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

[Peter Maydell]

On 9 March 2018 at 18:20, Guenter Roeck <address@hidden> 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.

thanks
-- PMM