v4.19.13 snapshot.
diff --git a/arch/powerpc/kernel/dbell.c b/arch/powerpc/kernel/dbell.c
new file mode 100644
index 0000000..b6fe883
--- /dev/null
+++ b/arch/powerpc/kernel/dbell.c
@@ -0,0 +1,103 @@
+/*
+ * Author: Kumar Gala <galak@kernel.crashing.org>
+ *
+ * Copyright 2009 Freescale Semiconductor Inc.
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License as published by the
+ * Free Software Foundation; either version 2 of the License, or (at your
+ * option) any later version.
+ */
+
+#include <linux/stddef.h>
+#include <linux/kernel.h>
+#include <linux/smp.h>
+#include <linux/threads.h>
+#include <linux/hardirq.h>
+
+#include <asm/dbell.h>
+#include <asm/irq_regs.h>
+#include <asm/kvm_ppc.h>
+
+#ifdef CONFIG_SMP
+
+/*
+ * Doorbells must only be used if CPU_FTR_DBELL is available.
+ * msgsnd is used in HV, and msgsndp is used in !HV.
+ *
+ * These should be used by platform code that is aware of restrictions.
+ * Other arch code should use ->cause_ipi.
+ *
+ * doorbell_global_ipi() sends a dbell to any target CPU.
+ * Must be used only by architectures that address msgsnd target
+ * by PIR/get_hard_smp_processor_id.
+ */
+void doorbell_global_ipi(int cpu)
+{
+ u32 tag = get_hard_smp_processor_id(cpu);
+
+ kvmppc_set_host_ipi(cpu, 1);
+ /* Order previous accesses vs. msgsnd, which is treated as a store */
+ ppc_msgsnd_sync();
+ ppc_msgsnd(PPC_DBELL_MSGTYPE, 0, tag);
+}
+
+/*
+ * doorbell_core_ipi() sends a dbell to a target CPU in the same core.
+ * Must be used only by architectures that address msgsnd target
+ * by TIR/cpu_thread_in_core.
+ */
+void doorbell_core_ipi(int cpu)
+{
+ u32 tag = cpu_thread_in_core(cpu);
+
+ kvmppc_set_host_ipi(cpu, 1);
+ /* Order previous accesses vs. msgsnd, which is treated as a store */
+ ppc_msgsnd_sync();
+ ppc_msgsnd(PPC_DBELL_MSGTYPE, 0, tag);
+}
+
+/*
+ * Attempt to cause a core doorbell if destination is on the same core.
+ * Returns 1 on success, 0 on failure.
+ */
+int doorbell_try_core_ipi(int cpu)
+{
+ int this_cpu = get_cpu();
+ int ret = 0;
+
+ if (cpumask_test_cpu(cpu, cpu_sibling_mask(this_cpu))) {
+ doorbell_core_ipi(cpu);
+ ret = 1;
+ }
+
+ put_cpu();
+
+ return ret;
+}
+
+void doorbell_exception(struct pt_regs *regs)
+{
+ struct pt_regs *old_regs = set_irq_regs(regs);
+
+ irq_enter();
+
+ ppc_msgsync();
+
+ may_hard_irq_enable();
+
+ kvmppc_set_host_ipi(smp_processor_id(), 0);
+ __this_cpu_inc(irq_stat.doorbell_irqs);
+
+ smp_ipi_demux_relaxed(); /* already performed the barrier */
+
+ irq_exit();
+ set_irq_regs(old_regs);
+}
+#else /* CONFIG_SMP */
+void doorbell_exception(struct pt_regs *regs)
+{
+ printk(KERN_WARNING "Received doorbell on non-smp system\n");
+}
+#endif /* CONFIG_SMP */
+