Patch "x86/cpu/amd: Derive L3 shared_cpu_map from cpu_llc_shared_mask" has been added to the 4.13-stable tree

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

x86/cpu/amd: Derive L3 shared_cpu_map from cpu_llc_shared_mask

to the 4.13-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-derive-l3-shared_cpu_map-from-cpu_llc_shared_mask.patch
and it can be found in the queue-4.13 subdirectory.

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

From: Suravee Suthikulpanit <[email protected]>
Date: Mon, 31 Jul 2017 10:51:59 +0200
Subject: x86/cpu/amd: Derive L3 shared_cpu_map from cpu_llc_shared_mask

From: Suravee Suthikulpanit <[email protected]>

commit 2b83809a5e6d619a780876fcaf68cdc42b50d28c upstream.

For systems with X86_FEATURE_TOPOEXT, current logic uses the APIC ID to calculate shared_cpu_map. However, APIC IDs are not guaranteed to be contiguous for cores across different L3s (e.g. family17h system w/ downcore configuration). This breaks the logic, and results in an incorrect L3 shared_cpu_map.

Instead, always use the previously calculated cpu_llc_shared_mask of each CPU to derive the L3 shared_cpu_map.

---
 arch/x86/kernel/cpu/intel_cacheinfo.c |   32 ++++++++++++++++++--------------
 1 file changed, 18 insertions(+), 14 deletions(-)

@@ -811,7 +811,24 @@ static int __cache_amd_cpumap_setup(unsi
 	struct cacheinfo *this_leaf;
 	int i, sibling;
 
-	if (boot_cpu_has(X86_FEATURE_TOPOEXT)) {
+	/*
+	 * For L3, always use the pre-calculated cpu_llc_shared_mask
+	 * to derive shared_cpu_map.
+	 */
+	if (index == 3) {
+		for_each_cpu(i, cpu_llc_shared_mask(cpu)) {
+			this_cpu_ci = get_cpu_cacheinfo(i);
+			if (!this_cpu_ci->info_list)
+				continue;
+			this_leaf = this_cpu_ci->info_list + index;
+			for_each_cpu(sibling, cpu_llc_shared_mask(cpu)) {
+				if (!cpu_online(sibling))
+					continue;
+				cpumask_set_cpu(sibling,
+						&this_leaf->shared_cpu_map);
+			}
+		}
+	} else if (boot_cpu_has(X86_FEATURE_TOPOEXT)) {
 		unsigned int apicid, nshared, first, last;
 
 		this_leaf = this_cpu_ci->info_list + index;

@@ -837,19 +854,6 @@ static int __cache_amd_cpumap_setup(unsi
 					continue;
 				cpumask_set_cpu(sibling,
 						&this_leaf->shared_cpu_map);
-			}
-		}
-	} else if (index == 3) {
-		for_each_cpu(i, cpu_llc_shared_mask(cpu)) {
-			this_cpu_ci = get_cpu_cacheinfo(i);
-			if (!this_cpu_ci->info_list)
-				continue;
-			this_leaf = this_cpu_ci->info_list + index;
-			for_each_cpu(sibling, cpu_llc_shared_mask(cpu)) {
-				if (!cpu_online(sibling))
-					continue;
-				cpumask_set_cpu(sibling,
-						&this_leaf->shared_cpu_map);
 			}
 		}
 	} else

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

queue-4.13/x86-cpu-amd-derive-l3-shared_cpu_map-from-cpu_llc_shared_mask.patch