On Fri, Jul 26, 2019 at 10:05:02AM +0100, Burakov, Anatoly wrote: > Hi all, > > While investigating this bug: > > https://bugs.dpdk.org/show_bug.cgi?id=284 > > I came across a realization that, when primary process dies, very little > actually works. There are some documented issues that are already present > when secondary processes keep running, like memory map becoming static, and > hotplug not working any more. > > What is less known (and documented) is that VFIO also completely stops > working when initializing processes, because some time since 18.xx releases, > we've fixed a long standing VFIO-related bug that had to do with creating > new containers every time a secondary is run - secondary processes will now > reuse the primary process's container instead. > > Meaning, for VFIO devices, secondary process *initialization* will fail > after primary process has died, because there is no longer a process from > which we can get the VFIO container from. Things will still sort-of work > with igb_uio or in vfio-noiommu mode, but again - no memory map updates, no > hotplug, potentially other things that i don't even know about. > > Therefore, while ideally we would like people to have primary process always > running, the least we can do to avoid documenting a complex matrix of "what > is supported in which case" is to disallow secondary process initialization > after primary process has died. > > ("disallow" as in "explicitly document it as unsupported", although we can > also outright prevent it if we want - rte_eal_primary_proc_alive() will tell > us that) > Documenting this limitation seems a good thing to do. I'm not sure that it's worthwhile trying to make the scenario (of running a secondary after a primary has terminated) supported.
/Bruce
