[PATCH] powerpc/powernv: Return secondary CPUs to firmware on kexec

[Benjamin Herrenschmidt <benh@kernel.crashing.org>]

With OPAL v3 we can return secondary CPUs to firmware on kexec. This
allows firmware to do various cleanups making things generally more
reliable, and will enable the "new" kernel to call OPAL to perform
some reconfiguration tasks early on that can only be done while
all the CPUs are in firmware.

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

diff --git a/arch/powerpc/platforms/powernv/setup.c b/arch/powerpc/platforms/powernv/setup.c
index d4459bf..b59a1da 100644
--- a/arch/powerpc/platforms/powernv/setup.c
+++ b/arch/powerpc/platforms/powernv/setup.c
@@ -31,6 +31,7 @@
 #include <asm/xics.h>
 #include <asm/rtas.h>
 #include <asm/opal.h>
+#include <asm/kexec.h>
 
 #include "powernv.h"
 
@@ -143,6 +144,16 @@ static void pnv_shutdown(void)
 static void pnv_kexec_cpu_down(int crash_shutdown, int secondary)
 {
 	xics_kexec_teardown_cpu(secondary);
+
+	/* Return secondary CPUs to firmware on OPAL v3 */
+	if (firmware_has_feature(FW_FEATURE_OPALv3) && secondary) {
+		mb();
+		get_paca()->kexec_state = KEXEC_STATE_REAL_MODE;
+		mb();
+
+		/* Return the CPU to OPAL */
+		opal_return_cpu();
+	}
 }
 #endif /* CONFIG_KEXEC */