linux-kernel - Re: [PATCH v3 00/11] iommu: Prepare to deliver page faults to user space

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Date:   Wed, 23 Aug 2023 09:24:03 +0800
From:   Baolu Lu <baolu.lu@...ux.intel.com>
To:     Jason Gunthorpe <jgg@...pe.ca>
Cc:     baolu.lu@...ux.intel.com, Joerg Roedel <joro@...tes.org>,
        Will Deacon <will@...nel.org>,
        Robin Murphy <robin.murphy@....com>,
        Kevin Tian <kevin.tian@...el.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>,
        iommu@...ts.linux.dev, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 00/11] iommu: Prepare to deliver page faults to user
 space

On 2023/8/22 2:31, Jason Gunthorpe wrote:
> On Fri, Aug 18, 2023 at 07:40:36AM +0800, Lu Baolu wrote:
>> When a user-managed page table is attached to an IOMMU, it is necessary
>> to deliver IO page faults to user space so that they can be handled
>> appropriately. One use case for this is nested translation, which is
>> currently being discussed in the mailing list.
>>
>> I have posted a RFC series [1] that describes the implementation of
>> delivering page faults to user space through IOMMUFD. This series has
>> received several comments on the IOMMU refactoring, which I am trying to
>> address in this series.
> 
> Looking at this after all the patches are applied..

Thank you very much for reviewing my patches.

> 
> iommu_report_device_fault() and iommu_queue_iopf() should be put in
> the same file.

Yes. I will move both into io-pgfault.c. After that, iommu_queue_iopf()
becomes static.

> 
> iommu_queue_iopf() seems misnamed since it isn't queuing anything. It
> is delivering the fault to the domain.

Yeah, perhaps we can rename it to iommu_handle_iopf().

/**
  * iommu_handle_iopf - IO Page Fault handler
  * @fault: fault event
  * @dev: struct device.

> 
> It is weird that iommu_sva_domain_alloc is not in the sva file

Agreed. I will move it to iommu-sva.c.

> iopf_queue_work() wrappers a work queue, but it should trampoline
> through another function before invoking the driver's callback and not
> invoke it with a weird work_struct - decode the group and get back the
> domain. Every single handler will require the group and domain.

The work queue wrapper is duplicate. I will remove it and let the driver
to call queue_work() directly.

> 
> Same for domain->iopf_handler, the domain should be an argument if we
> are invoking the function on a domain.
> 
> Perhaps group->domain is a simple answer.

Yes. I will add domain in fault group and make it part of the parameters
of the callback.

Best regards,
baolu