Messages in this thread | | | From | Michael Ellerman <> | Subject | Re: [PATCH 2/2] powerpc/64s: Trim offlined CPUs from mm_cpumasks | Date | Tue, 15 Dec 2020 21:33:15 +1100 |
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Nicholas Piggin <npiggin@gmail.com> writes: > Excerpts from Michael Ellerman's message of December 14, 2020 8:43 pm: >> Nicholas Piggin <npiggin@gmail.com> writes: >>> 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@gmail.com> 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@gmail.com> >>>> >>>> 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 >>> >>> --- >>> From a9b5ec92ffac975e81c6d7db6ff2b1486b2723f7 Mon Sep 17 00:00:00 2001 >>> From: Nicholas Piggin <npiggin@gmail.com> >>> Date: Mon, 14 Dec 2020 13:52:39 +1000 >>> Subject: [PATCH] powerpc/32s: Fix cleanup_cpu_mmu_context() compile bug >>> >>> 32s has no tlbiel_all() defined, so just disable the cleanup with a >>> comment. >> >> Or what about just: > > That works, I kind of wanted it in there explicit that we don't > clean up on 32s. I don't mind if you prefer this though.
OK. I'll merge my version because I can do that without needing to merge master in order to get the broken commit into my tree.
cheers
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