[tip:x86/cpu] x86/cache_info: Fix setup of l2/l3 ids

From: tip-bot for Shai Fultheim
Date: Tue May 08 2012 - 00:24:22 EST

Commit-ID: ddc5681ed33a279fdc188e98e71f0c539f08c6e6
Gitweb: http://git.kernel.org/tip/ddc5681ed33a279fdc188e98e71f0c539f08c6e6
Author: Shai Fultheim <shai@xxxxxxxxxxx>
AuthorDate: Fri, 20 Apr 2012 01:09:11 +0300
Committer: Ingo Molnar <mingo@xxxxxxxxxx>
CommitDate: Mon, 7 May 2012 15:27:37 +0200

x86/cache_info: Fix setup of l2/l3 ids

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@xxxxxxxxxxx>
[ rebased, simplified, and reworded the commit message]
Signed-off-by: Ido Yariv <ido@xxxxxxxxxx>
Cc: Borislav Petkov <borislav.petkov@xxxxxxx>
Cc: Andreas Herrmann <andreas.herrmann3@xxxxxxx>
Cc: Mike Travis <travis@xxxxxxx>
Cc: Dave Jones <davej@xxxxxxxxxx>
Link: http://lkml.kernel.org/r/1334873351-31142-1-git-send-email-ido@xxxxxxxxxx
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
arch/x86/kernel/cpu/intel_cacheinfo.c | 4 ++--
1 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kernel/cpu/intel_cacheinfo.c b/arch/x86/kernel/cpu/intel_cacheinfo.c
index b8f3653..9a7c90d 100644
--- a/arch/x86/kernel/cpu/intel_cacheinfo.c
+++ b/arch/x86/kernel/cpu/intel_cacheinfo.c
@@ -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);
case 3:
new_l3 = this_leaf.size/1024;
num_threads_sharing = 1 + this_leaf.eax.split.num_threads_sharing;
index_msb = get_count_order(
- l3_id = c->apicid >> index_msb;
+ l3_id = c->apicid & ~((1 << index_msb) - 1);
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/