From ce4e240c279a31096f74afa6584a62d64a1ba8c8 Mon Sep 17 00:00:00 2001 From: Suresh Siddha Date: Tue, 17 Mar 2009 10:16:54 -0800 Subject: [PATCH] x86: add x2apic_wrmsr_fence() to x2apic flush tlb paths Impact: optimize APIC IPI related barriers Uncached MMIO accesses for xapic are inherently serializing and hence we don't need explicit barriers for xapic IPI paths. x2apic MSR writes/reads don't have serializing semantics and hence need a serializing instruction or mfence, to make all the previous memory stores globally visisble before the x2apic msr write for IPI. Add x2apic_wrmsr_fence() in flush tlb path to x2apic specific paths. Signed-off-by: Suresh Siddha Cc: Peter Zijlstra Cc: Oleg Nesterov Cc: Jens Axboe Cc: Linus Torvalds Cc: "Paul E. McKenney" Cc: Rusty Russell Cc: Steven Rostedt Cc: "steiner@sgi.com" Cc: Nick Piggin LKML-Reference: <1237313814.27006.203.camel@localhost.localdomain> Signed-off-by: Ingo Molnar --- arch/x86/include/asm/apic.h | 10 ++++++++++ arch/x86/kernel/apic/x2apic_cluster.c | 6 ++++++ arch/x86/kernel/apic/x2apic_phys.c | 6 ++++++ arch/x86/mm/tlb.c | 5 ----- 4 files changed, 22 insertions(+), 5 deletions(-) diff --git a/arch/x86/include/asm/apic.h b/arch/x86/include/asm/apic.h index 6d5b6f0900e1..00f5962d82d0 100644 --- a/arch/x86/include/asm/apic.h +++ b/arch/x86/include/asm/apic.h @@ -108,6 +108,16 @@ extern void native_apic_icr_write(u32 low, u32 id); extern u64 native_apic_icr_read(void); #ifdef CONFIG_X86_X2APIC +/* + * Make previous memory operations globally visible before + * sending the IPI through x2apic wrmsr. We need a serializing instruction or + * mfence for this. + */ +static inline void x2apic_wrmsr_fence(void) +{ + asm volatile("mfence" : : : "memory"); +} + static inline void native_apic_msr_write(u32 reg, u32 v) { if (reg == APIC_DFR || reg == APIC_ID || reg == APIC_LDR || diff --git a/arch/x86/kernel/apic/x2apic_cluster.c b/arch/x86/kernel/apic/x2apic_cluster.c index 8fb87b6dd633..4a903e2f0d17 100644 --- a/arch/x86/kernel/apic/x2apic_cluster.c +++ b/arch/x86/kernel/apic/x2apic_cluster.c @@ -57,6 +57,8 @@ static void x2apic_send_IPI_mask(const struct cpumask *mask, int vector) unsigned long query_cpu; unsigned long flags; + x2apic_wrmsr_fence(); + local_irq_save(flags); for_each_cpu(query_cpu, mask) { __x2apic_send_IPI_dest( @@ -73,6 +75,8 @@ static void unsigned long query_cpu; unsigned long flags; + x2apic_wrmsr_fence(); + local_irq_save(flags); for_each_cpu(query_cpu, mask) { if (query_cpu == this_cpu) @@ -90,6 +94,8 @@ static void x2apic_send_IPI_allbutself(int vector) unsigned long query_cpu; unsigned long flags; + x2apic_wrmsr_fence(); + local_irq_save(flags); for_each_online_cpu(query_cpu) { if (query_cpu == this_cpu) diff --git a/arch/x86/kernel/apic/x2apic_phys.c b/arch/x86/kernel/apic/x2apic_phys.c index 23625b9f98b2..a284359627e7 100644 --- a/arch/x86/kernel/apic/x2apic_phys.c +++ b/arch/x86/kernel/apic/x2apic_phys.c @@ -58,6 +58,8 @@ static void x2apic_send_IPI_mask(const struct cpumask *mask, int vector) unsigned long query_cpu; unsigned long flags; + x2apic_wrmsr_fence(); + local_irq_save(flags); for_each_cpu(query_cpu, mask) { __x2apic_send_IPI_dest(per_cpu(x86_cpu_to_apicid, query_cpu), @@ -73,6 +75,8 @@ static void unsigned long query_cpu; unsigned long flags; + x2apic_wrmsr_fence(); + local_irq_save(flags); for_each_cpu(query_cpu, mask) { if (query_cpu != this_cpu) @@ -89,6 +93,8 @@ static void x2apic_send_IPI_allbutself(int vector) unsigned long query_cpu; unsigned long flags; + x2apic_wrmsr_fence(); + local_irq_save(flags); for_each_online_cpu(query_cpu) { if (query_cpu == this_cpu) diff --git a/arch/x86/mm/tlb.c b/arch/x86/mm/tlb.c index a654d59e4483..821e97017e95 100644 --- a/arch/x86/mm/tlb.c +++ b/arch/x86/mm/tlb.c @@ -186,11 +186,6 @@ static void flush_tlb_others_ipi(const struct cpumask *cpumask, cpumask_andnot(to_cpumask(f->flush_cpumask), cpumask, cpumask_of(smp_processor_id())); - /* - * Make the above memory operations globally visible before - * sending the IPI. - */ - smp_mb(); /* * We have to send the IPI only to * CPUs affected. -- 2.34.1