Re: [Qemu-devel] [PATCH v3 0/4] Balloon inhibit enhancements, vfio restriction

[Michael S. Tsirkin]

On Tue, Aug 07, 2018 at 01:31:21PM -0600, Alex Williamson wrote:
> v3:
>  - Drop "nested" term in commit log (David)
>  - Adopt suggested wording in ccw code (Cornelia)
>  - Explain balloon inhibitor usage in vfio common (Peter)
>  - Fix to call inhibitor prior to re-using existing containers
>    to avoid gap that pinning may have occurred in set container
>    ioctl (self) - Peter, this change is the reason I didn't
>    include your R-b.
>  - Add R-b to patches 1 & 2
> 
> 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

One of the issues with pass-through is that it breaks overcommit
through swap. ballooning seems to offer one solution, instead of
making it work this patch just attempts to block ballooning.

I guess it's better than corrupting memory but I personally find this
approach disappointing.


> Alex Williamson (4):
>   balloon: Allow multiple inhibit users
>   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              | 51 +++++++++++++++++++++++++++++++++++
>  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, 103 insertions(+), 7 deletions(-)
> 
> -- 
> 2.18.0