On Tue, 23 Apr 2019 15:41:34 -0400 Farhan Ali <alifm@xxxxxxxxxxxxx> wrote: > > > On 04/23/2019 01:42 PM, Halil Pasic wrote: > > One thing I'm confused about is, that we don't seem to prevent > > new I/O being submitted. That is we could still loop indefinitely > > if we get new IO after the 'kill I/O on the subchannel' is done but > > before the msch() with the disable is issued. > > So the quiesce function will be called in the remove, release functions > and also in the mdev reset callback via an ioctl VFIO_DEVICE_RESET. > > Now the release function is invoked in cases when we hot unplug the > device or the guest is gone (or anything that will close the vfio mdev > file descriptor, I believe). In such scenarios it's really the userspace > which is asking to release the device. Similar for remove, where the > user has to explicitly write to the remove file for the mdev to invoke > it. Under normal conditions no sane userspace should be doing > release/remove while there are still on going I/Os :) So you say userspace has to take care of it. Is this documented somewhere? Does QEMU actually take care of it? > > Me and Conny had some discussion on this in v1 of this patch: > https://marc.info/?l=kvm&m=155437117823248&w=2 > > > > > The 'flush all I/O' parts in the commit message and in the code make > > this even more confusing. > > Maybe...if it's too confusing it could be fixed, but IMHO I don't think > it's a dealbreaker. If anyone else thinks otherwise, I can go ahead and > change it. > I responded to Connie. No it is not a dealbreaker. But I prefer not disseminating false information. [..] Regarding the rest of the points from her, I responded to Connie's follow up as well. Cheers, Halil
