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Subject: Re: [PATCH 7/7] iommu: Add iommu_domain::domain_ops
To:     "Tian, Kevin" <kevin.tian@intel.com>,
        Joerg Roedel <joro@8bytes.org>,
        Jason Gunthorpe <jgg@nvidia.com>,
        Christoph Hellwig <hch@infradead.org>,
        Ben Skeggs <bskeggs@redhat.com>,
        "Raj, Ashok" <ashok.raj@intel.com>, Will Deacon <will@kernel.org>,
        Robin Murphy <robin.murphy@arm.com>
References: <20220124071103.2097118-1-baolu.lu@linux.intel.com>
 <20220124071103.2097118-8-baolu.lu@linux.intel.com>
 <BN9PR11MB5276BE30652988271878E78C8C5E9@BN9PR11MB5276.namprd11.prod.outlook.com>
From:   Lu Baolu <baolu.lu@linux.intel.com>
Message-ID: <33060cd9-9115-013c-7253-52a36aa467e7@linux.intel.com>
Date:   Tue, 25 Jan 2022 12:59:14 +0800
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On 1/24/22 5:58 PM, Tian, Kevin wrote:
>> From: Lu Baolu <baolu.lu@linux.intel.com>
>> Sent: Monday, January 24, 2022 3:11 PM
>> +/**
>> + * struct domain_ops - per-domain ops
>> + * @attach_dev: attach an iommu domain to a device
>> + * @detach_dev: detach an iommu domain from a device
> 
> What is the criteria about whether an op should be iommu_ops or domain_ops
> when it requires both domain and device pointers like above two (and future
> PASID-based attach)?

Generally ops belong to iommu_ops if they are only device oriented, and
domain_ops if they are only domain oriented. But it's really hard to
judge when both device and domain are involved. Good question. :-)

Perhaps we should leave the attach/detach interfaces in iommu_ops since
they are related to device capabilities. For example, some devices
support attach_dev_pasid, while others not.

> 
> Other examples include:
> 	@apply_resv_region

This will be deprecated.

> 	@is_attach_deferred

Should be at least device centric (domain doesn't play any role here).
Further step is to save the is_attach_deferred at a flag in dev_iommu
and remove the ops (as Robin suggested).

> 
> Thanks
> Kevin
> 

Best regards,
baolu