linux-kernel - Re: [PATCH v9 10/11] iommu: Per-domain I/O page fault handling

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Date:   Tue, 28 Jun 2022 20:18:16 +0800
From:   Baolu Lu <baolu.lu@...ux.intel.com>
To:     "Tian, Kevin" <kevin.tian@...el.com>,
        Jean-Philippe Brucker <jean-philippe@...aro.org>
Cc:     baolu.lu@...ux.intel.com, Joerg Roedel <joro@...tes.org>,
        Jason Gunthorpe <jgg@...dia.com>,
        Christoph Hellwig <hch@...radead.org>,
        "Raj, Ashok" <ashok.raj@...el.com>, Will Deacon <will@...nel.org>,
        Robin Murphy <robin.murphy@....com>,
        Jean-Philippe Brucker <jean-philippe@...aro.com>,
        "Jiang, Dave" <dave.jiang@...el.com>,
        Vinod Koul <vkoul@...nel.org>,
        Eric Auger <eric.auger@...hat.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>,
        "iommu@...ts.linux.dev" <iommu@...ts.linux.dev>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v9 10/11] iommu: Per-domain I/O page fault handling

On 2022/6/28 18:02, Tian, Kevin wrote:
>> From: Jean-Philippe Brucker <jean-philippe@...aro.org>
>> Sent: Tuesday, June 28, 2022 5:44 PM
>>
>> On Tue, Jun 28, 2022 at 08:39:36AM +0000, Tian, Kevin wrote:
>>>> From: Lu Baolu <baolu.lu@...ux.intel.com>
>>>> Sent: Tuesday, June 21, 2022 10:44 PM
>>>>
>>>> Tweak the I/O page fault handling framework to route the page faults to
>>>> the domain and call the page fault handler retrieved from the domain.
>>>> This makes the I/O page fault handling framework possible to serve more
>>>> usage scenarios as long as they have an IOMMU domain and install a
>> page
>>>> fault handler in it. Some unused functions are also removed to avoid
>>>> dead code.
>>>>
>>>> The iommu_get_domain_for_dev_pasid() which retrieves attached
>> domain
>>>> for a {device, PASID} pair is used. It will be used by the page fault
>>>> handling framework which knows {device, PASID} reported from the
>> iommu
>>>> driver. We have a guarantee that the SVA domain doesn't go away during
>>>> IOPF handling, because unbind() waits for pending faults with
>>>> iopf_queue_flush_dev() before freeing the domain. Hence, there's no
>> need
>>>> to synchronize life cycle of the iommu domains between the unbind() and
>>>> the interrupt threads.
>>>
>>> I found iopf_queue_flush_dev() is only called in intel-iommu driver. Did
>>> I overlook anything?
>>
>> The SMMU driver will need it as well when we upstream PRI support.
>> Currently it only supports stall, and that requires the device driver to
>> flush all DMA including stalled transactions *before* calling unbind(), so
>> ne need for iopf_queue_flush_dev() in this case.
>>
> 
> then it makes sense. Probably Baolu can add this information in the
> commit msg so others with similar question can quickly get the
> point here.

Sure. Updated.

Best regards,
baolu