Re: [libvirt] [Xen-devel] [FOR 1.3.0 PATCH] conf: add net device prefix for Xen

On 02/22/2016 04:15 PM, Joao Martins wrote: > > On 12/08/2015 04:06 PM, Jim Fehlig wrote: >> Daniel P. Berrange wrote: >>> On Mon, Dec 07, 2015 at 10:59:32PM -0700, Jim Fehlig wrote: >>>> On 12/07/2015 11:52 AM, Daniel P. Berrange wrote: >>>>> On Mon, Dec 07, 2015 at 09:42:21AM -0700, Jim Fehlig wrote: >>>>>> In commit d2e5538b1, the libxl driver was changed to copy interface >>>>>> names autogenerated by libxl to the corresponding network def in the >>>>>> domain's virDomainDef object. The copied name is freed when the domain >>>>>> transitions to the shutoff state. But when migrating a domain, the >>>>>> autogenerated name is included in the XML sent to the destination host. >>>>>> It is possible an interface with the same name already exists on the >>>>>> destination host, causing migration to fail. Indeed the Xen project's >>>>>> OSSTEST CI already encountered such a failure. >>>>>> >>>>>> This patch defines another VIR_NET_GENERATED_PREFIX for Xen, allowing >>>>>> the autogenerated names to be excluded when parsing and formatting >>>>>> inactive config. >>>>>> >>>>>> Signed-off-by: Jim Fehlig <jfehlig(a)suse.com&gt; >>>>>> --- >>>>>> >>>>>> This is an alternative approach to Joao's fix for this regression >>>>>> >>>>>> https://www.redhat.com/archives/libvir-list/2015-December/msg00197.html >>>>>> >>>>>> I think it is the same approach used by the qemu driver. My only >>>>>> reservation is that it expands the potential for clashes with >>>>>> user-defined names. I.e. with this change both 'vnet' and 'vif' are >>>>>> reserved prefixes. >>>>> Hmm, yes, tricky one. >>>>> >>>>> If we only care about XML parsing, then you could register a post >>>>> parse callback instead to do this. >>>> AFAIK, XML parsing is all that's in play here. >>>> >>>>> I'm not clear why we also have it in the virDomainNetDefFormat >>>>> method - and we can't solve that with a post-parse callback. >>>>> >>>>> >>>>> The other option would be to make the reserved prefix be a >>>>> capability that the parser/formatter could read. >>>> This seems like the best option, since a post-parse callback doesn't solve the >>>> problem in virDomainNetDefFormat. It also has the upshot of making the prefix >>>> visible and known to users. But I doubt such a change is suitable during 1.3.0 >>>> freeze. With the freeze in mind, seems the best solution to the libxl migration >>>> regression is revert d2e5538b1. It can be added again post-1.3.0 release, after >>>> adding the prefix to capabilities. >>>> >>>> DV, since you may be making the release soon, feel free to revert d2e5538b1 if >>>> you agree. >>> Yeah, just go ahead & revert it Jim, DV isn't doing the releae until >>> tomorrow morning >> I've pushed the revert. >> >> Joao, sorry for yanking this for 1.3.0. We can get it in 1.3.1, after exposing >> the prefix in capabilities. >> > Hey Jim, > > I had the impression we had pushed this back in (i.e. cherry-picking d2e5538) > but I was double checking and that's doesn't seem to be case. In adding support > for the prefix in capabilities I found out one issue on the migration failure > path leading to dereferencing a NULL pointer on the destination. If you agree > could we squash the following chunk in addition to the cherry-pick of d2e5538: > > diff --git a/src/libxl/libxl_domain.c b/src/libxl/libxl_domain.c > index 63c5b24..f73bfb3 100644 > --- a/src/libxl/libxl_domain.c > +++ b/src/libxl/libxl_domain.c > @@ -768,7 +768,7 @@ libxlDomainCleanup(libxlDriverPrivatePtr driver, > for (i = 0; i < vm->def->nnets; i++) { > virDomainNetDefPtr net = vm->def->nets[i]; > > - if (STRPREFIX(net->ifname, "vif")) > + if (net->ifname && STRPREFIX(net->ifname, "vif")) > VIR_FREE(net->ifname); > } > } > diff --git a/src/libxl/libxl_driver.c b/src/libxl/libxl_driver.c > index 3f4457f..5479441 100644 > --- a/src/libxl/libxl_driver.c > +++ b/src/libxl/libxl_driver.c > @@ -5590,7 +5590,7 @@ static virHypervisorDriver libxlHypervisorDriver = { > .domainGetJobStats = libxlDomainGetJobStats, /* 1.3.1 */ > .domainMemoryStats = libxlDomainMemoryStats, /* 1.3.0 */ > .domainGetCPUStats = libxlDomainGetCPUStats, /* 1.3.0 */ > - .domainInterfaceStats = libxlDomainInterfaceStats, /* 1.3.0 */ > + .domainInterfaceStats = libxlDomainInterfaceStats, /* 1.3.2 */ > .connectDomainEventRegister = libxlConnectDomainEventRegister, /* 0.9.0 */ > .connectDomainEventDeregister = libxlConnectDomainEventDeregister, /* 0.9.0 */ > .domainManagedSave = libxlDomainManagedSave, /* 0.9.2 */ > > > Or do you think it should be deferred to 1.3.3 ? I wanted to ask you about this on the recent Xen+libvirt+OpenStack sync. Thanks for checking. It would be a shame if this patch didn't make 1.3.2 since all of your prerequisite work is in, but perhaps a new patch is best given the changes?

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