On 2015/8/19 19:52, Robin Holt wrote:

On Sun, Aug 16, 2015 at 10:19 PM, Jiang Liu [off-list ref] wrote:

quoted

Function xpc_create_gru_mq_uv() allocates memory with __GFP_THISNODE
flag set, which may cause permanent memory allocation failure on
memoryless node. So replace cpu_to_node() with cpu_to_mem() to better
support memoryless node. For node with memory, cpu_to_mem() is the same
as cpu_to_node().

Signed-off-by: Jiang Liu <redacted>
---
 drivers/misc/sgi-xp/xpc_uv.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/misc/sgi-xp/xpc_uv.c b/drivers/misc/sgi-xp/xpc_uv.c
index 95c894482fdd..9210981c0d5b 100644
--- a/drivers/misc/sgi-xp/xpc_uv.c
+++ b/drivers/misc/sgi-xp/xpc_uv.c

@@ -238,7 +238,7 @@ xpc_create_gru_mq_uv(unsigned int mq_size, int cpu, char *irq_name,

        mq->mmr_blade = uv_cpu_to_blade_id(cpu);

-       nid = cpu_to_node(cpu);
+       nid = cpu_to_mem(cpu);

I would recommend rejecting this.  First, SGI's UV system does not and
can not support memory-less nodes.  Additionally the hardware _REALLY_
wants the memory to be local to the CPU.  We will register this memory
region with the node firmware.  That will set the hardware up to watch
this memory block and raise an IRQ targeting the registered CPU when
anything is written into the memory block.  This is all part of how
cross-partition communications expects to work.

Additionally, the interrupt handler will read the memory region, so
having node-local memory is extremely helpful.

Hi Robin,
	Thanks for review, I will drop this patch in next version.
Actually, if SGI UV systems don't support memoryless node, cpu_to_mem()
is the same as cpu_to_node().
Thanks!
Gerry

Thanks,
Robin

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