[RFC PATCH v2 1/4] mm,memory_hotplug: Introduce MHP_MEMMAP_ON_MEMORY

From: Oscar Salvador <osalvador@suse.de>
To: david@redhat.com
Cc: mhocko@kernel.org, linux-kernel@vger.kernel.org,
	linux-mm@kvack.org, vbabka@suse.cz, pasha.tatashin@soleen.com,
	Oscar Salvador <osalvador@suse.de>
Subject: [RFC PATCH v2 1/4] mm,memory_hotplug: Introduce MHP_MEMMAP_ON_MEMORY
Date: Wed, 25 Nov 2020 12:20:45 +0100	[thread overview]
Message-ID: <20201125112048.8211-2-osalvador@suse.de> (raw)
In-Reply-To: <20201125112048.8211-1-osalvador@suse.de>

MHP_MEMMAP_ON_MEMORY tells the system that we want the memmap
pagetables to be built from the hot-added range.

Signed-off-by: Oscar Salvador <osalvador@suse.de>
---
 include/linux/memory_hotplug.h | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/include/linux/memory_hotplug.h b/include/linux/memory_hotplug.h
index 551093b74596..5b1ea1f8d1ab 100644
--- a/include/linux/memory_hotplug.h
+++ b/include/linux/memory_hotplug.h
@@ -70,6 +70,14 @@ typedef int __bitwise mhp_t;
  */
 #define MEMHP_MERGE_RESOURCE	((__force mhp_t)BIT(0))
 
+/*
+ * We want memmap (struct page array) to be self contained.
+ * To do so, we will use the beginning of the hot-added range to build
+ * the page tables for the memmap array that describes the entire range.
+ * Only selected architectures support it with SPARSE_VMEMMAP.
+ */
+#define MHP_MEMMAP_ON_MEMORY	((__force mhp_t)BIT(1))
+
 /*
  * Extended parameters for memory hotplug:
  * altmap: alternative allocator for memmap array (optional)
-- 
2.26.2

