Hi Peter,
Thanks for your comments!
On Wed, Jan 9, 2019 at 5:03 PM Peter Maydell <peter.maydell@xxxxxxxxxx> wrote:
> On Wed, 9 Jan 2019 at 15:55, Auger Eric <eric.auger@xxxxxxxxxx> wrote:
> > On 1/3/19 10:42 AM, Geert Uytterhoeven wrote:
> > > Add a fallback for instantiating generic devices without a type-specific
> > > or compatible-specific instantiation method. This will be used when no
> > > other match is found.
> > >
> > > Generic device instantiation avoids having to write device-specific
> > > instantiation methods for each and every "simple" device using only a
> > > set of generic properties. Devices that need more specialized handling
> > > can still provide their own instantiation methods.
>
> > > + /* Ignoring the following may or may not work, hence the warning */
> > > + { "gpio-ranges", PROP_WARN }, /* no support for pinctrl yet */
> > > + { "dmas", PROP_WARN }, /* no support for external DMACs yet */
> > I would be tempted to simply reject things that may not work.
>
> More generally, this whole feature seems to be "allow things that
> might not work", isn't it? Otherwise we could just have explicit
I can remove the two PROP_WARN properties above from the list, if you prefer.
Exporting rcar-sata still works fine after that.
> whitelists for the devices we want to allow passthrough of and
> that we've tested to work.
In the end, this will become a loooooong list (SoC x devices)...
> I have to say I'm not really very enthusiastic about
> enhancing this to allow random device passthrough,
> because it encourages further use of this. If people
> want hardware that can be passed through they should
> put it behind a bus that can be probed and can go
> behind an IOMMU, ie pci or some equivalent. That
> is a supportable hardware mechanism. All this
> machinery feels very heath-robinson...
As no-iommu suppport is not upstream (in Qemu; it is upstream in Linux,
perhaps it should be removed?), all devices using DMA require being
behind an IOMMU.
Reality is that on embedded, on-SoC devices are usually not on a PCI bus.
But IOMMUs are present, and virtualization is wanted.
Thanks!
Gr{oetje,eeting}s,
Geert
--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@xxxxxxxxxxxxxx
In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
-- Linus Torvalds
