[PATCH 4.4 116/158] powerpc/pseries/mobility: prevent cpu hotplug during DT update

Greg Kroah-Hartman
2019-08-02T09:34:35Z

[ 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>
---
arch/powerpc/platforms/pseries/mobility.c | 9 +++++++++
1 file changed, 9 insertions(+)

diff --git a/arch/powerpc/platforms/pseries/mobility.c b/arch/powerpc/platforms/pseries/mobility.c
index c773396d0969..fcd1a32267c4 100644
--- a/arch/powerpc/platforms/pseries/mobility.c
+++ b/arch/powerpc/platforms/pseries/mobility.c
@@ -9,6 +9,7 @@
* 2 as published by the Free Software Foundation.
*/

+#include <linux/cpu.h>
#include <linux/kernel.h>
#include <linux/kobject.h>
#include <linux/smp.h>
@@ -309,11 +310,19 @@ 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();

--
2.20.1