On Fri, May 04, 2012 at 17:28:39 -0600, Eric Blake wrote:
On 05/04/2012 04:40 PM, Jiri Denemark wrote:
When we added the default USB controller into domain XML, we efficiently broke migration to older versions of libvirt that didn't support USB controllers at all (0.9.4 and earlier) even for domains that doesn't use
s/doesn't/don't/
anything that the older libvirt can't provide. We still want to present the default USB controller in any XML seen by a user/app but we can safely remove it from the domain XML used during migration. If we are migrating to a new enough libvirt, it will add the controller XML back, while older libvirt won't be confused with it although it will still tell qemu to create the controller.
Similar approach can be used in the future whenever we find out we always enabled some kind of device without properly advertising it in domain XML.
Memballoon would be such a device, if we care about migration to even older libvirt.
Right.
--- src/qemu/qemu_domain.c | 60 ++++++++++++++++++++++++++++++++++++++++---- src/qemu/qemu_domain.h | 10 +++++-- src/qemu/qemu_driver.c | 21 +++++++++------ src/qemu/qemu_migration.c | 10 ++++--- src/qemu/qemu_process.c | 8 +++--- 5 files changed, 83 insertions(+), 26 deletions(-)
diff --git a/src/qemu/qemu_domain.c b/src/qemu/qemu_domain.c index b105644..3752ddf 100644 --- a/src/qemu/qemu_domain.c +++ b/src/qemu/qemu_domain.c @@ -1227,11 +1227,14 @@ int qemuDomainDefFormatBuf(struct qemud_driver *driver, virDomainDefPtr def, unsigned int flags, + bool compatible, virBuffer *buf)
Rather than adding a new 'compatible' flag and having to adjust _every_ caller, could we instead add a new VIR_DOMAIN_XML_INTERNAL flag to be or'd in to flags only for the callers that care? On the other hand, we'd have to filter that flag back out before calling into domain_conf, so I guess this approach is as good as any.
Yeah, we would need to filter it out and we would need to either move the internal flags enum to a more public place (it's internal to domain_conf.c now) or make another enum and make sure neither of them conflicts with the real flags enum :-) I decided to introduce new bool parameter since the compiler checked are places I need to change for me and it's more explicit so that any new caller of this api needs to explicitly think about the value to pass for compatibility.
+ if (usb && usb->idx == 0 && usb->model == -1) {
Just like memballoon, if we ever want to explicitly represent an XML with no usb controller, we will have to provide <controller type='usb' mode='none'>; but there, the model would not be -1, so this would properly be migrated.
Right and we already have a request to do just this. BTW, I don't explicitly check the PCI address assigned to the controller because the default automatically added USB1 controller must always have PCI address 0:0:1.2. When a domains is configured with different address assigned to the default USB controller, libvirt will refuse to start it.
ACK.
Thanks. I pushed this series. Jirka