[PATCH v2] powerpc: align DTL buffer to AMS boundary

Nishanth Aravamudan nacc at us.ibm.com
Thu Apr 14 08:33:08 EST 2011

PAPR specifies that DTL buffers can not cross AMS environments (aka CMO
in the PAPR) and can not cross a memory entitlement granule boundary
(4k). This is found in section H_REGISTER_VPA of the PAPR.
kmalloc does not guarantee an alignment of the allocation, though,
beyond 8 bytes (at least in my understanding). Over-allocate and align
the resulting address. Tested both with and without AMS on a p7

Change from v1: removed extraneous #include.

Note, I initially put this in a firmware check if-block, but we have
also seen some issues with alignment with non-AMS partitions. The wasted
memory is unfortunate, though.

Cc: Paul Mackerras <paulus at samba.org>
Cc: Anton Blanchard <anton at samba.org>
Cc: linuxppc-dev at lists.ozlabs.org

 arch/powerpc/platforms/pseries/setup.c |    5 +++--
 1 files changed, 3 insertions(+), 2 deletions(-)

diff --git a/arch/powerpc/platforms/pseries/setup.c b/arch/powerpc/platforms/pseries/setup.c
index 0007241..a67be48 100644
--- a/arch/powerpc/platforms/pseries/setup.c
+++ b/arch/powerpc/platforms/pseries/setup.c
@@ -293,14 +293,15 @@ static int alloc_dispatch_logs(void)
 	for_each_possible_cpu(cpu) {
 		pp = &paca[cpu];
-		dtl = kmalloc_node(DISPATCH_LOG_BYTES, GFP_KERNEL,
-				   cpu_to_node(cpu));
+		dtl = kmalloc_node(DISPATCH_LOG_BYTES + DISPATCH_LOG_BYTES - 1,
+				   GFP_KERNEL, cpu_to_node(cpu));
 		if (!dtl) {
 			pr_warn("Failed to allocate dispatch trace log for cpu %d\n",
 			pr_warn("Stolen time statistics will be unreliable\n");
 		pp->dtl_ridx = 0;
 		pp->dispatch_log = dtl;

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