From 01b0f0eae0812e80efeee4ee17687e5386335e08 Mon Sep 17 00:00:00 2001 From: Nicholas Piggin Date: Thu, 26 Nov 2020 20:25:30 +1000 Subject: powerpc/64s: Trim offlined CPUs from mm_cpumasks 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. A cast of many were involved in working this out, but in particular Milton, Aneesh, Paul made key discoveries. Fixes: 0cef77c7798a7 ("powerpc/64s/radix: flush remote CPUs out of single-threaded mm_cpumask") Signed-off-by: Nicholas Piggin Reviewed-by: Aneesh Kumar K.V Debugged-by: Milton Miller Debugged-by: Aneesh Kumar K.V Debugged-by: Paul Mackerras Signed-off-by: Michael Ellerman Link: https://lore.kernel.org/r/20201126102530.691335-5-npiggin@gmail.com --- arch/powerpc/include/asm/book3s/64/mmu.h | 12 ++++++++++++ arch/powerpc/mm/book3s64/mmu_context.c | 20 ++++++++++++++++++++ arch/powerpc/platforms/powermac/smp.c | 2 ++ arch/powerpc/platforms/powernv/smp.c | 3 +++ arch/powerpc/platforms/pseries/hotplug-cpu.c | 3 +++ 5 files changed, 40 insertions(+) diff --git a/arch/powerpc/include/asm/book3s/64/mmu.h b/arch/powerpc/include/asm/book3s/64/mmu.h index e0b52940e43c..750918451dd2 100644 --- a/arch/powerpc/include/asm/book3s/64/mmu.h +++ b/arch/powerpc/include/asm/book3s/64/mmu.h @@ -242,6 +242,18 @@ extern void radix_init_pseries(void); static inline void radix_init_pseries(void) { }; #endif +#ifdef CONFIG_HOTPLUG_CPU +#define arch_clear_mm_cpumask_cpu(cpu, mm) \ + do { \ + if (cpumask_test_cpu(cpu, mm_cpumask(mm))) { \ + atomic_dec(&(mm)->context.active_cpus); \ + cpumask_clear_cpu(cpu, mm_cpumask(mm)); \ + } \ + } while (0) + +void cleanup_cpu_mmu_context(void); +#endif + static inline int get_user_context(mm_context_t *ctx, unsigned long ea) { int index = ea >> MAX_EA_BITS_PER_CONTEXT; diff --git a/arch/powerpc/mm/book3s64/mmu_context.c b/arch/powerpc/mm/book3s64/mmu_context.c index 1c54821de7bf..0c8557220ae2 100644 --- a/arch/powerpc/mm/book3s64/mmu_context.c +++ b/arch/powerpc/mm/book3s64/mmu_context.c @@ -17,6 +17,7 @@ #include #include #include +#include #include #include @@ -307,3 +308,22 @@ void radix__switch_mmu_context(struct mm_struct *prev, struct mm_struct *next) isync(); } #endif + +/** + * cleanup_cpu_mmu_context - Clean up MMU details for this CPU (newly offlined) + * + * This clears the CPU from mm_cpumask for all processes, and then flushes the + * local TLB to ensure TLB coherency in case the CPU is onlined again. + * + * KVM guest translations are not necessarily flushed here. If KVM started + * using mm_cpumask or the Linux APIs which do, this would have to be resolved. + */ +#ifdef CONFIG_HOTPLUG_CPU +void cleanup_cpu_mmu_context(void) +{ + int cpu = smp_processor_id(); + + clear_tasks_mm_cpumask(cpu); + tlbiel_all(); +} +#endif diff --git a/arch/powerpc/platforms/powermac/smp.c b/arch/powerpc/platforms/powermac/smp.c index 74ebe664b016..adae2a6712e1 100644 --- 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(); + return 0; } diff --git a/arch/powerpc/platforms/powernv/smp.c b/arch/powerpc/platforms/powernv/smp.c index 54c4ba45c7ce..cbb67813cd5d 100644 --- a/arch/powerpc/platforms/powernv/smp.c +++ b/arch/powerpc/platforms/powernv/smp.c @@ -143,6 +143,9 @@ static int pnv_smp_cpu_disable(void) xive_smp_disable_cpu(); else xics_migrate_irqs_away(); + + cleanup_cpu_mmu_context(); + return 0; } diff --git a/arch/powerpc/platforms/pseries/hotplug-cpu.c b/arch/powerpc/platforms/pseries/hotplug-cpu.c index f2837e33bf5d..a02012f1b04a 100644 --- a/arch/powerpc/platforms/pseries/hotplug-cpu.c +++ b/arch/powerpc/platforms/pseries/hotplug-cpu.c @@ -90,6 +90,9 @@ static int pseries_cpu_disable(void) xive_smp_disable_cpu(); else xics_migrate_irqs_away(); + + cleanup_cpu_mmu_context(); + return 0; } -- cgit v1.2.3