smp_muxed_ipi_message_pass() invokes smp_ops->cause_ipi, which
updates the MFFR through an ioremapped address, to cause the
IPI. Because of this real mode callers cannot call
smp_muxed_ipi_message_pass() for IPI messaging.

This patch creates a separate function smp_muxed_ipi_set_message
just to set the IPI message without the cause_ipi routine.
After calling this function to set the IPI message, real
mode callers must cause the IPI directly.

As part of this, we also change smp_muxed_ipi_message_pass
to call smp_muxed_ipi_set_message to set the message instead
of doing it directly inside the routine.

Signed-off-by: Suresh Warrier <>
 arch/powerpc/include/asm/smp.h | 1 +
 arch/powerpc/kernel/smp.c      | 9 ++++++++-
 2 files changed, 9 insertions(+), 1 deletion(-)

diff --git a/arch/powerpc/include/asm/smp.h b/arch/powerpc/include/asm/smp.h
index 9ef9c37..78083ed 100644
--- a/arch/powerpc/include/asm/smp.h
+++ b/arch/powerpc/include/asm/smp.h
@@ -124,6 +124,7 @@ extern const char *smp_ipi_name[];
 /* for irq controllers with only a single ipi */
 extern void smp_muxed_ipi_set_data(int cpu, unsigned long data);
 extern void smp_muxed_ipi_message_pass(int cpu, int msg);
+extern void smp_muxed_ipi_set_message(int cpu, int msg);
 extern irqreturn_t smp_ipi_demux(void);
 void smp_init_pSeries(void);
diff --git a/arch/powerpc/kernel/smp.c b/arch/powerpc/kernel/smp.c
index a53a130..e222efc 100644
--- a/arch/powerpc/kernel/smp.c
+++ b/arch/powerpc/kernel/smp.c
@@ -218,7 +218,7 @@ void smp_muxed_ipi_set_data(int cpu, unsigned long data)
        info->data = data;
-void smp_muxed_ipi_message_pass(int cpu, int msg)
+void smp_muxed_ipi_set_message(int cpu, int msg)
        struct cpu_messages *info = &per_cpu(ipi_message, cpu);
        char *message = (char *)&info->messages;
@@ -228,6 +228,13 @@ void smp_muxed_ipi_message_pass(int cpu, int msg)
        message[msg] = 1;
+void smp_muxed_ipi_message_pass(int cpu, int msg)
+       struct cpu_messages *info = &per_cpu(ipi_message, cpu);
+       smp_muxed_ipi_set_message(cpu, msg);
         * cause_ipi functions are required to include a full barrier
         * before doing whatever causes the IPI.

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