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Subject[PATCH 3.16 136/136] kaiser: Set _PAGE_NX only if supported
3.16.54-rc1 review patch.  If anyone has any objections, please let me know.

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

From: Lepton Wu <ytht.net@gmail.com>

This finally resolve crash if loaded under qemu + haxm. Haitao Shan pointed
out that the reason of that crash is that NX bit get set for page tables.
It seems we missed checking if _PAGE_NX is supported in kaiser_add_user_map

Link: https://www.spinics.net/lists/kernel/msg2689835.html

Reviewed-by: Guenter Roeck <groeck@chromium.org>
Signed-off-by: Lepton Wu <ytht.net@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
(backported from Greg K-H's 4.4 stable-queue)
Signed-off-by: Juerg Haefliger <juerg.haefliger@canonical.com>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---
arch/x86/mm/kaiser.c | 2 ++
1 file changed, 2 insertions(+)

diff --git a/arch/x86/mm/kaiser.c b/arch/x86/mm/kaiser.c
index 2d5ac54dbcee..7cb57d14ddc0 100644
--- a/arch/x86/mm/kaiser.c
+++ b/arch/x86/mm/kaiser.c
@@ -195,6 +195,8 @@ static int kaiser_add_user_map(const void *__start_addr, unsigned long size,
* requires that not to be #defined to 0): so mask it off here.
*/
flags &= ~_PAGE_GLOBAL;
+ if (!(__supported_pte_mask & _PAGE_NX))
+ flags &= ~_PAGE_NX;

for (; address < end_addr; address += PAGE_SIZE) {
target_address = get_pa_from_mapping(address);
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