[PATCH 4.9 54/60] x86/CPU/AMD: Fix Zen SMT topology

From: Greg Kroah-Hartman
Date: Mon Feb 13 2017 - 08:17:16 EST

4.9-stable review patch. If anyone has any objections, please let me know.


From: Yazen Ghannam <Yazen.Ghannam@xxxxxxx>

commit 08b259631b5a1d912af4832847b5642f377d9101 upstream.


a33d331761bc ("x86/CPU/AMD: Fix Bulldozer topology")

our SMT scheduling topology for Fam17h systems is broken, because
the ThreadId is included in the ApicId when SMT is enabled.

So, without further decoding cpu_core_id is unique for each thread
rather than the same for threads on the same core. This didn't affect
systems with SMT disabled. Make cpu_core_id be what it is defined to be.

Signed-off-by: Yazen Ghannam <Yazen.Ghannam@xxxxxxx>
Signed-off-by: Borislav Petkov <bp@xxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Link: http://lkml.kernel.org/r/20170205105022.8705-2-bp@xxxxxxxxx
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

arch/x86/kernel/cpu/amd.c | 7 +++++++
1 file changed, 7 insertions(+)

--- a/arch/x86/kernel/cpu/amd.c
+++ b/arch/x86/kernel/cpu/amd.c
@@ -319,6 +319,13 @@ static void amd_get_topology(struct cpui
if (c->x86 == 0x15)
c->cu_id = ebx & 0xff;

+ if (c->x86 >= 0x17) {
+ c->cpu_core_id = ebx & 0xff;
+ if (smp_num_siblings > 1)
+ c->x86_max_cores /= smp_num_siblings;
+ }
* We may have multiple LLCs if L3 caches exist, so check if we
* have an L3 cache by looking at the L3 cache CPUID leaf.