[PATCH] x86: implement zone_dma32_size boot parameter

[KOSAKI Motohiro]

Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@xxxxxxxxxxxxxx>
---
 Documentation/kernel-parameters.txt |    5 +++++
 arch/x86/mm/init_64.c               |   17 ++++++++++++++++-
 2 files changed, 21 insertions(+), 1 deletions(-)

diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index a5966c0..25b4a53 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -2686,6 +2686,11 @@ and is between 256 and 4096 characters. It is defined in the file
 			Format:
 			<irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
 
+	zone_dma32_size=nn[KMG]		[KNL,BOOT,X86-64]
+			forces the dma32 zone to have an exact size of <nn>.
+			This works to reduce dma32 zone (In other word, to
+			increase normal zone) size.
+
 ______________________________________________________________________
 
 TODO:
diff --git a/arch/x86/mm/init_64.c b/arch/x86/mm/init_64.c
index 71a5929..12d813d 100644
--- a/arch/x86/mm/init_64.c
+++ b/arch/x86/mm/init_64.c
@@ -95,6 +95,21 @@ static int __init nonx32_setup(char *str)
 }
 __setup("noexec32=", nonx32_setup);
 
+static unsigned long max_dma32_pfn = MAX_DMA32_PFN;
+static int __init parse_zone_dma32_size(char *arg)
+{
+	unsigned long dma32_pages;
+
+	if (!arg)
+		return -EINVAL;
+
+	dma32_pages = memparse(arg, &arg) >> PAGE_SHIFT;
+	max_dma32_pfn = min(MAX_DMA_PFN + dma32_pages, MAX_DMA32_PFN);
+
+	return 0;
+}
+early_param("zone_dma32_size", parse_zone_dma32_size);
+
 /*
  * When memory was added/removed make sure all the processes MM have
  * suitable PGD entries in the local PGD level page.
@@ -625,7 +640,7 @@ void __init paging_init(void)
 
 	memset(max_zone_pfns, 0, sizeof(max_zone_pfns));
 	max_zone_pfns[ZONE_DMA] = MAX_DMA_PFN;
-	max_zone_pfns[ZONE_DMA32] = MAX_DMA32_PFN;
+	max_zone_pfns[ZONE_DMA32] = max_dma32_pfn;
 	max_zone_pfns[ZONE_NORMAL] = max_pfn;
 
 	sparse_memory_present_with_active_regions(MAX_NUMNODES);
-- 
1.6.5.2




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