[patch V2 11/12] x86/cpu/AMD: Evaluate smp_num_siblings early

From: Thomas Gleixner <tglx@linutronix.de>
To: speck@linutronix.de
Subject: [patch V2 11/12] x86/cpu/AMD: Evaluate smp_num_siblings early
Date: Wed, 06 Jun 2018 21:27:25 +0200	[thread overview]
Message-ID: <20180606192807.847202262@linutronix.de> (raw)
In-Reply-To: 20180606192714.754943543@linutronix.de

Subject: [patch V2 11/12] x86/cpu/AMD: Evaluate smp_num_siblings early
From: Thomas Gleixner <tglx@linutronix.de>

To support force disabling of SMT it's required to know the number of
thread siblings early. amd_get_topology() cannot be called before the APIC
driver is selected, so split out the part which initializes
smp_num_siblings and invoke it from amd_early_init().

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
---
 arch/x86/kernel/cpu/amd.c |   14 ++++++++++++++
 1 file changed, 14 insertions(+)

--- a/arch/x86/kernel/cpu/amd.c
+++ b/arch/x86/kernel/cpu/amd.c
@@ -315,6 +315,18 @@ static void legacy_fixup_core_id(struct
 	c->cpu_core_id %= cus_per_node;
 }
 
+
+static void amd_get_topology_early(struct cpuinfo_x86 *c)
+{
+	if (boot_cpu_has(X86_FEATURE_TOPOEXT) &&
+	    c->extended_cpuid_level >= 0x80000008) {
+		u32 eax, ebx, ecx, edx;
+
+		cpuid(0x8000001e, &eax, &ebx, &ecx, &edx);
+		smp_num_siblings = ((ebx >> 8) & 0xff) + 1;
+	}
+}
+
 /*
  * Fixup core topology information for
  * (1) AMD multi-node processors
@@ -681,6 +693,8 @@ static void early_init_amd(struct cpuinf
 		set_cpu_bug(c, X86_BUG_AMD_E400);
 
 	early_detect_mem_encrypt(c);
+
+	amd_get_topology_early(c);
 }
 
 static void init_amd_k8(struct cpuinfo_x86 *c)
