linux-kernel - Re: [RFC v2] /dev/iommu uAPI proposal

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Date:   Thu, 15 Jul 2021 11:20:34 +0800
From:   Shenming Lu <lushenming@...wei.com>
To:     "Tian, Kevin" <kevin.tian@...el.com>
CC:     Jason Gunthorpe <jgg@...dia.com>,
        "Alex Williamson (alex.williamson@...hat.com)" 
        <alex.williamson@...hat.com>,
        "Jean-Philippe Brucker" <jean-philippe@...aro.org>,
        David Gibson <david@...son.dropbear.id.au>,
        Jason Wang <jasowang@...hat.com>,
        "parav@...lanox.com" <parav@...lanox.com>,
        "Enrico Weigelt, metux IT consult" <lkml@...ux.net>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Joerg Roedel <joro@...tes.org>,
        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>,
        "Kirti Wankhede" <kwankhede@...dia.com>,
        Robin Murphy <robin.murphy@....com>,
        "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
        "iommu@...ts.linux-foundation.org" <iommu@...ts.linux-foundation.org>,
        "David Woodhouse" <dwmw2@...radead.org>,
        LKML <linux-kernel@...r.kernel.org>,
        "Lu Baolu" <baolu.lu@...ux.intel.com>,
        "wanghaibin.wang@...wei.com" <wanghaibin.wang@...wei.com>
Subject: Re: [RFC v2] /dev/iommu uAPI proposal

On 2021/7/9 15:48, Tian, Kevin wrote:
> 4.6. I/O page fault
> +++++++++++++++++++
> 
> uAPI is TBD. Here is just about the high-level flow from host IOMMU driver
> to guest IOMMU driver and backwards. This flow assumes that I/O page faults
> are reported via IOMMU interrupts. Some devices report faults via device
> specific way instead of going through the IOMMU. That usage is not covered
> here:
> 
> -   Host IOMMU driver receives a I/O page fault with raw fault_data {rid, 
>     pasid, addr};
> 
> -   Host IOMMU driver identifies the faulting I/O page table according to
>     {rid, pasid} and calls the corresponding fault handler with an opaque
>     object (registered by the handler) and raw fault_data (rid, pasid, addr);
> 
> -   IOASID fault handler identifies the corresponding ioasid and device 
>     cookie according to the opaque object, generates an user fault_data 
>     (ioasid, cookie, addr) in the fault region, and triggers eventfd to 
>     userspace;
> 

Hi, I have some doubts here:

For mdev, it seems that the rid in the raw fault_data is the parent device's,
then in the vSVA scenario, how can we get to know the mdev(cookie) from the
rid and pasid?

And from this point of view，would it be better to register the mdev
(iommu_register_device()) with the parent device info?

Thanks,
Shenming