memory: merge modification of tao.zeng [5/9]

mm: check pfn overflow for low memory platform

PD#158373: mm: check pfn overflow for low memory platform

On ARM64 platform, when vmemmap_populate is called for reserve
memory for struct page, it reserved based 1GB a loop. And 16MB
memory will be reserved at least. This caused memory waste if
total RAM is less than 1GB.

Basically reserve memory size for struct page is calculated by:

    reserve size = sizeof(struct page) * number of pages.

For example, currently struct page is 64 bytes on ARM64. A page
is 4KB. So reserve size table can be:

    Memory  |  page count  |  reserve size(bytes)
-------------------------------------------------
     128MB  |       32768  |         2097152(2MB)
     256MB  |       65536  |         4194304(4MB)
     512MB  |      131072  |         8388608(8MB)

Note, This reserve is aligned at 2MB.

Change-Id: Ia7dbd250cc9aa37698071322f0ebc98bfcfb69db
Signed-off-by: tao zeng <tao.zeng@amlogic.com>
Signed-off-by: Jiamin Ma <jiamin.ma@amlogic.com>

1 files changed, 37 insertions, 0 deletions

diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
index 05615a3..eb8a729 100644
--- a/arch/arm64/mm/mmu.c
+++ b/arch/arm64/mm/mmu.c
@@ -30,6 +30,9 @@
 #include <linux/io.h>
 #include <linux/slab.h>
 #include <linux/stop_machine.h>
+#ifdef CONFIG_AMLOGIC_MODIFY
+#include <linux/bootmem.h>
+#endif /* CONFIG_AMLOGIC_MODIFY */
 
 #include <asm/barrier.h>
 #include <asm/cputype.h>
@@ -537,6 +540,25 @@ int __meminit vmemmap_populate(unsigned long start, unsigned long end, int node)
 	return vmemmap_populate_basepages(start, end, node);
 }
 #else	/* !ARM64_SWAPPER_USES_SECTION_MAPS */
+
+#ifdef CONFIG_AMLOGIC_MODIFY
+static int __init check_pfn_overflow(unsigned long pfn)
+{
+	unsigned long pfn_up;
+	unsigned long size;
+	/*
+	 * reserve pfn is larger than max_pfn, we don't need to reserve memory
+	 * this can help for memory less than 1GB platform
+	 */
+	size = sizeof(struct page);
+	pfn_up = ALIGN(max_pfn * size, PMD_SIZE);
+	pfn_up = (pfn_up + size - 1) / size;	/* round up */
+	if (pfn >= pfn_up)
+		return -ERANGE;
+	return 0;
+}
+#endif /* CONFIG_AMLOGIC_MODIFY */
+
 int __meminit vmemmap_populate(unsigned long start, unsigned long end, int node)
 {
 	unsigned long addr = start;
@@ -544,10 +566,20 @@ int __meminit vmemmap_populate(unsigned long start, unsigned long end, int node)
 	pgd_t *pgd;
 	pud_t *pud;
 	pmd_t *pmd;
+#ifdef CONFIG_AMLOGIC_MODIFY
+	struct page *page;
 
+	page = (struct page *)start;
+#endif /* CONFIG_AMLOGIC_MODIFY */
 	do {
 		next = pmd_addr_end(addr, end);
 
+	#ifdef CONFIG_AMLOGIC_MODIFY
+		/* page address may not just same as next */
+		while (((unsigned long)page) < next)
+			page++;
+	#endif /* CONFIG_AMLOGIC_MODIFY */
+
 		pgd = vmemmap_pgd_populate(addr, node);
 		if (!pgd)
 			return -ENOMEM;
@@ -567,6 +599,11 @@ int __meminit vmemmap_populate(unsigned long start, unsigned long end, int node)
 			set_pmd(pmd, __pmd(__pa(p) | PROT_SECT_NORMAL));
 		} else
 			vmemmap_verify((pte_t *)pmd, node, addr, next);
+
+	#ifdef CONFIG_AMLOGIC_MODIFY
+		if (check_pfn_overflow(page_to_pfn(page)))
+			break;
+	#endif /* CONFIG_AMLOGIC_MODIFY */
 	} while (addr = next, addr != end);
 
 	return 0;