* Alex Williamson (alex.williamson@xxxxxxxxxx) wrote: > 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, For postcopy, preinflation isn't a problem; our only issue is ballooning during the postcopy phase itself. Dave > Alex -- Dr. David Alan Gilbert / dgilbert@xxxxxxxxxx / Manchester, UK
