Re: [Qemu-devel] [PATCH] fsl-imx6: Swap Ethernet interrupt defines

[Guenter Roeck <linux@roeck-us.net>]

On Fri, Mar 09, 2018 at 06:48:43PM +0000, Peter Maydell wrote:
> On 9 March 2018 at 18:20, Guenter Roeck <linux@roeck-us.net> wrote:
> > On Fri, Mar 09, 2018 at 05:47:16PM +0000, Peter Maydell wrote:
> >> Thanks for that really useful writeup. So if I understand correctly
> >> we have several choices here:
> >>
> >>  (1) we could implement a model of the IOMUX block that is at least
> >>  sufficient to support guests that configure it to route the ENET interrupt
> >>  line to a GPIO pin. Then we could apply this patch that fixes the ENET
> >>  line definitions. Old kernels would continue to work (for the same
> >>  reason they worked on hardware), and new ones would work now too.
> >>  This is in some ways the preferred option, but it's possibly a lot
> >>  of code and we're nearly in freeze for 2.12.
> >>
> >>  (2) we could leave everything as it is for 2.12. This would mean that
> >>  at least we don't regress setups that used to work on older QEMU versions.
> >>  Downside is that we wouldn't be able to run Linux v4.15+, or other
> >>  guest OSes that don't have the bug that older Linux kernels do.
> >>  (Presumably we'd only do this on the understanding that we were going
> >>  to go down route (1) for 2.13.)
> >>
> >>  (3) we could apply this patch for 2.12. Linux v4.15+ now works, as
> >>  do other guest OSes that use the ENET interrupt. v4.1 and older Linux
> >>  guests that used to boot in QEMU stop doing so, and 4.2-4.9 boot but
> >>  lose the ethernet device support. Perhaps for 2.13 we might
> >>  take route (1) to make those older guests start working again.
> >>
> >> Do I have that right?
> >>
> > Pretty much.
> >
> >> None of these options seems especially palatable to me, so we're
> >> choosing the lesser evil, I think... (unless somebody wants to say
> >> that option (1) would be 20 lines of code and here's the patch :-))
> >> I guess in the absence of (1) that (3) is better than (2) ?
> >>
> >
> > I would prefer (2). This is what I decided to use in my "local"
> > version of qemu. Older versions of Linux can be fixed by applying one
> > (4.2..4.9) or two (4.1 and older) upstream patches; anyone interested
> > running those kernels in qemu with Ethernet working should apply those
> > patches (or, alternatively, provide a patch adding IOMUX support to
> > qemu).
> 
> Did you mean "prefer (3) [apply this patch]" ? The rest of the paragraph
> makes more sense if you did.
> 
Yes, sorry.

Guenter