Re: [Devel] [PATCH hci-8.1 v3 0/1] vfio: kvm reference leak on live update

[Konstantin Khorenko <khorenko@virtuozzo.com>]

Applying with these fixes on my side:
- commit message: KVMGT reads device->kvm while the guest runs too,
  not only in open_device() and at close;
- struct vfio_device comment: the flag is for a driver that uses
  device->kvm while the device is open, not only in open_device();
- the comments before the kvm get in vfio_df_group_open() and
  vfio_df_ioctl_bind_iommufd(): the pointer is saved only when the
  driver set needs_kvm_ref.

On Thu, 5 Nov 2026 16:17:58 +0200, Andrey Drobyshev wrote:
> Andrey Drobyshev (1):
>   vfio: take the kvm reference only for drivers that read device->kvm

Thanks, the code is right, and the test with this patch alone answers
the patch 2 question.

The first two fixes undo a mistake of mine: item 1 of my v2 reply said
"in open_device(), not after it". That holds for vfio_ap and zdev, but
KVMGT also calls kvm_write_track_add_gfn() on device->kvm while the
guest runs. Details are in the reply to the patch.

For the mainline version (VSTOR-153437): all three drivers already
take their own reference on the kvm in open_device(). So upstream may
prefer the core to hold its reference only across open_device() and
drop it right after, with no flag at all. Worth raising there.

-- 
Konstantin Khorenko,
Virtuozzo Linux Kernel Team

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