linux-kernel - [PATCH 5/6] powerpc: Implement DISCONTIGMEM and allow selection on PPC32

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Date:   Tue, 20 Feb 2018 17:14:23 +0100
From:   Jonathan Neuschäfer <j.neuschaefer@....net>
To:     linuxppc-dev@...ts.ozlabs.org
Cc:     linux-kernel@...r.kernel.org,
        Michael Ellerman <mpe@...erman.id.au>, linux-mm@...ck.org,
        Joel Stanley <joel@....id.au>,
        Jonathan Neuschäfer <j.neuschaefer@....net>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Philippe Ombredanne <pombredanne@...b.com>,
        Kate Stewart <kstewart@...uxfoundation.org>,
        Nathan Fontenot <nfont@...ux.vnet.ibm.com>,
        Michael Bringmann <mwb@...ux.vnet.ibm.com>,
        Thiago Jung Bauermann <bauerman@...ux.vnet.ibm.com>,
        Kees Cook <keescook@...omium.org>
Subject: [PATCH 5/6] powerpc: Implement DISCONTIGMEM and allow selection on PPC32

The implementation of pfn_to_nid and pfn_valid in mmzone.h is based on
arch/metag's implementation.

Signed-off-by: Jonathan Neuschäfer <j.neuschaefer@....net>
---

NOTE: Checking NODE_DATA(nid) in pfn_to_nid appears to be uncommon.
Running up to MAX_NUMNODES instead of checking NODE_DATA(nid) would
require the node_data array to be filled with valid pointers.
---
 arch/powerpc/Kconfig              |  5 ++++-
 arch/powerpc/include/asm/mmzone.h | 21 +++++++++++++++++++++
 arch/powerpc/mm/numa.c            |  7 +++++++
 3 files changed, 32 insertions(+), 1 deletion(-)

diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
index 73ce5dd07642..c2633b7b8ed9 100644
--- a/arch/powerpc/Kconfig
+++ b/arch/powerpc/Kconfig
@@ -639,7 +639,6 @@ config HAVE_MEMORYLESS_NODES
 
 config ARCH_SELECT_MEMORY_MODEL
 	def_bool y
-	depends on PPC64
 
 config ARCH_FLATMEM_ENABLE
 	def_bool y
@@ -654,6 +653,10 @@ config ARCH_SPARSEMEM_DEFAULT
 	def_bool y
 	depends on PPC_BOOK3S_64
 
+config ARCH_DISCONTIGMEM_ENABLE
+	def_bool y
+	depends on PPC32
+
 config SYS_SUPPORTS_HUGETLBFS
 	bool
 
diff --git a/arch/powerpc/include/asm/mmzone.h b/arch/powerpc/include/asm/mmzone.h
index 91c69ff53a8a..1684a5c98d23 100644
--- a/arch/powerpc/include/asm/mmzone.h
+++ b/arch/powerpc/include/asm/mmzone.h
@@ -26,6 +26,27 @@ extern struct pglist_data *node_data[];
  */
 #define NODE_DATA(nid)		(node_data[nid])
 
+static inline int pfn_to_nid(unsigned long pfn)
+{
+	int nid;
+
+	for (nid = 0; nid < MAX_NUMNODES && NODE_DATA(nid); nid++)
+		if (pfn >= node_start_pfn(nid) && pfn <= node_end_pfn(nid))
+			return nid;
+
+	return -1;
+}
+
+static inline int pfn_valid(int pfn)
+{
+	int nid = pfn_to_nid(pfn);
+
+	if (nid >= 0)
+		return pfn < node_end_pfn(nid);
+
+	return 0;
+}
+
 /*
  * Following are specific to this numa platform.
  */
diff --git a/arch/powerpc/mm/numa.c b/arch/powerpc/mm/numa.c
index dfe279529463..ec47f1081509 100644
--- a/arch/powerpc/mm/numa.c
+++ b/arch/powerpc/mm/numa.c
@@ -744,6 +744,13 @@ static void __init setup_nonnuma(void)
 				  PFN_PHYS(end_pfn - start_pfn),
 				  &memblock.memory, nid);
 		node_set_online(nid);
+
+		/*
+		 * On DISCONTIGMEM systems, place different memory blocks into
+		 * different nodes.
+		 */
+		if (IS_ENABLED(CONFIG_DISCONTIGMEM) && nid < MAX_NUMNODES - 1)
+			nid++;
 	}
 }
 
-- 
2.16.1