s390/vmcp: make use of contiguous memory allocator

If memory is fragmented it is unlikely that large order memory
allocations succeed. This has been an issue with the vmcp device
driver since a long time, since it requires large physical contiguous
memory ares for large responses.

To hopefully resolve this issue make use of the contiguous memory
allocator (cma). This patch adds a vmcp specific vmcp cma area with a
default size of 4MB. The size can be changed either via the
VMCP_CMA_SIZE config option at compile time or with the "vmcp_cma"
kernel parameter (e.g. "vmcp_cma=16m").

For any vmcp response buffers larger than 16k memory from the cma area
will be allocated. If such an allocation fails, there is a fallback to
the buddy allocator.

Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

1 files changed, 1 insertions, 0 deletions

diff --git a/arch/s390/kernel/setup.c b/arch/s390/kernel/setup.c
index a50238e17867..164a1e16b53e 100644
--- a/arch/s390/kernel/setup.c
+++ b/arch/s390/kernel/setup.c
@@ -925,6 +925,7 @@ void __init setup_arch(char **cmdline_p)
 	setup_memory_end();
 	setup_memory();
 	dma_contiguous_reserve(memory_end);
+	vmcp_cma_reserve();
 
 	check_initrd();
 	reserve_crashkernel();