On Tue, Jun 18, 2019 at 03:04:40PM -0300, Daniel Henrique Barboza wrote:
Hi,
This is labeled as RFC but it's more like a FYI to let people know and comment beforehand. Shiva sent a 28 patch series last year that implements hotplug/unplug support for PCI multifunction devices [1]. The design motivation of his work was based in a RFC sent to this mailing list back in 2016 [2].
I'll briefly summarize the goals and motivations here. What we have today in Libvirt:
- no hotplug/unplug support for multifunction PCI devices
This is explained in details in [2]. When hotplugging a multifunction device, QEMU will queue the hotplug operation of all non-zero functions and, when function 0 is hotplugged, all functions are hotplugged together. This is true for all archs that supports PCI multifunction devices in QEMU. For unplug it varies: x86 will unplug all functions if any function is unplugged, ppc64 needs to unplug each one.
Do you know anything about why ppc64 & x86 are different in this respect in QEMU. I think it would be desirable to fix QEMU so that unplug works consistently across architectures. These kind of behavioural differences are a cause of pain as x86 gets all the day to day testing & leaving ppc64 to bitrot if it behaves differently. Regards, Daniel -- |: https://berrange.com -o- https://www.flickr.com/photos/dberrange :| |: https://libvirt.org -o- https://fstop138.berrange.com :| |: https://entangle-photo.org -o- https://www.instagram.com/dberrange :|