powerpc/pseries: Use a kmem cache for DTL buffers

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 14.11.3.2 H_REGISTER_VPA of the PAPR.
kmalloc does not guarantee an alignment of the allocation, though,
beyond 8 bytes (at least in my understanding). Create a special kmem
cache for DTL buffers with the alignment requirement.

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

1 files changed, 10 insertions, 2 deletions

diff --git a/arch/powerpc/platforms/pseries/setup.c b/arch/powerpc/platforms/pseries/setup.c
index 000724149089..6c42cfde8415 100644
--- a/arch/powerpc/platforms/pseries/setup.c
+++ b/arch/powerpc/platforms/pseries/setup.c
@@ -287,14 +287,22 @@ static int alloc_dispatch_logs(void)
         int cpu, ret;
         struct paca_struct *pp;
         struct dtl_entry *dtl;
+        struct kmem_cache *dtl_cache;
 
         if (!firmware_has_feature(FW_FEATURE_SPLPAR))
                 return 0;
 
+        dtl_cache = kmem_cache_create("dtl", DISPATCH_LOG_BYTES,
+                                                DISPATCH_LOG_BYTES, 0, NULL);
+        if (!dtl_cache) {
+                pr_warn("Failed to create dispatch trace log buffer cache\n");
+                pr_warn("Stolen time statistics will be unreliable\n");
+                return 0;
+        }
+
         for_each_possible_cpu(cpu) {
                 pp = &paca[cpu];
-                dtl = kmalloc_node(DISPATCH_LOG_BYTES, GFP_KERNEL,
-                                   cpu_to_node(cpu));
+                dtl = kmem_cache_alloc(dtl_cache, GFP_KERNEL);
                 if (!dtl) {
                         pr_warn("Failed to allocate dispatch trace log for cpu %d\n",
                                 cpu);