Re: [PATCH 27/34] drm/i915/gvt: remove kvmgt_guest_{init,exit}

[Jason Gunthorpe]

On Mon, Apr 11, 2022 at 04:13:56PM +0200, Christoph Hellwig wrote:
> Merge these into their only callers.
> 
> Signed-off-by: Christoph Hellwig <hch@xxxxxx>
> ---
>  drivers/gpu/drm/i915/gvt/kvmgt.c | 129 ++++++++++++++-----------------
>  1 file changed, 60 insertions(+), 69 deletions(-)

It is nice

Reviewed-by: Jason Gunthorpe <jgg@xxxxxxxxxx>

> @@ -847,14 +873,37 @@ static int intel_vgpu_open_device(struct mdev_device *mdev)
>  		goto undo_group;
>  	}
>  
> -	ret = kvmgt_guest_init(mdev);
> -	if (ret)
> +	ret = -EEXIST;
> +	if (vgpu->attached)
> +		goto undo_group;
> +
> +	ret = -ESRCH;
> +	if (!vgpu->kvm || vgpu->kvm->mm != current->mm) {

For instance once all the obfuscation is stripped away it is easy to
see how the vgpu->kvm access here is unlocked against the notifier and
racy.

Jason