Re: [Qemu-devel] [PATCH v2 0/4] Balloon inhibit enhancements, vfio restriction

[Michael S. Tsirkin]

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?

I'd suggest making qemu_balloon_inhibit fail in that case,
and then vfio realize will fail as well.


> ---
> 
> Alex Williamson (4):
>       balloon: Allow nested inhibits
>       kvm: Use inhibit to prevent ballooning without synchronous mmu
>       vfio: Inhibit ballooning based on group attachment to a container
>       vfio/ccw/pci: Allow devices to opt-in for ballooning
> 
> 
>  accel/kvm/kvm-all.c           |    4 ++++
>  balloon.c                     |   13 ++++++++++---
>  hw/vfio/ccw.c                 |    9 +++++++++
>  hw/vfio/common.c              |   26 ++++++++++++++++++++++++++
>  hw/vfio/pci.c                 |   26 +++++++++++++++++++++++++-
>  hw/vfio/trace-events          |    1 +
>  hw/virtio/virtio-balloon.c    |    4 +---
>  include/hw/vfio/vfio-common.h |    2 ++
>  8 files changed, 78 insertions(+), 7 deletions(-)