linux-kernel - [PATCH] x86/amd: Derive L3 shared_cpu_map from cpu_llc_shared

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Date:   Thu, 20 Jul 2017 04:52:08 -0500
From:   Suravee Suthikulpanit <suravee.suthikulpanit@....com>
To:     linux-kernel@...r.kernel.org, x86@...nel.org
Cc:     tglx@...utronix.de, mingo@...hat.com, hpa@...or.com, bp@...e.de,
        Suravee Suthikulpanit <suravee.suthikulpanit@....com>
Subject: [PATCH] x86/amd: Derive L3 shared_cpu_map from cpu_llc_shared_mask

With X86_FEATURE_TOPOEXT, current logic default to using APIC ID
to calculate cpumask for shared_cpu_map. However, since APIC IDs
are not guarantee to be contiguous for cores across different L3,
such as in family17h system w/ downcore configuration.
This results in incorrect L3 shared_cpu_map.

Instead, it should be safe to always use the pre-calculated
cpu_llc_shared_mask to derive L3 shared_cpu_map.

Signed-off-by: Suravee Suthikulpanit <suravee.suthikulpanit@....com>
---
 arch/x86/kernel/cpu/intel_cacheinfo.c | 28 ++++++++++++++--------------
 1 file changed, 14 insertions(+), 14 deletions(-)

diff --git a/arch/x86/kernel/cpu/intel_cacheinfo.c b/arch/x86/kernel/cpu/intel_cacheinfo.c
index c55fb2c..10427bb 100644
--- a/arch/x86/kernel/cpu/intel_cacheinfo.c
+++ b/arch/x86/kernel/cpu/intel_cacheinfo.c
@@ -811,7 +811,20 @@ 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)) {
+	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 +852,6 @@ 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;
 
-- 
2.7.4