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

From: Baolu Lu <baolu.lu@linux.intel.com>
To: "Tian, Kevin" <kevin.tian@intel.com>,
	Jean-Philippe Brucker <jean-philippe@linaro.org>
Cc: baolu.lu@linux.intel.com, Joerg Roedel <joro@8bytes.org>,
	Jason Gunthorpe <jgg@nvidia.com>,
	Christoph Hellwig <hch@infradead.org>,
	"Raj, Ashok" <ashok.raj@intel.com>, Will Deacon <will@kernel.org>,
	Robin Murphy <robin.murphy@arm.com>,
	Jean-Philippe Brucker <jean-philippe@linaro.com>,
	"Jiang, Dave" <dave.jiang@intel.com>,
	Vinod Koul <vkoul@kernel.org>, Eric Auger <eric.auger@redhat.com>,
	"Liu, Yi L" <yi.l.liu@intel.com>,
	"Pan, Jacob jun" <jacob.jun.pan@intel.com>,
	"iommu@lists.linux-foundation.org"
	<iommu@lists.linux-foundation.org>,
	"iommu@lists.linux.dev" <iommu@lists.linux.dev>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH v9 10/11] iommu: Per-domain I/O page fault handling
Date: Tue, 28 Jun 2022 20:18:16 +0800	[thread overview]
Message-ID: <826513b6-15d3-902d-03c2-7f7e68a84095@linux.intel.com> (raw)
In-Reply-To: <BN9PR11MB527605AA0663E8BE592898FE8CB89@BN9PR11MB5276.namprd11.prod.outlook.com>

On 2022/6/28 18:02, Tian, Kevin wrote:
>> From: Jean-Philippe Brucker <jean-philippe@linaro.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@linux.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