[PATCH] powerpc/mm: Allow user space to map rtas_rmo_buf

[Vasant Hegde]

With commit 90a545e9 (restrict /dev/mem to idle io memory ranges) mapping
rtas_rmo_buf from user space is failing. Hence we are not able to make
RTAS syscall.

This patch calls page_is_rtas_user_buf before calling iomem_is_exclusive
in  devmem_is_allowed(). This will allow user space to map rtas_rmo_buf
and we are able to make RTAS syscall.

Reported-by: Bharata B Rao <bharata at linux.vnet.ibm.com>
CC: Dan Williams <dan.j.williams at intel.com>
CC: Nathan Fontenot <nfont at linux.vnet.ibm.com>
CC: Michael Ellerman <mpe at ellerman.id.au>
Signed-off-by: Vasant Hegde <hegdevasant at linux.vnet.ibm.com>
---
 arch/powerpc/mm/mem.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/powerpc/mm/mem.c b/arch/powerpc/mm/mem.c
index 22d94c3..d0f0a51 100644
--- a/arch/powerpc/mm/mem.c
+++ b/arch/powerpc/mm/mem.c
@@ -560,12 +560,12 @@ subsys_initcall(add_system_ram_resources);
  */
 int devmem_is_allowed(unsigned long pfn)
 {
+	if (page_is_rtas_user_buf(pfn))
+		return 1;
 	if (iomem_is_exclusive(PFN_PHYS(pfn)))
 		return 0;
 	if (!page_is_ram(pfn))
 		return 1;
-	if (page_is_rtas_user_buf(pfn))
-		return 1;
 	return 0;
 }
 #endif /* CONFIG_STRICT_DEVMEM */
-- 
2.1.0