linux-kernel - Re: [PATCH v3 2/8] iommu/sva: Use iopf domain attach/detach interface

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Date: Mon, 25 Mar 2024 11:52:05 +0800
From: Baolu Lu <baolu.lu@...ux.intel.com>
To: Jason Gunthorpe <jgg@...pe.ca>
Cc: baolu.lu@...ux.intel.com, Kevin Tian <kevin.tian@...el.com>,
 Joerg Roedel <joro@...tes.org>, Will Deacon <will@...nel.org>,
 Robin Murphy <robin.murphy@....com>,
 Jean-Philippe Brucker <jean-philippe@...aro.org>,
 Nicolin Chen <nicolinc@...dia.com>, Yi Liu <yi.l.liu@...el.com>,
 Jacob Pan <jacob.jun.pan@...ux.intel.com>,
 Joel Granados <j.granados@...sung.com>, iommu@...ts.linux.dev,
 virtualization@...ts.linux-foundation.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 2/8] iommu/sva: Use iopf domain attach/detach interface



On 3/23/24 12:59 AM, Jason Gunthorpe wrote:
> On Thu, Mar 14, 2024 at 03:41:23PM +0800, Baolu Lu wrote:
> 
>> The whole cookie mechanism aims to address two things:
>>
>> - Extend the domain lifetime until all pending page faults are
>> resolved.
> Like you answered, I think the flush is a simpler scheme..

Yeah! Let me head this direction.

> 
>> - Associate information about the iommu device with each attachment of
>>    the domain so that the iommufd device object ID could be quickly
>>    retrieved in the fault delivering path.
>   
>>> I see we also need to stick a pointer in the domain for iommufd to get
>>> back to the hwpt, but that doesn't seem to need such a big system to
>>> accomplish - just add a void *. It would make sense for the domain to
>>> have some optional pointer to a struct for all the fault related data
>>> that becomes allocated when a PRI domain is created..
>> It's not getting back hwpt from domain, just getting the iommufd_device
>> in the fault delivering path. The iommufd_device is not per-domain, but
>> per-domain-attachment.
> It does make sense you'd need that, but I think something like this is
> a more direct way to get it. Caller allocates the handle struct. The
> iopf will provide the handle from the XA to the
> callback. container_of() not void * is used to in the caller's API.

Your code looks attractive to me. It's much simpler. Thank you!

Best regards,
baolu