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

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>

diff --git a/arch/powerpc/platforms/pseries/mobility.c b/arch/powerpc/platforms/pseries/mobility.c
index 88925f8..edc1ec4 100644 (file)
--- 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>
@@ -338,11 +339,19 @@ 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();