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Re: [Qemu-devel] [PATCH v2 0/4] Balloon inhibit enhancements, vfio restr
From: |
Dr. David Alan Gilbert |
Subject: |
Re: [Qemu-devel] [PATCH v2 0/4] Balloon inhibit enhancements, vfio restriction |
Date: |
Tue, 31 Jul 2018 16:07:46 +0100 |
User-agent: |
Mutt/1.10.0 (2018-05-17) |
* Alex Williamson (address@hidden) wrote:
> On Tue, 31 Jul 2018 15:29:17 +0300
> "Michael S. Tsirkin" <address@hidden> 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 / address@hidden / Manchester, UK
- [Qemu-devel] [PATCH v2 0/4] Balloon inhibit enhancements, vfio restriction, Alex Williamson, 2018/07/30
- [Qemu-devel] [PATCH v2 1/4] balloon: Allow nested inhibits, Alex Williamson, 2018/07/30
- [Qemu-devel] [PATCH v2 2/4] kvm: Use inhibit to prevent ballooning without synchronous mmu, Alex Williamson, 2018/07/30
- [Qemu-devel] [PATCH v2 3/4] vfio: Inhibit ballooning based on group attachment to a container, Alex Williamson, 2018/07/30
- [Qemu-devel] [PATCH v2 4/4] vfio/ccw/pci: Allow devices to opt-in for ballooning, Alex Williamson, 2018/07/30
- Re: [Qemu-devel] [PATCH v2 0/4] Balloon inhibit enhancements, vfio restriction, Michael S. Tsirkin, 2018/07/31