x86/cache_info: Fix setup of l2/l3 ids
Shai Fultheim [Thu, 19 Apr 2012 22:09:11 +0000 (01:09 +0300)]
On some architectures (such as vSMP), it is possible to have
CPUs with a different number of cores sharing the same cache.

The current implementation implicitly assumes that all CPUs will
have the same number of cores sharing caches, and as a result,
different CPUs can end up with the same l2/l3 ids.

Fix this by masking out the shared cache bits, instead of
shifting the APICID. By doing so, it is guaranteed that the
generated cache ids are always unique.

Signed-off-by: Shai Fultheim <shai@scalemp.com>
[ rebased, simplified, and reworded the commit message]
Signed-off-by: Ido Yariv <ido@wizery.com>
Cc: Borislav Petkov <borislav.petkov@amd.com>
Cc: Andreas Herrmann <andreas.herrmann3@amd.com>
Cc: Mike Travis <travis@sgi.com>
Cc: Dave Jones <davej@redhat.com>
Link: http://lkml.kernel.org/r/1334873351-31142-1-git-send-email-ido@wizery.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>

arch/x86/kernel/cpu/intel_cacheinfo.c

index b8f3653..9a7c90d 100644 (file)
@@ -615,14 +615,14 @@ unsigned int __cpuinit init_intel_cacheinfo(struct cpuinfo_x86 *c)
                                        new_l2 = this_leaf.size/1024;
                                        num_threads_sharing = 1 + this_leaf.eax.split.num_threads_sharing;
                                        index_msb = get_count_order(num_threads_sharing);
-                                       l2_id = c->apicid >> index_msb;
+                                       l2_id = c->apicid & ~((1 << index_msb) - 1);
                                        break;
                                case 3:
                                        new_l3 = this_leaf.size/1024;
                                        num_threads_sharing = 1 + this_leaf.eax.split.num_threads_sharing;
                                        index_msb = get_count_order(
                                                        num_threads_sharing);
-                                       l3_id = c->apicid >> index_msb;
+                                       l3_id = c->apicid & ~((1 << index_msb) - 1);
                                        break;
                                default:
                                        break;