linux-kernel - [PATCH 3.2 153/200] powerpc/le: Ensure that the 'stop-self' RTAS token is handled correctly

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Date:	Mon, 31 Mar 2014 00:23:35 +0100
From:	Ben Hutchings <ben@...adent.org.uk>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:	akpm@...ux-foundation.org,
	"Benjamin Herrenschmidt" <benh@...nel.crashing.org>,
	"Tony Breeds" <tony@...eyournoodle.com>
Subject: [PATCH 3.2 153/200] powerpc/le: Ensure that the 'stop-self' RTAS
 token is handled correctly

3.2.56-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Tony Breeds <tony@...eyournoodle.com>

commit 41dd03a94c7d408d2ef32530545097f7d1befe5c upstream.

Currently we're storing a host endian RTAS token in
rtas_stop_self_args.token.  We then pass that directly to rtas.  This is
fine on big endian however on little endian the token is not what we
expect.

This will typically result in hitting:
	panic("Alas, I survived.\n");

To fix this we always use the stop-self token in host order and always
convert it to be32 before passing this to rtas.

Signed-off-by: Tony Breeds <tony@...eyournoodle.com>
Signed-off-by: Benjamin Herrenschmidt <benh@...nel.crashing.org>
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 arch/powerpc/platforms/pseries/hotplug-cpu.c | 22 +++++++++++-----------
 1 file changed, 11 insertions(+), 11 deletions(-)

--- a/arch/powerpc/platforms/pseries/hotplug-cpu.c
+++ b/arch/powerpc/platforms/pseries/hotplug-cpu.c
@@ -35,12 +35,7 @@
 #include "offline_states.h"
 
 /* This version can't take the spinlock, because it never returns */
-static struct rtas_args rtas_stop_self_args = {
-	.token = RTAS_UNKNOWN_SERVICE,
-	.nargs = 0,
-	.nret = 1,
-	.rets = &rtas_stop_self_args.args[0],
-};
+static int rtas_stop_self_token = RTAS_UNKNOWN_SERVICE;
 
 static DEFINE_PER_CPU(enum cpu_state_vals, preferred_offline_state) =
 							CPU_STATE_OFFLINE;
@@ -93,15 +88,20 @@ void set_default_offline_state(int cpu)
 
 static void rtas_stop_self(void)
 {
-	struct rtas_args *args = &rtas_stop_self_args;
+	struct rtas_args args = {
+		.token = cpu_to_be32(rtas_stop_self_token),
+		.nargs = 0,
+		.nret = 1,
+		.rets = &args.args[0],
+	};
 
 	local_irq_disable();
 
-	BUG_ON(args->token == RTAS_UNKNOWN_SERVICE);
+	BUG_ON(rtas_stop_self_token == RTAS_UNKNOWN_SERVICE);
 
 	printk("cpu %u (hwid %u) Ready to die...\n",
 	       smp_processor_id(), hard_smp_processor_id());
-	enter_rtas(__pa(args));
+	enter_rtas(__pa(&args));
 
 	panic("Alas, I survived.\n");
 }
@@ -384,10 +384,10 @@ static int __init pseries_cpu_hotplug_in
 		}
 	}
 
-	rtas_stop_self_args.token = rtas_token("stop-self");
+	rtas_stop_self_token = rtas_token("stop-self");
 	qcss_tok = rtas_token("query-cpu-stopped-state");
 
-	if (rtas_stop_self_args.token == RTAS_UNKNOWN_SERVICE ||
+	if (rtas_stop_self_token == RTAS_UNKNOWN_SERVICE ||
 			qcss_tok == RTAS_UNKNOWN_SERVICE) {
 		printk(KERN_INFO "CPU Hotplug not supported by firmware "
 				"- disabling.\n");

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