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

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Date:   Fri, 4 Jun 2021 09:30:37 +0800
From:   Jason Wang <jasowang@...hat.com>
To:     Jacob Pan <jacob.jun.pan@...ux.intel.com>,
        Shenming Lu <lushenming@...wei.com>
Cc:     Jason Gunthorpe <jgg@...dia.com>,
        Lu Baolu <baolu.lu@...ux.intel.com>,
        "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>, 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>,
        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


在 2021/6/4 上午2:19, Jacob Pan 写道:
> Hi Shenming,
>
> On Wed, 2 Jun 2021 12:50:26 +0800, Shenming Lu <lushenming@...wei.com>
> wrote:
>
>> 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?
>>
> I would think IOASID_BIND_PGTABLE is where fault handler should be
> registered. There wouldn't be any IO page fault without the binding anyway.
>
> I also don't understand why device drivers should register the fault
> handler, the fault is detected by the pIOMMU and injected to the vIOMMU. So
> I think it should be the IOASID itself register the handler.


As discussed in another thread.

I think the reason is that ATS doesn't forbid the #PF to be reported via 
a device specific way.

Thanks


>
>> Thanks,
>> Shenming
>>
>
> Thanks,
>
> Jacob
>