Re: [PATCH] vfio: fix deadlock between group lock and kvm lock

[Jason Gunthorpe]

On Tue, Jan 31, 2023 at 03:06:35PM -0500, Matthew Rosato wrote:
> @@ -799,13 +794,14 @@ EXPORT_SYMBOL_GPL(vfio_file_enforced_coherent);
>  void vfio_file_set_kvm(struct file *file, struct kvm *kvm)
>  {
>  	struct vfio_group *group = file->private_data;
> +	unsigned long flags;
>  
>  	if (!vfio_file_is_group(file))
>  		return;
>  
> -	mutex_lock(&group->group_lock);
> +	spin_lock_irqsave(&group->kvm_ref_lock, flags);
>  	group->kvm = kvm;
> -	mutex_unlock(&group->group_lock);
> +	spin_unlock_irqrestore(&group->kvm_ref_lock, flags);

We know we are in a sleeping context here so these are just
'spin_lock()', same with the other one

Otherwise it seems Ok to me

Reviewed-by: Jason Gunthorpe <jgg@xxxxxxxxxx>

Jason