x86, tlb: Switch cr3 in leave_mm() only when needed
Currently leave_mm() unconditionally switches the cr3 to swapper_pg_dir. But there is no need to change the cr3, if we already left that mm. intel_idle() for example calls leave_mm() on every deep c-state entry where the CPU flushes the TLB for us. Similarly flush_tlb_all() was also calling leave_mm() whenever the TLB is in LAZY state. Both these paths will be improved with this change. Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com> Link: http://lkml.kernel.org/r/1332460885.16101.147.camel@sbsiddha-desk.sc.intel.com Signed-off-by: H. Peter Anvin <hpa@zytor.com>
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@ -61,11 +61,13 @@ static DEFINE_PER_CPU_READ_MOSTLY(int, tlb_vector_offset);
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*/
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void leave_mm(int cpu)
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{
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struct mm_struct *active_mm = percpu_read(cpu_tlbstate.active_mm);
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if (percpu_read(cpu_tlbstate.state) == TLBSTATE_OK)
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BUG();
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cpumask_clear_cpu(cpu,
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mm_cpumask(percpu_read(cpu_tlbstate.active_mm)));
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if (cpumask_test_cpu(cpu, mm_cpumask(active_mm))) {
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cpumask_clear_cpu(cpu, mm_cpumask(active_mm));
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load_cr3(swapper_pg_dir);
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}
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}
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EXPORT_SYMBOL_GPL(leave_mm);
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