Re: [libvirt] [PATCH 5/9] Implement controller hotplugging

On Fri, Sep 18, 2009 at 05:26:12PM +0200, Wolfgang Mauerer wrote: > This enables to hot-add disk controllers without attached > disks into the system. Previously, it was only possible to > (implicitly) add disk controllers in the static machine > configuration. > > Notice that the actual functionality is only available > for qemu at present, but other emulators can be extended > likewise. Any idea what we can do about initial startup? eg, if we start a guest with 1 SCSI controller and 1 disk, and then we've then hotplugged a 2nd controller, and 1 disk. When we later boot or migrate the same guest, we need to have suitable QEMU command line args to make sure we get 2 controllers each with the same disk, rather than 1 controller with 2 disks. I'm not sure how we do this in QEMU, hopefully the existing args support it in some way I've not realized, or failing that the new qdev -device args might help us.

> Signed-off-by: Wolfgang Mauerer <wolfgang.mauerer(a)siemens.com&gt; > Signed-off-by: Jan Kiszka <jan.kiszka(a)siemens.com&gt; > --- > src/domain_conf.c | 26 +++++++++++++++++++++++--- > src/domain_conf.h | 2 ++ > src/libvirt_private.syms | 1 + > src/qemu_driver.c | 21 +++++++++++++++++---- > 4 files changed, 43 insertions(+), 7 deletions(-) > > diff --git a/src/domain_conf.c b/src/domain_conf.c > index d0fda64..ea51fda 100644 > --- a/src/domain_conf.c > +++ b/src/domain_conf.c > @@ -647,7 +647,6 @@ void virDomainRemoveInactive(virDomainObjListPtr doms, > > } > > - > /* Parse the XML definition for a disk > * @param node XML nodeset to parse for disk definition > */ > @@ -2554,6 +2553,27 @@ virDomainDeviceDefPtr virDomainDeviceDefParse(virConnectPtr conn, > #endif > > > +static int virDomainControllerCompare(virDomainControllerDefPtr a, > + virDomainControllerDefPtr b) { > + if (a->pci_addr.bus == b->pci_addr.bus) { > + if (a->pci_addr.domain == b->pci_addr.domain) > + return a->pci_addr.slot - b->pci_addr.slot; > + > + return a->pci_addr.domain - b->pci_addr.domain; > + } > + > + return a->pci_addr.bus - b->pci_addr.bus; > +} > + > + > +int virDomainControllerQSort(const void *a, const void *b) > +{ > + const virDomainControllerDefPtr *da = a; > + const virDomainControllerDefPtr *db = b; > + > + return virDomainControllerCompare(*da, *db); > +} > + I know we used todo this for disk devices, but I'd recommand not going a qsort of devices when hotplugging/unplugging. For hotplug always append to the list, for unplug just shuffle down later devices in the list to fill the hole.