Re: [PATCH 2/2] powerpc/64s: Trim offlined CPUs from mm_cpumasks

[Nicholas Piggin]

Excerpts from Geert Uytterhoeven's message of December 10, 2020 7:06 pm:
> Hi Nicholas,
> 
> On Fri, Nov 20, 2020 at 4:01 AM Nicholas Piggin <npiggin@xxxxxxxxx> wrote:
>>
>> When offlining a CPU, powerpc/64s does not flush TLBs, rather it just
>> leaves the CPU set in mm_cpumasks, so it continues to receive TLBIEs
>> to manage its TLBs.
>>
>> However the exit_flush_lazy_tlbs() function expects that after
>> returning, all CPUs (except self) have flushed TLBs for that mm, in
>> which case TLBIEL can be used for this flush. This breaks for offline
>> CPUs because they don't get the IPI to flush their TLB. This can lead
>> to stale translations.
>>
>> Fix this by clearing the CPU from mm_cpumasks, then flushing all TLBs
>> before going offline.
>>
>> These offlined CPU bits stuck in the cpumask also prevents the cpumask
>> from being trimmed back to local mode, which means continual broadcast
>> IPIs or TLBIEs are needed for TLB flushing. This patch prevents that
>> situation too.
>>
>> Signed-off-by: Nicholas Piggin <npiggin@xxxxxxxxx>
> 
> Thanks for your patch!
> 
>> --- a/arch/powerpc/platforms/powermac/smp.c
>> +++ b/arch/powerpc/platforms/powermac/smp.c
>> @@ -911,6 +911,8 @@ static int smp_core99_cpu_disable(void)
>>
>>         mpic_cpu_set_priority(0xf);
>>
>> +       cleanup_cpu_mmu_context();
>> +
> 
> I guess this change broke pmac32_defconfig+SMP in v5.10-rc7?
> 
> arch/powerpc/platforms/powermac/smp.c: error: implicit
> declaration of function 'cleanup_cpu_mmu_context'
> [-Werror=implicit-function-declaration]:  => 914:2
> 
> http://kisskb.ellerman.id.au/kisskb/buildresult/14423174/

Hey, yeah it does thanks for catching it. This patch fixes it for me

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