Patch "x86/CPU/AMD: Fix Zen SMT topology" has been added to the 4.9-stable tree

This is a note to let you know that I've just added the patch titled

x86/CPU/AMD: Fix Zen SMT topology

to the 4.9-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
x86-cpu-amd-fix-zen-smt-topology.patch
and it can be found in the queue-4.9 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Yazen Ghannam <[email protected]>
Date: Sun, 5 Feb 2017 11:50:22 +0100
Subject: x86/CPU/AMD: Fix Zen SMT topology

From: Yazen Ghannam <[email protected]>

commit 08b259631b5a1d912af4832847b5642f377d9101 upstream.

After:

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.

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

@@ -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.

Patches currently in stable-queue which might be from [email protected] are

queue-4.9/x86-cpu-amd-fix-zen-smt-topology.patch