arm64: Honor limits set by bootloader

Introduce a varible to save bootloader enforced memory limits and
restricts adding beyond this boundary during a memory hotplug.

Change-Id: I28c100644b7287ec4625c4c018b5fffc865e2e72
Signed-off-by: Arun KS <arunks@codeaurora.org>

3 files changed, 35 insertions, 5 deletions

diff --git a/arch/arm64/mm/init.c b/arch/arm64/mm/init.c
index 75d363be3f36..7fd74d55c68e 100644
--- a/arch/arm64/mm/init.c
+++ b/arch/arm64/mm/init.c
@@ -152,6 +152,7 @@ static void __init arm64_memory_present(void)
 #endif
 
 static phys_addr_t memory_limit = (phys_addr_t)ULLONG_MAX;
+static phys_addr_t bootloader_memory_limit;
 
 /*
  * Limit the memory size that was specified via FDT.
@@ -205,6 +206,11 @@ void __init arm64_memblock_init(void)
 	 * via the linear mapping.
 	 */
 	if (memory_limit != (phys_addr_t)ULLONG_MAX) {
+		/*
+		 * Save bootloader imposed memory limit before we overwirte
+		 * memblock.
+		 */
+		bootloader_memory_limit = memblock_end_of_DRAM();
 		memblock_enforce_memory_limit(memory_limit);
 		memblock_add(__pa(_text), (u64)(_end - _text));
 	}
@@ -607,4 +613,25 @@ int arch_remove_memory(u64 start, u64 size)
 }
 
 #endif /* CONFIG_MEMORY_HOTREMOVE */
+static int arm64_online_page(struct page *page)
+{
+	unsigned long target_pfn = page_to_pfn(page);
+	unsigned long limit = __phys_to_pfn(bootloader_memory_limit);
+
+	if (target_pfn >= limit)
+		return -EINVAL;
+
+	__online_page_set_limits(page);
+	__online_page_increment_counters(page);
+	__online_page_free(page);
+
+	return 0;
+}
+
+static int __init arm64_memory_hotplug_init(void)
+{
+	set_online_page_callback(&arm64_online_page);
+	return 0;
+}
+subsys_initcall(arm64_memory_hotplug_init);
 #endif /* CONFIG_MEMORY_HOTPLUG */
diff --git a/include/linux/memory_hotplug.h b/include/linux/memory_hotplug.h
index 538488bd1d3d..ba23995e51b4 100644
--- a/include/linux/memory_hotplug.h
+++ b/include/linux/memory_hotplug.h
@@ -89,7 +89,7 @@ extern int test_pages_in_a_zone(unsigned long start_pfn, unsigned long end_pfn,
 	unsigned long *valid_start, unsigned long *valid_end);
 extern void __offline_isolated_pages(unsigned long, unsigned long);
 
-typedef void (*online_page_callback_t)(struct page *page);
+typedef int (*online_page_callback_t)(struct page *page);
 
 extern int set_online_page_callback(online_page_callback_t callback);
 extern int restore_online_page_callback(online_page_callback_t callback);
diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
index 2ad8a8888032..81957b076d66 100644
--- a/mm/memory_hotplug.c
+++ b/mm/memory_hotplug.c
@@ -45,7 +45,7 @@
  * and restore_online_page_callback() for generic callback restore.
  */
 
-static void generic_online_page(struct page *page);
+static int generic_online_page(struct page *page);
 
 static online_page_callback_t online_page_callback = generic_online_page;
 static DEFINE_MUTEX(online_page_callback_lock);
@@ -857,11 +857,12 @@ void __online_page_free(struct page *page)
 }
 EXPORT_SYMBOL_GPL(__online_page_free);
 
-static void generic_online_page(struct page *page)
+static int generic_online_page(struct page *page)
 {
 	__online_page_set_limits(page);
 	__online_page_increment_counters(page);
 	__online_page_free(page);
+	return 0;
 }
 
 static int online_pages_range(unsigned long start_pfn, unsigned long nr_pages,
@@ -870,11 +871,13 @@ static int online_pages_range(unsigned long start_pfn, unsigned long nr_pages,
 	unsigned long i;
 	unsigned long onlined_pages = *(unsigned long *)arg;
 	struct page *page;
+	int ret;
 	if (PageReserved(pfn_to_page(start_pfn)))
 		for (i = 0; i < nr_pages; i++) {
 			page = pfn_to_page(start_pfn + i);
-			(*online_page_callback)(page);
-			onlined_pages++;
+			ret = (*online_page_callback)(page);
+			if (!ret)
+				onlined_pages++;
 		}
 	*(unsigned long *)arg = onlined_pages;
 	return 0;