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

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Date:   Wed, 1 Jun 2022 09:28:05 +0000
From:   "Tian, Kevin" <kevin.tian@...el.com>
To:     Lu Baolu <baolu.lu@...ux.intel.com>,
        Joerg Roedel <joro@...tes.org>,
        "Raj, Ashok" <ashok.raj@...el.com>,
        Christoph Hellwig <hch@...radead.org>,
        "Jason Gunthorpe" <jgg@...dia.com>
CC:     Will Deacon <will@...nel.org>, Robin Murphy <robin.murphy@....com>,
        "Liu, Yi L" <yi.l.liu@...el.com>,
        "Pan, Jacob jun" <jacob.jun.pan@...el.com>,
        "iommu@...ts.linux-foundation.org" <iommu@...ts.linux-foundation.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH 09/12] iommu/vt-d: Check device list of domain in domain
 free path

> From: Lu Baolu <baolu.lu@...ux.intel.com>
> 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...