linux-kernel - Re: [RFC] /dev/ioasid uAPI proposal

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Date:   Wed, 2 Jun 2021 12:50:26 +0800
From:   Shenming Lu <lushenming@...wei.com>
To:     Jason Gunthorpe <jgg@...dia.com>,
        Lu Baolu <baolu.lu@...ux.intel.com>
CC:     "Tian, Kevin" <kevin.tian@...el.com>,
        LKML <linux-kernel@...r.kernel.org>,
        Joerg Roedel <joro@...tes.org>,
        David Woodhouse <dwmw2@...radead.org>,
        "iommu@...ts.linux-foundation.org" <iommu@...ts.linux-foundation.org>,
        "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
        "Alex Williamson (alex.williamson@...hat.com)" 
        <alex.williamson@...hat.com>, Jason Wang <jasowang@...hat.com>,
        Eric Auger <eric.auger@...hat.com>,
        Jonathan Corbet <corbet@....net>,
        "Raj, Ashok" <ashok.raj@...el.com>,
        "Liu, Yi L" <yi.l.liu@...el.com>, "Wu, Hao" <hao.wu@...el.com>,
        "Jiang, Dave" <dave.jiang@...el.com>,
        Jacob Pan <jacob.jun.pan@...ux.intel.com>,
        Jean-Philippe Brucker <jean-philippe@...aro.org>,
        David Gibson <david@...son.dropbear.id.au>,
        Kirti Wankhede <kwankhede@...dia.com>,
        "Robin Murphy" <robin.murphy@....com>,
        Zenghui Yu <yuzenghui@...wei.com>,
        "wanghaibin.wang@...wei.com" <wanghaibin.wang@...wei.com>
Subject: Re: [RFC] /dev/ioasid uAPI proposal

On 2021/6/2 1:33, Jason Gunthorpe wrote:
> On Tue, Jun 01, 2021 at 08:30:35PM +0800, Lu Baolu wrote:
> 
>> The drivers register per page table fault handlers to /dev/ioasid which
>> will then register itself to iommu core to listen and route the per-
>> device I/O page faults. 
> 
> I'm still confused why drivers need fault handlers at all?

Essentially it is the userspace that needs the fault handlers,
one case is to deliver the faults to the vIOMMU, and another
case is to enable IOPF on the GPA address space for on-demand
paging, it seems that both could be specified in/through the
IOASID_ALLOC ioctl?

Thanks,
Shenming