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s390/mm,tlb: optimize TLB flushing for zEC12

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The zEC12 machines introduced the local-clearing control for the IDTE
and IPTE instruction. If the control is set only the TLB of the local
CPU is cleared of entries, either all entries of a single address space
for IDTE, or the entry for a single page-table entry for IPTE.
Without the local-clearing control the TLB flush is broadcasted to all
CPUs in the configuration, which is expensive.

The reset of the bit mask of the CPUs that need flushing after a
non-local IDTE is tricky. As TLB entries for an address space remain
in the TLB even if the address space is detached a new bit field is
required to keep track of attached CPUs vs. CPUs in the need of a
flush. After a non-local flush with IDTE the bit-field of attached CPUs
is copied to the bit-field of CPUs in need of a flush. The ordering
of operations on cpu_attach_mask, attach_count and mm_cpumask(mm) is
such that an underindication in mm_cpumask(mm) is prevented but an
overindication in mm_cpumask(mm) is possible.

Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
This commit is contained in:
Martin Schwidefsky
2014-04-03 13:55:01 +02:00
parent 02a8f3abb7
commit 1b948d6cae
11 changed files with 215 additions and 68 deletions
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6
arch/s390/kernel/smp.c
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@@ -236,6 +236,9 @@ static void pcpu_prepare_secondary(struct pcpu *pcpu, int cpu)
{
struct _lowcore *lc = pcpu->lowcore;
if (MACHINE_HAS_TLB_LC)
cpumask_set_cpu(cpu, &init_mm.context.cpu_attach_mask);
cpumask_set_cpu(cpu, mm_cpumask(&init_mm));
atomic_inc(&init_mm.context.attach_count);
lc->cpu_nr = cpu;
lc->percpu_offset = __per_cpu_offset[cpu];
@@ -760,6 +763,9 @@ void __cpu_die(unsigned int cpu)
cpu_relax();
pcpu_free_lowcore(pcpu);
atomic_dec(&init_mm.context.attach_count);
cpumask_clear_cpu(cpu, mm_cpumask(&init_mm));
if (MACHINE_HAS_TLB_LC)
cpumask_clear_cpu(cpu, &init_mm.context.cpu_attach_mask);
}
void __noreturn cpu_die(void)