On Tue, 31 Jul 2018 15:29:17 +0300 "Michael S. Tsirkin" <mst@xxxxxxxxxx> wrote: > On Mon, Jul 30, 2018 at 05:13:26PM -0600, Alex Williamson wrote: > > v2: > > - Use atomic ops for balloon inhibit counter (Peter) > > - Allow endpoint driver opt-in for ballooning, vfio-ccw opt-in by > > default, vfio-pci opt-in by device option, only allowed for mdev > > devices, no support added for platform as there are no platform > > mdev devices. > > > > See patch 3/4 for detailed explanation why ballooning and device > > assignment typically don't mix. If this eventually changes, flags > > on the iommu info struct or perhaps device info struct can inform > > us for automatic opt-in. Thanks, > > > > Alex > > So this patch seems to block ballooning when vfio is added. > But what if balloon is added and inflated first? Good point. > I'd suggest making qemu_balloon_inhibit fail in that case, > and then vfio realize will fail as well. That might be the correct behavior for vfio, but I wonder about the existing postcopy use case. Dave Gilbert, what do you think? We might need a separate interface for callers that cannot tolerate existing ballooned pages. Of course we'll also need another atomic counter to keep a tally of ballooned pages. Thanks, Alex
