[PATCH 2/2] x86/amd: Derive L3 shared_cpu_map from cpu_llc_shared_mask

[Borislav Petkov]

From: Suravee Suthikulpanit <suravee.suthikulpanit@xxxxxxx>

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.

Signed-off-by: Suravee Suthikulpanit <suravee.suthikulpanit@xxxxxxx>
Cc: x86-ml <x86@xxxxxxxxxx>
Link: http://lkml.kernel.org/r/1501206755-2396-1-git-send-email-suravee.suthikulpanit@xxxxxxx
Signed-off-by: Borislav Petkov <bp@xxxxxxx>
---
 arch/x86/kernel/cpu/intel_cacheinfo.c | 32 ++++++++++++++++++--------------
 1 file changed, 18 insertions(+), 14 deletions(-)

diff --git a/arch/x86/kernel/cpu/intel_cacheinfo.c b/arch/x86/kernel/cpu/intel_cacheinfo.c
index c55fb2cb2acc..24f749324c0f 100644
--- a/arch/x86/kernel/cpu/intel_cacheinfo.c
+++ b/arch/x86/kernel/cpu/intel_cacheinfo.c
@@ -811,7 +811,24 @@ static int __cache_amd_cpumap_setup(unsigned int cpu, int index,
 	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;
@@ -839,19 +856,6 @@ static int __cache_amd_cpumap_setup(unsigned int cpu, int index,
 						&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
 		return 0;
 
-- 
2.14.0.rc0