Excerpts from Anatoly Pugachev's message of September 14, 2020 8:23 pm:

On Mon, Sep 14, 2020 at 10:00 AM Nicholas Piggin [off-list ref] wrote:

quoted

Excerpts from Nicholas Piggin's message of September 14, 2020 2:52 pm:

[...]

quoted

The basic fix for sparc64 is to remove its mm_cpumask clearing code. The
optimisation could be effectively restored by sending IPIs to mm_cpumask
members and having them remove themselves from mm_cpumask. This is more
tricky so I leave it as an exercise for someone with a sparc64 SMP.
powerpc has a (currently similarly broken) example.

So this compiles and boots on qemu, but qemu does not support any
sparc64 machines with SMP. Attempting some simple hacks doesn't get
me far because openbios isn't populating an SMP device tree, which
blows up everywhere.

The patch is _relatively_ simple, hopefully it shouldn't explode, so
it's probably ready for testing on real SMP hardware, if someone has
a few cycles.

Nick,

applied this patch to over 'v5.9-rc5' tag , used my test VM (ldom)
with 32 vcpus.
Machine boot, stress-ng test ( run as
"stress-ng --cpu 8 --io 8 --vm 8 --vm-bytes 2G --fork 8 --timeout 15m" )
finishes without errors.

Thank you very much Anatoly.

Thanks,
Nick