ARM: 7769/1: Cortex-A15: fix erratum 798181 implementation

Looking into the active_asids array is not enough, as we also need
to look into the reserved_asids array (they both represent processes
that are currently running).

Also, not holding the ASID allocator lock is racy, as another CPU
could schedule that process and trigger a rollover, making the erratum
workaround miss an IPI.

Exposing this outside of context.c is a little ugly on the side, so
let's define a new entry point that the erratum workaround can call
to obtain the cpumask.

Cc: <stable@vger.kernel.org> # 3.9
Acked-by: Will Deacon <will.deacon@arm.com>
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

1 files changed, 2 insertions, 16 deletions

diff --git a/arch/arm/kernel/smp_tlb.c b/arch/arm/kernel/smp_tlb.c
index 9a52a07aa40e..a98b62dca2fa 100644
--- a/arch/arm/kernel/smp_tlb.c
+++ b/arch/arm/kernel/smp_tlb.c
@@ -103,7 +103,7 @@ static void broadcast_tlb_a15_erratum(void)
 
 static void broadcast_tlb_mm_a15_erratum(struct mm_struct *mm)
 {
-        int cpu, this_cpu;
+        int this_cpu;
         cpumask_t mask = { CPU_BITS_NONE };
 
         if (!erratum_a15_798181())
@@ -111,21 +111,7 @@ static void broadcast_tlb_mm_a15_erratum(struct mm_struct *mm)
 
         dummy_flush_tlb_a15_erratum();
         this_cpu = get_cpu();
-        for_each_online_cpu(cpu) {
-                if (cpu == this_cpu)
-                        continue;
-                /*
-                 * We only need to send an IPI if the other CPUs are running
-                 * the same ASID as the one being invalidated. There is no
-                 * need for locking around the active_asids check since the
-                 * switch_mm() function has at least one dmb() (as required by
-                 * this workaround) in case a context switch happens on
-                 * another CPU after the condition below.
-                 */
-                if (atomic64_read(&mm->context.id) ==
-                    atomic64_read(&per_cpu(active_asids, cpu)))
-                        cpumask_set_cpu(cpu, &mask);
-        }
+        a15_erratum_get_cpumask(this_cpu, mm, &mask);
         smp_call_function_many(&mask, ipi_flush_tlb_a15_erratum, NULL, 1);
         put_cpu();
 }