linux-kernel - Re: [PATCH v3 01/12] iommu: Introduce dirty log tracking framework

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Message-ID: <2c01425f-813c-4278-ba06-26d651496a5c@linux.intel.com>
Date:   Thu, 15 Apr 2021 18:21:22 +0800
From:   Lu Baolu <baolu.lu@...ux.intel.com>
To:     Keqian Zhu <zhukeqian1@...wei.com>, linux-kernel@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org,
        iommu@...ts.linux-foundation.org,
        Robin Murphy <robin.murphy@....com>,
        Will Deacon <will@...nel.org>, Joerg Roedel <joro@...tes.org>,
        Yi Sun <yi.y.sun@...ux.intel.com>,
        Jean-Philippe Brucker <jean-philippe@...aro.org>,
        Jonathan Cameron <Jonathan.Cameron@...wei.com>,
        Tian Kevin <kevin.tian@...el.com>
Cc:     baolu.lu@...ux.intel.com,
        Alex Williamson <alex.williamson@...hat.com>,
        Cornelia Huck <cohuck@...hat.com>,
        Kirti Wankhede <kwankhede@...dia.com>,
        wanghaibin.wang@...wei.com, jiangkunkun@...wei.com,
        yuzenghui@...wei.com, lushenming@...wei.com
Subject: Re: [PATCH v3 01/12] iommu: Introduce dirty log tracking framework

Hi,

On 2021/4/15 15:43, Keqian Zhu wrote:
>>> design it as not switchable. I will modify the commit message of patch#12, thanks!
>> I am not sure that I fully get your point. But I can't see any gaps of
>> using iommu_dev_enable/disable_feature() to switch dirty log on and off.
>> Probably I missed anything.
> IOMMU_DEV_FEAT_HWDBM just tells user whether underlying IOMMU driver supports
> dirty tracking, it is not used to management the status of dirty log tracking.
> 
> The feature reporting is per device, but the status management is per iommu_domain.
> Only when all devices in a domain support HWDBM, we can start dirty log for the domain.

So why not

	for_each_device_attached_domain()
		iommu_dev_enable_feature(IOMMU_DEV_FEAT_HWDBM)

?
> 
> And I think we'd better not mix the feature reporting and status management. Thoughts?
> 

I am worrying about having two sets of APIs for single purpose. From
vendor iommu driver's point of view, this feature is per device. Hence,
it still needs to do the same thing.

Best regards,
baolu