[PATCH v3 4/5] powerpc/xive: defer setting cause_ipi until IPI init succeeds

xive_smp_probe() currently assigns smp_ops->cause_ipi = xive_cause_ipi
before calling xive_init_ipis() and xive_setup_cpu_ipi().  If either
call fails, the platform probe handler returns early but cause_ipi
remains pointing to xive_cause_ipi -- which accesses per-cpu IPI data
(xc->ipi_data) that was never properly initialized, leading to
a WARN and a crash.

Move the cause_ipi assignment to after both calls succeed, so that
smp_ops->cause_ipi is only set when the IPI subsystem is fully
initialized.

Signed-off-by: Gou Hao <[email protected]>
Suggested-by: Cédric Le Goater <[email protected]>
Reviewed-by: jiazhenyuan <[email protected]>
---
 arch/powerpc/sysdev/xive/common.c | 10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

diff --git a/arch/powerpc/sysdev/xive/common.c b/arch/powerpc/sysdev/xive/common.c
index bbe7c85274ea..8ae088632337 100644
--- a/arch/powerpc/sysdev/xive/common.c
+++ b/arch/powerpc/sysdev/xive/common.c
@@ -1269,15 +1269,19 @@ int __init xive_smp_probe(void)
 {
 	int ret;
 
-	smp_ops->cause_ipi = xive_cause_ipi;
-
 	/* Register the IPI */
 	ret = xive_init_ipis();
 	if (ret < 0)
 		return ret;
 
 	/* Allocate and setup IPI for the boot CPU */
-	return xive_setup_cpu_ipi(smp_processor_id());
+	ret = xive_setup_cpu_ipi(smp_processor_id());
+	if (ret < 0)
+		return ret;
+
+	smp_ops->cause_ipi = xive_cause_ipi;
+
+	return 0;
 }
 
 #endif /* CONFIG_SMP */
-- 
2.20.1