[libvirt] [PATCH 0/3] qemu: make runtime validation of NetDefs more consistent

[Michal Prívozník]

On 9/13/19 4:52 PM, Laine Stump wrote:
> There is some validation of NetDefs (<interface>) that can't be done
> until runtime, due to not knowing the exact configuration until that
> time. This needs to happen in 3 places: 1) in the qemu commandline
> when a new guest is started, 2) when an <interface> is hotplugged, and
> 3) when an <interface> is updated. Until now, there some (but not all)
> validation copy-pasted between (1) and (2), and none of that was
> present for (3). These patches move all the validation from (1) (which
> is the most complete) into a separate function, and then call that
> function from all three places, so the exact same validation is done
> in all cases.
> 
> (These patches are a followup to a patch I sent *long* ago in a naive
> attempt to fix https://bugzilla.redhat.com/1502754 - my original patch
> did fix the problem when starting a guest with an invalid <interface>
> config, but not when hotplugging or updating such an interface.)
> 
> NB: I noticed that if someone tries to specify <bandwidth> for an
> interface type that doesn't support it, we only give a warning, not an
> error, due to a fear that there are existing management apps that add
> <bandwidth> to all types of interfaces, and we don't want them to
> suddenly fail to run (I got this info from the BZ associated with the
> commit that added the warning). This seems to me to be going a bit too
> far - I think that (at least upstream) we should turn this into an
> error, and let the regression testing of said management apps catch
> the behavior change so they can fix their code. (insert
> Kermit-drinking-coffee meme here)

Yes, that was exactly the reasoning we had when introducing the warning.
Initially, when I implemented QoS it did not error out on unsupported
interface type, but I guess we can do so now.

> 
> 
> Laine Stump (3):
>   conf: make arg to virDomainNetGetActualVirtPortProfile() a const
>   qemu: move runtime netdev validation into a separate function
>   qemu: call common NetDef validation for hotplug and device update
> 
>  src/conf/domain_conf.c  |  2 +-
>  src/conf/domain_conf.h  |  2 +-
>  src/qemu/qemu_command.c | 52 +--------------------------
>  src/qemu/qemu_domain.c  | 80 +++++++++++++++++++++++++++++++++++++++++
>  src/qemu/qemu_domain.h  |  4 +++
>  src/qemu/qemu_hotplug.c | 32 +++++------------
>  6 files changed, 95 insertions(+), 77 deletions(-)
> 

Reviewed-by: Michal Privoznik <mprivozn at redhat.com>  but please see my
comment to 2/3 before pushing.

Michal