linux-kernel - [PATCH 7/8 linux-next] mm: warn about possible alignment problem

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Date:   Fri,  2 Dec 2016 20:22:07 +0100
From:   Fabian Frederick <fabf@...net.be>
To:     Dan Williams <dan.j.williams@...el.com>
Cc:     linux-nvdimm@...ts.01.org, linux-kernel@...r.kernel.org,
        fabf@...net.be
Subject: [PATCH 7/8 linux-next] mm: warn about possible alignment problem

Commit 5f29a77cd957
("mm: fix mixed zone detection in devm_memremap_pages")
Aligned resource limits before region_intersects() which breaks
the following with false assertions on kernel command line: memmap=4M!700M

"devm_memremap_pages attempted on mixed region [ mem 0x2bc00000-0x2bfffff
flags 0x200]"

Memory regions
0x100000-0x2bbfffff: usable
0x2bc000000-0x2bbfffff: persistent
0x2c0000000-0x2bffffff: usable

resource start: 0x2bc00000
align start:    0x28000000
resource size:  0x3fffffff
align size:     0x80000000
SECTION_SIZE:    0x8000000

Now we need aligned memmap declarations based on 128M in this case
eg memmap=128!640M

Signed-off-by: Fabian Frederick <fabf@...net.be>
---
 kernel/memremap.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/kernel/memremap.c b/kernel/memremap.c
index b501e39..1bb5eec 100644
--- a/kernel/memremap.c
+++ b/kernel/memremap.c
@@ -296,8 +296,8 @@ void *devm_memremap_pages(struct device *dev, struct resource *res,
 		IORESOURCE_SYSTEM_RAM, IORES_DESC_NONE);
 
 	if (is_ram == REGION_MIXED) {
-		WARN_ONCE(1, "%s attempted on mixed region %pr\n",
-				__func__, res);
+		WARN_ONCE(1, "%s attempted on mixed region %pr or arguments not aligned to section size: %#lx\n",
+				__func__, res, SECTION_SIZE);
 		return ERR_PTR(-ENXIO);
 	}
 
-- 
2.7.4