[PATCH 1/3] ARM: Premit ioremap() to map reserved pages

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euler inclusion
category: mm
target: upstream, 3.10, 3.4

----------------------------------------

This patch release the limitation set by commit 309caa9cc, which
prohibit ioremap() on all kernel managed pages.

Other architectures, such as x86 and powerpc (some specific platforms),
allow such mapping.

To allow ioremap() pages is an efficient way to avoid arm's mysterious
cache control. This feature will be used for arm kexec support to ensure
sure copied data goes into RAM even without cache flushing.

Cc: <stable@xxxxxxxxxxxxxxx> # 3.4+
Signed-off-by: Wang Nan <wangnan0@xxxxxxxxxx>

---
 arch/arm/mm/ioremap.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/arm/mm/ioremap.c b/arch/arm/mm/ioremap.c
index f123d6e..98b1c10 100644
--- a/arch/arm/mm/ioremap.c
+++ b/arch/arm/mm/ioremap.c
@@ -298,7 +298,7 @@ void __iomem * __arm_ioremap_pfn_caller(unsigned long pfn,
 	/*
 	 * Don't allow RAM to be mapped - this causes problems with ARMv6+
 	 */
-	if (WARN_ON(pfn_valid(pfn)))
+	if (WARN_ON(pfn_valid(pfn) && !PageReserved(pfn_to_page(pfn))))
 		return NULL;
 
 	area = get_vm_area_caller(size, VM_IOREMAP, caller);
-- 
1.8.4

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