[PATCH 1/3] powerpc/cacheinfo: add cacheinfo_teardown, cacheinfo_rebuild

[Nathan Lynch]

Allow external callers to force the cacheinfo code to release all its
references to cache nodes, e.g. before processing device tree updates
post-migration, and to rebuild the hierarchy afterward.

CPU online/offline must be blocked by callers; enforce this.

Fixes: 410bccf97881 ("powerpc/pseries: Partition migration in the kernel")
Signed-off-by: Nathan Lynch <nathanl at linux.ibm.com>
---
 arch/powerpc/kernel/cacheinfo.c | 21 +++++++++++++++++++++
 arch/powerpc/kernel/cacheinfo.h |  4 ++++
 2 files changed, 25 insertions(+)

diff --git a/arch/powerpc/kernel/cacheinfo.c b/arch/powerpc/kernel/cacheinfo.c
index 862e2890bd3d..42c559efe060 100644
--- a/arch/powerpc/kernel/cacheinfo.c
+++ b/arch/powerpc/kernel/cacheinfo.c
@@ -896,4 +896,25 @@ void cacheinfo_cpu_offline(unsigned int cpu_id)
 	if (cache)
 		cache_cpu_clear(cache, cpu_id);
 }
+
+void cacheinfo_teardown(void)
+{
+	unsigned int cpu;
+
+	lockdep_assert_cpus_held();
+
+	for_each_online_cpu(cpu)
+		cacheinfo_cpu_offline(cpu);
+}
+
+void cacheinfo_rebuild(void)
+{
+	unsigned int cpu;
+
+	lockdep_assert_cpus_held();
+
+	for_each_online_cpu(cpu)
+		cacheinfo_cpu_online(cpu);
+}
+
 #endif /* (CONFIG_PPC_PSERIES && CONFIG_SUSPEND) || CONFIG_HOTPLUG_CPU */
diff --git a/arch/powerpc/kernel/cacheinfo.h b/arch/powerpc/kernel/cacheinfo.h
index 955f5e999f1b..52bd3fc6642d 100644
--- a/arch/powerpc/kernel/cacheinfo.h
+++ b/arch/powerpc/kernel/cacheinfo.h
@@ -6,4 +6,8 @@
 extern void cacheinfo_cpu_online(unsigned int cpu_id);
 extern void cacheinfo_cpu_offline(unsigned int cpu_id);
 
+/* Allow migration/suspend to tear down and rebuild the hierarchy. */
+extern void cacheinfo_teardown(void);
+extern void cacheinfo_rebuild(void);
+
 #endif /* _PPC_CACHEINFO_H */
-- 
2.20.1