Re: [Intel-gfx] [PATCH v3 03/15] vfio: Accept vfio device file in the driver facing kAPI

[Jason Gunthorpe <jgg@nvidia.com>]

On Wed, Feb 15, 2023 at 10:19:35AM -0700, Alex Williamson wrote:
> On Wed, 15 Feb 2023 13:04:13 -0400
> Jason Gunthorpe <jgg@nvidia.com> wrote:
> 
> > On Wed, Feb 15, 2023 at 08:32:34AM -0700, Alex Williamson wrote:
> > 
> > > We've discussed this with Paolo before and I believe the bar of proof
> > > is not very high.  I suspect it's not a problem that the device itself
> > > is not yet accessible, so long as the user can prove they have the
> > > ability to access the device, such as access to a restricted file.  In
> > > most cases this isn't going to turn on wbinvd anyway since DMA will be
> > > coherent.  Thanks,  
> > 
> > Isn't that a second problem, we don't know if the device is coherent
> > until it is bound?
> 
> I think this is already accounted for in the conversion to device level
> IOMMU ops, ie. device_iommu_capable() follows the
> dev->iommu->iommu_dev->ops, where for example intel_iommu_capable() is
> only looking at the capabilities of the IOMMU managing the device.  We
> did some hand waving simplifications that was sufficient at some point,
> IIRC.  Thanks,

Oh right, I remember this now :)

Jason