linux-kernel - Re: [PATCH v1 09/10] iommu/vt-d: Refactor dmar_insert_one_dev

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Message-ID: <20220225140617.63a95344@jacob-builder>
Date:   Fri, 25 Feb 2022 14:09:37 -0800
From:   Jacob Pan <jacob.jun.pan@...ux.intel.com>
To:     Lu Baolu <baolu.lu@...ux.intel.com>
Cc:     Joerg Roedel <joro@...tes.org>, Kevin Tian <kevin.tian@...el.com>,
        Ashok Raj <ashok.raj@...el.com>, Liu Yi L <yi.l.liu@...el.com>,
        Robin Murphy <robin.murphy@....com>,
        Jason Gunthorpe <jgg@...dia.com>,
        Christoph Hellwig <hch@....de>,
        iommu@...ts.linux-foundation.org, linux-kernel@...r.kernel.org,
        jacob.jun.pan@...ux.intel.com
Subject: Re: [PATCH v1 09/10] iommu/vt-d: Refactor
 dmar_insert_one_dev_info()

Hi BaoLu,

On Mon,  7 Feb 2022 14:41:41 +0800, Lu Baolu <baolu.lu@...ux.intel.com>
wrote:

>  
> -	if (dev && domain_context_mapping(domain, dev)) {
> -		dev_err(dev, "Domain context map failed\n");
> -		dmar_remove_one_dev_info(dev);
> -		return NULL;
> -	}
> +	/* Setup the context entry for device: */
> +	ret = domain_context_mapping(domain, dev);
> +	if (ret)
> +		goto setup_context_err;
>  
> -	return domain;
> +	info->domain = domain;
> +	list_add_rcu(&info->link, &domain->devices);
> +
There seems to be an ordering problem. We need to do list_add_rcu()
*before*  domain_context_mapping(). Otherwise, while doing context mapping
the search for dev IOTLB support in iommu_support_dev_iotlb() will fail.
Then ATS capable device context will not have DTE bit set. The result is
DMAR unrecoverable fault while doing DMA.


Thanks,

Jacob