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>

diff --git a/arch/powerpc/platforms/pseries/setup.c b/arch/powerpc/platforms/pseries/setup.c
index 000724149089c032c45e375b30a0128e449d6e41..6c42cfde8415f31dacd0a981cee09535da581667 100644 (file)
--- 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);