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Subject: Re: [RFC PATCH v4 01/13] iommu: Introduce dirty log tracking
 framework
To:     Lu Baolu <baolu.lu@linux.intel.com>,
        <linux-kernel@vger.kernel.org>,
        <linux-arm-kernel@lists.infradead.org>,
        <iommu@lists.linux-foundation.org>,
        Robin Murphy <robin.murphy@arm.com>,
        Will Deacon <will@kernel.org>,
        "Joerg Roedel" <joro@8bytes.org>,
        Jean-Philippe Brucker <jean-philippe@linaro.org>,
        Yi Sun <yi.y.sun@linux.intel.com>,
        Tian Kevin <kevin.tian@intel.com>
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CC:     Alex Williamson <alex.williamson@redhat.com>,
        Kirti Wankhede <kwankhede@nvidia.com>,
        Cornelia Huck <cohuck@redhat.com>,
        Jonathan Cameron <Jonathan.Cameron@huawei.com>,
        <wanghaibin.wang@huawei.com>, <jiangkunkun@huawei.com>,
        <yuzenghui@huawei.com>, <lushenming@huawei.com>
From:   Keqian Zhu <zhukeqian1@huawei.com>
Message-ID: <e38f1837-b814-3717-2faf-4df8349cb57c@huawei.com>
Date:   Wed, 12 May 2021 16:44:11 +0800
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On 2021/5/12 11:20, Lu Baolu wrote:
> On 5/11/21 3:40 PM, Keqian Zhu wrote:
>>> For upper layers, before starting page tracking, they check the
>>> dirty_page_trackable attribution of the domain and start it only it's
>>> capable. Once the page tracking is switched on the vendor iommu driver
>>> (or iommu core) should block further device attach/detach operations
>>> until page tracking is stopped.
>> But when a domain becomes capable after detaching a device, the upper layer
>> still needs to query it and enable dirty log for it...
>>
>> To make things coordinated, maybe the upper layer can register a notifier,
>> when the domain's capability change, the upper layer do not need to query, instead
>> they just need to realize a callback, and do their specific policy in the callback.
>> What do you think?
>>
> 
> That might be an option. But why not checking domain's attribution every
> time a new tracking period is about to start?
Hi Baolu,

I'll add an attribution in iommu_domain, and the vendor iommu driver will update
the attribution when attach/detach devices.

The attribute should be protected by a lock, so the upper layer shouldn't access
the attribute directly. Then the iommu_domain_support_dirty_log() still should be
retained. Does this design looks good to you?

Thanks,
Keqian