1 files changed, 18 insertions, 0 deletions

diff --git a/arch/x86/kernel/cpu/amd.c b/arch/x86/kernel/cpu/amd.c
index 1c67ca100e4c..146bb6218eec 100644
--- a/arch/x86/kernel/cpu/amd.c
+++ b/arch/x86/kernel/cpu/amd.c
@@ -580,6 +580,24 @@ static void __cpuinit init_amd(struct cpuinfo_x86 *c)
                 }
         }
 
+        /* re-enable TopologyExtensions if switched off by BIOS */
+        if ((c->x86 == 0x15) &&
+            (c->x86_model >= 0x10) && (c->x86_model <= 0x1f) &&
+            !cpu_has(c, X86_FEATURE_TOPOEXT)) {
+                u64 val;
+
+                if (!rdmsrl_amd_safe(0xc0011005, &val)) {
+                        val |= 1ULL << 54;
+                        wrmsrl_amd_safe(0xc0011005, val);
+                        rdmsrl(0xc0011005, val);
+                        if (val & (1ULL << 54)) {
+                                set_cpu_cap(c, X86_FEATURE_TOPOEXT);
+                                printk(KERN_INFO FW_INFO "CPU: Re-enabling "
+                                  "disabled Topology Extensions Support\n");
+                        }
+                }
+        }
+
         cpu_detect_cache_sizes(c);
 
         /* Multi core CPU? */