Re: [PATCH v5 04/14] driver core: platform: Add driver dma ownership management

From: Greg Kroah-Hartman
Date: Mon Feb 14 2022 - 08:37:24 EST


On Mon, Feb 14, 2022 at 09:18:53AM -0400, Jason Gunthorpe wrote:
> On Mon, Feb 14, 2022 at 10:59:50AM +0100, Greg Kroah-Hartman wrote:
>
> > > + if (ret && !drv->no_kernel_api_dma)
> > > + iommu_device_unuse_dma_api(dev);
> >
> > So you are now going to call this for every platform driver _unless_
> > they set this flag?
>
> Yes, it is necessary because VFIO supports platform devices as well
> and needs to ensure security. Conflicting kernel driver attachements
> must be blocked, just like for PCI.

A platform device shouldn't be using VFIO, but ugh, oh well, that ship
has sailed :(

And stop it with the "security" mess, do not give people a false sense
of it here please.

thanks,

greg k-h