netdev - Re: [net-next v2 1/1] virtual-bus: Implementation of Virtual Bus

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Message-ID: <fb73ceea-afc9-de6e-3a62-ac3bbc345fd2@redhat.com>
Date:   Thu, 21 Nov 2019 13:22:50 +0800
From:   Jason Wang <jasowang@...hat.com>
To:     Alex Williamson <alex.williamson@...hat.com>,
        Jason Gunthorpe <jgg@...pe.ca>
Cc:     "Michael S. Tsirkin" <mst@...hat.com>,
        Parav Pandit <parav@...lanox.com>,
        Jeff Kirsher <jeffrey.t.kirsher@...el.com>,
        davem@...emloft.net, gregkh@...uxfoundation.org,
        Dave Ertman <david.m.ertman@...el.com>, netdev@...r.kernel.org,
        linux-rdma@...r.kernel.org, nhorman@...hat.com,
        sassmann@...hat.com, Kiran Patil <kiran.patil@...el.com>,
        Tiwei Bie <tiwei.bie@...el.com>
Subject: Re: [net-next v2 1/1] virtual-bus: Implementation of Virtual Bus


On 2019/11/21 上午6:07, Alex Williamson wrote:
> On Wed, 20 Nov 2019 14:11:08 -0400
> Jason Gunthorpe<jgg@...pe.ca>  wrote:
>
>> On Wed, Nov 20, 2019 at 10:28:56AM -0700, Alex Williamson wrote:
>>>>> Are you objecting the mdev_set_iommu_deivce() stuffs here?
>>>> I'm questioning if it fits the vfio PCI device security model, yes.
>>> The mdev IOMMU backing device model is for when an mdev device has
>>> IOMMU based isolation, either via the PCI requester ID or via requester
>>> ID + PASID.  For example, an SR-IOV VF may be used by a vendor to
>>> provide IOMMU based translation and isolation, but the VF may not be
>>> complete otherwise to provide a self contained device.  It might
>>> require explicit coordination and interaction with the PF driver, ie.
>>> mediation.
>> In this case the PF does not look to be involved, the ICF kernel
>> driver is only manipulating registers in the same VF that the vfio
>> owns the IOMMU for.
> The mdev_set_iommu_device() call is probably getting caught up in the
> confusion of mdev as it exists today being vfio specific.  What I
> described in my reply is vfio specific.  The vfio iommu backend is
> currently the only code that calls mdev_get_iommu_device(), JasonW
> doesn't use it in the virtio-mdev code, so this seems like a stray vfio
> specific interface that's setup by IFC but never used.
>

It will be used by userspace driver through vhost-mdev code for having a 
correct IOMMU when doing DMA mappings.

Thanks