linux-kernel - RE: [PATCH v4 07/10] iommu: Merge iommu_fault_event and iopf

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Date:   Wed, 30 Aug 2023 07:33:52 +0000
From:   "Tian, Kevin" <kevin.tian@...el.com>
To:     Baolu Lu <baolu.lu@...ux.intel.com>,
        Joerg Roedel <joro@...tes.org>,
        "Will Deacon" <will@...nel.org>,
        Robin Murphy <robin.murphy@....com>,
        "Jason Gunthorpe" <jgg@...pe.ca>,
        Jean-Philippe Brucker <jean-philippe@...aro.org>,
        Nicolin Chen <nicolinc@...dia.com>
CC:     "Liu, Yi L" <yi.l.liu@...el.com>,
        Jacob Pan <jacob.jun.pan@...ux.intel.com>,
        "iommu@...ts.linux.dev" <iommu@...ts.linux.dev>,
        "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH v4 07/10] iommu: Merge iommu_fault_event and iopf_fault

> From: Baolu Lu <baolu.lu@...ux.intel.com>
> Sent: Saturday, August 26, 2023 3:02 PM
> 
> On 8/25/23 4:03 PM, Tian, Kevin wrote:
> >> From: Lu Baolu <baolu.lu@...ux.intel.com>
> >> Sent: Friday, August 25, 2023 10:30 AM
> >>
> >> -/**
> >> - * struct iommu_fault_event - Generic fault event
> >> - *
> >> - * Can represent recoverable faults such as a page requests or
> >> - * unrecoverable faults such as DMA or IRQ remapping faults.
> >> - *
> >> - * @fault: fault descriptor
> >> - * @list: pending fault event list, used for tracking responses
> >> - */
> >> -struct iommu_fault_event {
> >> -	struct iommu_fault fault;
> >> -	struct list_head list;
> >> -};
> >> -
> >
> > iommu_fault_event is more forward-looking if unrecoverable fault
> > will be supported in future. From this angle it might make more
> > sense to keep it to replace iopf_fault.
> 
> Currently IOMMU drivers use
> 
> int report_iommu_fault(struct iommu_domain *domain, struct device *dev,
>                         unsigned long iova, int flags)
> 
> to report unrecoverable faults. There is no need for a generic fault
> event structure.
> 
> So alternatively, we can use iopf_fault for now and consolidate a
> generic fault data structure when there is a real need.
> 

Jean suggested to deprecate report_iommu_fault() and instead use
iommu_report_device_fault() for unrecoverable faults.

but not big deal if you prefer to iopf_fault for now.