linux-kernel - [PATCH 1/1] arm64: make section size configurable for memory hotplug

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Date:   Tue,  5 Jan 2021 17:28:46 -0800
From:   Sudarshan Rajagopalan <sudaraja@...eaurora.org>
To:     akpm@...ux-foundation.org, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Cc:     Sudarshan Rajagopalan <sudaraja@...eaurora.org>
Subject: [PATCH 1/1] arm64: make section size configurable for memory hotplug

Currently on arm64, memory section size is hard-coded to 1GB.
Make this configurable if memory-hotplug is enabled, to support
more finer granularity for hotplug-able memory.

Signed-off-by: Sudarshan Rajagopalan <sudaraja@...eaurora.org>
---
 arch/arm64/Kconfig                 | 11 +++++++++++
 arch/arm64/include/asm/sparsemem.h |  4 ++++
 2 files changed, 15 insertions(+)

diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index 6d232837cbee..34124eee65da 100644
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -294,6 +294,17 @@ config ARCH_ENABLE_MEMORY_HOTREMOVE
 config SMP
 	def_bool y
 
+config HOTPLUG_SIZE_BITS
+	int "Memory hotplug block size(29 => 512MB 30 => 1GB)"
+	depends on SPARSEMEM
+	depends on MEMORY_HOTPLUG
+	range 28 30
+	default 30
+	help
+	 Selects granularity of hotplug memory. Block size for
+	 memory hotplug is represent as a power of 2.
+	 If unsure, stick with default value.
+
 config KERNEL_MODE_NEON
 	def_bool y
 
diff --git a/arch/arm64/include/asm/sparsemem.h b/arch/arm64/include/asm/sparsemem.h
index 1f43fcc79738..3d5310f3aad5 100644
--- a/arch/arm64/include/asm/sparsemem.h
+++ b/arch/arm64/include/asm/sparsemem.h
@@ -7,7 +7,11 @@
 
 #ifdef CONFIG_SPARSEMEM
 #define MAX_PHYSMEM_BITS	CONFIG_ARM64_PA_BITS
+#ifndef CONFIG_MEMORY_HOTPLUG
 #define SECTION_SIZE_BITS	30
+#else
+#define SECTION_SIZE_BITS	CONFIG_HOTPLUG_SIZE_BITS
+#endif
 #endif
 
 #endif
-- 
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