x86/CPU/AMD: Move TOPOEXT reenablement before reading smp_num_siblings

The TOPOEXT reenablement is a workaround for broken BIOSen which didn't
enable the CPUID bit. amd_get_topology_early(), however, relies on
that bit being set so that it can read out the CPUID leaf and set
smp_num_siblings properly.

Move the reenablement up to early_init_amd(). While at it, simplify
amd_get_topology_early().
Signed-off-by: Borislav Petkov <bp@suse.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

CVE-2018-3620
CVE-2018-3646
Signed-off-by: Stefan Bader <stefan.bader@canonical.com>

arch/x86/kernel/cpu/amd.c

@@ -294,12 +294,8 @@ static int nearby_node(int apicid)
 static void amd_get_topology_early(struct cpuinfo_x86 *c)
 {
 #ifdef CONFIG_SMP
-	if (boot_cpu_has(X86_FEATURE_TOPOEXT)) {
-		u32 eax, ebx, ecx, edx;
-
-		cpuid(0x8000001e, &eax, &ebx, &ecx, &edx);
-		smp_num_siblings = ((ebx >> 8) & 0xff) + 1;
-	}
+	if (boot_cpu_has(X86_FEATURE_TOPOEXT))
+		smp_num_siblings = ((cpuid_ebx(0x8000001e) >> 8) & 0x3) + 1;
 #endif
 }
 
@@ -325,7 +321,7 @@ static void amd_get_topology(struct cpuinfo_x86 *c)
 		node_id = ecx & 7;
 
 		/* get compute unit information */
-		cores_per_cu = smp_num_siblings = ((ebx >> 8) & 3) + 1;
+		cores_per_cu = smp_num_siblings;
 		c->x86_max_cores /= smp_num_siblings;
 		c->compute_unit_id = ebx & 0xff;
 	} else if (cpu_has(c, X86_FEATURE_NODEID_MSR)) {
@@ -556,6 +552,8 @@ static void bsp_init_amd(struct cpuinfo_x86 *c)
 
 static void early_init_amd(struct cpuinfo_x86 *c)
 {
+	u64 value;
+
 	early_init_amd_mc(c);
 
 	/*
@@ -607,6 +605,20 @@ static void early_init_amd(struct cpuinfo_x86 *c)
 	if (c->x86 == 0x16 && c->x86_model <= 0xf)
 		msr_set_bit(MSR_AMD64_LS_CFG, 15);
 
+	/* Re-enable TopologyExtensions if switched off by BIOS */
+	if (c->x86 == 0x15 &&
+	    (c->x86_model >= 0x10 && c->x86_model <= 0x6f) &&
+	    !cpu_has(c, X86_FEATURE_TOPOEXT)) {
+
+		if (msr_set_bit(0xc0011005, 54) > 0) {
+			rdmsrl(0xc0011005, value);
+			if (value & BIT_64(54)) {
+				set_cpu_cap(c, X86_FEATURE_TOPOEXT);
+				pr_info_once(FW_INFO "CPU: Re-enabling disabled Topology Extensions Support.\n");
+			}
+		}
+	}
+
 	amd_get_topology_early(c);
 }
 
@@ -702,19 +714,6 @@ static void init_amd_bd(struct cpuinfo_x86 *c)
 {
 	u64 value;
 
-	/* re-enable TopologyExtensions if switched off by BIOS */
-	if ((c->x86_model >= 0x10) && (c->x86_model <= 0x1f) &&
-	    !cpu_has(c, X86_FEATURE_TOPOEXT)) {
-
-		if (msr_set_bit(0xc0011005, 54) > 0) {
-			rdmsrl(0xc0011005, value);
-			if (value & BIT_64(54)) {
-				set_cpu_cap(c, X86_FEATURE_TOPOEXT);
-				pr_info(FW_INFO "CPU: Re-enabling disabled Topology Extensions Support.\n");
-			}
-		}
-	}
-
 	/*
 	 * The way access filter has a performance penalty on some workloads.
 	 * Disable it on the affected CPUs.