RE: [PATCH 09/12] iommu/vt-d: Check device list of domain in domain free path

[Tian, Kevin]

> From: Lu Baolu <baolu.lu@xxxxxxxxxxxxxxx>
> Sent: Friday, May 27, 2022 2:30 PM
> 
> When the IOMMU domain is about to be freed, it should not be set on any
> device. Instead of silently dealing with some bug cases, it's better to
> trigger a warning to report and fix any potential bugs at the first time.
> 


>  static void domain_exit(struct dmar_domain *domain)
>  {
> -
> -	/* Remove associated devices and clear attached or cached domains
> */
> -	domain_remove_dev_info(domain);
> +	if (WARN_ON(!list_empty(&domain->devices)))
> +		return;
> 

warning is good but it doesn't mean the driver shouldn't deal with
that situation to make it safer e.g. blocking DMA from all attached
device...