On Fri, 2018-10-05 at 09:54 +0100, Daniel P. Berrangé wrote: > On Fri, Oct 05, 2018 at 10:34:33AM +0200, Jiri Denemark wrote: > > But what if QEMU (or any other hypervisor) marks something (device > > model, machine type) as deprecated and we use that deprecated value as > > our default. Shouldn't we be able to tell about it to our users (here > > runtime warnings could help) when they use such thing explicitly and > > choose a different default value? That would help users with the > > transition and once hypervisor drops support for it completely, fewer > > existing domains will be affected since the recently created ones would > > already use non-deprecated defaults. > > QEMU already emits warnings on stderr whenever something that is > deprecated is used, and those end up in the libvirt log file for > that guest. I don't think that we need to duplicate what QEMU > is already reporting again. Warnings printed on stderr -> users and developers will actually see them, be annoyed by them, eventually cave in and act upon them. Warnings written to a log -> nobody will notice them, until one day things suddenly stop working apparently out of the blue. We might pretend that's not the case, but really, it is. > > So taking "q35" as an example, if QEMU marks i440fx machine types as > > deprecated (they seem to be thinking about it) I don't see that big > > difference[*] in changing the default machine type to "q35". After all > > we will automatically change the default once i440fx is removed > > completely. > > There's no active plans to deprecate or remove i440fx upstream in > QEMU. If a downstream did remove it, then clearly that'll impose > some level of pain on applications. While i440fx itself has not been deprecated and might possibly never be, other machine types (x86's pc-0.10 and pc-0.11, ppc's prep) are in fact already marked as deprecated and will eventually be dropped entirely from QEMU. -- Andrea Bolognani / Red Hat / Virtualization -- libvir-list mailing list libvir-list@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/libvir-list
