, 10 insertions(+) diff --git a/src/qemu/qemu_hotplug.c b/src/qemu/qemu_hotplug.c index b03e618..5db7abf 100644 --- a/src/qemu/qemu_hotplug.c +++ b/src/qemu/qemu_hotplug.c @@ -4443,6 +4443,7 @@ static bool qemuDomainDiskControllerIsBusy(virDomainObjPtr vm, { size_t i; virDomainDiskDefPtr disk; + virDomainHostdevDefPtr hostdev; for (i = 0; i < vm->def->ndisks; i++) { disk = vm->def->disks[i]; @@ -4465,6 +4466,15 @@ static bool qemuDomainDiskControllerIsBusy(virDomainObjPtr vm, return true; } + for (i = 0; i < vm->def->nhostdevs; i++) { + hostdev = vm->def->hostdevs[i]; + if (!virHostdevIsSCSIDevice(hostdev) || + detach->type != VIR_DOMAIN_CONTROLLER_TYPE_SCSI) + continue; + if (hostdev->info->addr.drive.controller == detach->idx) + return true; + } +

return false; }