On Mon, Nov 9, 2020 at 3:45 PM Tony Lindgren [off-list ref] wrote:

quoted

As discussed on IRC, I think it can still be done in one of these
ways, though admittedly none of them are perfect:

a) add runtime patching for __my_cpu_offset() when
  CONFIG_SMP_ON_UP is set. This adds complexity but avoids the
  fallback for for SMP&&CPU_V6. It possibly also speeds up
  running on single-cpu systems if the TPIDRPRW access adds
  any measurable runtime overhead compared to patching it out.

Out of these options a) sounds best to me.

Ok. Maninder, would you like to give implementing this a try?

quoted

b) If irq stacks are left as a compile-time option, that could be
  made conditional on "!(SMP&&CPU_V6)". Presumably very
  few people still run kernels built that way any more. The only
  supported platforms are i.MX3, OMAP2 and Realview-eb, all of
  which are fairly uncommon these days and would usually
  run v6-only non-SMP kernels.

This has been working just fine for years though. In general,
removing the conditional compile ifdefferey has made things quite
a bit easier for us, so let's continue on that.

quoted

c) If we decide that we no longer care about that configuration
  at all, we could decide to just make SMP depend on !CPU_V6,
  and possibly kill off the entire SMP_ON_UP patching logic.
  I suspect we still want to keep SMP_ON_UP for performance
  reasons, but I don't know how significant they are to start with.

And this too has been working just fine for years :)

I know it works, my point was that I'm not sure anyone cares
any more ;-)

I suppose the existence of omap2plus_defconfig and
imx_v6_v7_defconfig means it does at least get tested
regularly.

       Arnd

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