Re: [libvirt] [PATCH v3 10/12] qemu: Add hotpluging support for PCI devices on S390 guests

在 2018/8/18 上午12:10, Andrea Bolognani 写道: > On Tue, 2018-08-07 at 17:10 +0800, Yi Min Zhao wrote: > > This commit adds hotplug support for PCI devices on S390 guests. > > There's no need to implement hot unplug for zPCI as QEMU implements > > an unplug callback which will unplug both PCI and zPCI device in a > > cascaded way. > > It looks like you ended up implementing explicit hot unplug at > least for controllers. I think perhaps it would be a good idea > to implement it for all devices instead of relying on QEMU's > own unplug cascading so that we have more control over the whole > process. It's different between controller and device. And we only hot unplug pci controller, not for all controller types. In addition, we only could do hot-unplug one time, either zpci device or corresponding pci device. It's due to Qemu logic. Qemu will hot-unplug zpci device automatically while doing hotplug pci device, and vice versa.

> So, I'm very much not familiar with the hotplug code and seeing > changes to stuff like qemuDomainAttachDiskGeneric() makes me a bit > uncomfortable :) > > I can't spot anything obviously wrong in your changes, but I think > perhaps you might want to enter and exit the monitor separately > for the zpci device and for the virtio device? I'm not sure that's > useful at all, but network devices for example seems to follow > that pattern... It would be great if someone with more experience > in this area could provide a review. We have to add zpci device firstly and add corresponding pci device secondly. Do you think it's redundant to call monitor twice to add two devices?