On Mon, Jul 06, 2015 at 10:06:50AM +0800, Hong Bo Li wrote: > > > On 7/5/2015 2:25, Michael S. Tsirkin wrote: > >On Fri, Jul 03, 2015 at 07:09:59PM +0800, Hong Bo Li wrote: > >>>But I would like to note that pci device drivers require driver handshake > >>>before device goes away. > >>>IIUC s390 hotplug is immediate, which is a problem. > >>>Maybe doing the change will help make sure device removal is acked > >>>by guest before it happens? > >>> > >>I did some prototype today. If define zpci first, the progress of unplug > >>will get complicated. > >The point is that you don't have to remove the zpci device at all. > >Remove pci device from zpci. > > > >I think the complication you refer to is the guest ack of > >the removal, isn't it? > >It's complicated, but it has a chance to actually work with > >pci device drivers. > > > >This, as opposed to just removing the device whenever host > >tells us to. > > This patch supports the ack in this way: > After unplugging, the guest will do some cleanup work and disable the zpci > device. > The "is_unplugged" flag in this patch is used to do this ack. Only after the > device > be disabled, we can remove the zpci device from list and do unparent. > > The complication I mean is: > 1. If we define zpci first, the user can unplug a s390 pci device in two ways: > a) unplug the vfio pci device first, unplug the zpci device second. > If the user only tell us to unplug the vfio pci, after the ack, we > will > still need to wait for the unplug zpci cmd from user, before that, > we have to maintain a useless zpci in list. > > b) Unplug the zpci device directly. This will cause the unplugging of > vfio pci > automatically. Then on s390, we have a different unplug cmd comparing to > other platform. > > 2. If we define vfio pci first, the user can unplug a s390 pci device in two > ways: > a) Unplug the zpci first, unplug the vfio pci device second. > We don't need to maintain the extra s390 zpci structure, after ack, we > can > remove the zpci from list and do unparent. > b) Unplug the vfio pci directly. This will cause the unplugging of zpci > automatically. Then on s390, we have a same unplug cmd comparing to > other platform.
You can do the automatic unplug of zpci in 1 as well, can you not? > The ack of these two methods are the same. > > > >>So I prefer defining vfio pci first. > >>And it looks like the vfio pci is the basic device, if we want this > >>vfio pci to work on s390, we have to define a zpci device to give some > >>additional information to it. > >if vfio connects to the bus internal to zpci, it can get > >things from the bus in a natural way. > > > >If zpci is connected to vfio, it becomes much messier. > > > > For these two ways, the vfio pci both connect to the s390 pci root bus. > And zpci devices connect to the s390-pci-fac-bus, there is no difference. What if you don't specify zpci? Does vfio still work? If no then we have to conclude that vfio is connected through zpci not alongside it. -- MST
