From: Nathan Lynch <nathanl@linux.ibm.com>
Date: Wed, 12 Jun 2019 04:45:05 +0000 (-0500)
Subject: powerpc/pseries/mobility: prevent cpu hotplug during DT update
X-Git-Tag: v5.2.5~153
X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=e26242e226785f6148689673ec281f89b0bf2931;p=thirdparty%2Fkernel%2Fstable.git

powerpc/pseries/mobility: prevent cpu hotplug during DT update

[ Upstream commit e59a175faa8df9d674247946f2a5a9c29c835725 ]

CPU online/offline code paths are sensitive to parts of the device
tree (various cpu node properties, cache nodes) that can be changed as
a result of a migration.

Prevent CPU hotplug while the device tree potentially is inconsistent.

Fixes: 410bccf97881 ("powerpc/pseries: Partition migration in the kernel")
Signed-off-by: Nathan Lynch <nathanl@linux.ibm.com>
Reviewed-by: Gautham R. Shenoy <ego@linux.vnet.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---

diff --git a/arch/powerpc/platforms/pseries/mobility.c b/arch/powerpc/platforms/pseries/mobility.c
index 0c48c89647837..50e7aee3c7f37 100644
--- a/arch/powerpc/platforms/pseries/mobility.c
+++ b/arch/powerpc/platforms/pseries/mobility.c
@@ -6,6 +6,7 @@
  * Copyright (C) 2010 IBM Corporation
  */
 
+#include <linux/cpu.h>
 #include <linux/kernel.h>
 #include <linux/kobject.h>
 #include <linux/smp.h>
@@ -335,11 +336,19 @@ void post_mobility_fixup(void)
 	if (rc)
 		printk(KERN_ERR "Post-mobility activate-fw failed: %d\n", rc);
 
+	/*
+	 * We don't want CPUs to go online/offline while the device
+	 * tree is being updated.
+	 */
+	cpus_read_lock();
+
 	rc = pseries_devicetree_update(MIGRATION_SCOPE);
 	if (rc)
 		printk(KERN_ERR "Post-mobility device tree update "
 			"failed: %d\n", rc);
 
+	cpus_read_unlock();
+
 	/* Possibly switch to a new RFI flush type */
 	pseries_setup_rfi_flush();