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>
*/
void leave_mm(int cpu)
{
+ struct mm_struct *active_mm = percpu_read(cpu_tlbstate.active_mm);
if (percpu_read(cpu_tlbstate.state) == TLBSTATE_OK)
BUG();
- cpumask_clear_cpu(cpu,
- mm_cpumask(percpu_read(cpu_tlbstate.active_mm)));
- load_cr3(swapper_pg_dir);
+ if (cpumask_test_cpu(cpu, mm_cpumask(active_mm))) {
+ cpumask_clear_cpu(cpu, mm_cpumask(active_mm));
+ load_cr3(swapper_pg_dir);
+ }
}
EXPORT_SYMBOL_GPL(leave_mm);