linux-kernel - [PATCH 4.9 048/107] x86/cpu/AMD: Evaluate smp_num

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Message-Id: <20180814171524.179842469@linuxfoundation.org>
Date:   Tue, 14 Aug 2018 19:17:11 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...nel.org>,
        David Woodhouse <dwmw@...zon.co.uk>
Subject: [PATCH 4.9 048/107] x86/cpu/AMD: Evaluate smp_num_siblings early

4.9-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Thomas Gleixner <tglx@...utronix.de>

commit 1e1d7e25fd759eddf96d8ab39d0a90a1979b2d8c upstream

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().

[dwmw2: Backport to 4.9]

Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
Acked-by: Ingo Molnar <mingo@...nel.org>
Signed-off-by: David Woodhouse <dwmw@...zon.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 arch/x86/kernel/cpu/amd.c |   15 ++++++++++++++-
 1 file changed, 14 insertions(+), 1 deletion(-)

--- a/arch/x86/kernel/cpu/amd.c
+++ b/arch/x86/kernel/cpu/amd.c
@@ -296,13 +296,24 @@ static int nearby_node(int apicid)
 }
 #endif
 
+#ifdef CONFIG_SMP
+
+static void amd_get_topology_early(struct cpuinfo_x86 *c)
+{
+	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;
+	}
+}
+
 /*
  * Fixup core topology information for
  * (1) AMD multi-node processors
  *     Assumption: Number of cores in each internal node is the same.
  * (2) AMD processors supporting compute units
  */
-#ifdef CONFIG_SMP
 static void amd_get_topology(struct cpuinfo_x86 *c)
 {
 	u8 node_id;
@@ -633,6 +644,8 @@ static void early_init_amd(struct cpuinf
 	 */
 	if (cpu_has_amd_erratum(c, amd_erratum_400))
 		set_cpu_bug(c, X86_BUG_AMD_E400);
+
+	amd_get_topology_early(c);
 }
 
 static void init_amd_k8(struct cpuinfo_x86 *c)