From 8d415ee225a3d15d3e3029524350e8237a4de7b8 Mon Sep 17 00:00:00 2001 From: Thomas Gleixner Date: Tue, 10 May 2016 09:20:33 +0200 Subject: [PATCH] x86/topology: Set x86_max_cores to 1 for CONFIG_SMP=n Josef reported that the uncore driver trips over with CONFIG_SMP=n because x86_max_cores is 16 instead of 12. The reason is, that for SMP=n the extended topology detection is a NOOP and the cache leaf is used to determine the number of cores. That's wrong in two aspects: 1) The cache leaf enumerates the maximum addressable number of cores in the package, which is obviously not correct 2) UP has no business with topology bits at all. Make intel_num_cpu_cores() return 1 for CONFIG_SMP=n Reported-by: Josef Bacik Signed-off-by: Thomas Gleixner Cc: Peter Zijlstra Cc: kernel-team Cc: Kan Liang Link: http://lkml.kernel.org/r/761b4a2a-0332-7954-f030-c6639f949612@fb.com --- arch/x86/kernel/cpu/intel.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/arch/x86/kernel/cpu/intel.c b/arch/x86/kernel/cpu/intel.c index 1f7fdb91a818..e4393bfc7f0d 100644 --- a/arch/x86/kernel/cpu/intel.c +++ b/arch/x86/kernel/cpu/intel.c @@ -336,7 +336,7 @@ static int intel_num_cpu_cores(struct cpuinfo_x86 *c) { unsigned int eax, ebx, ecx, edx; - if (c->cpuid_level < 4) + if (!IS_ENABLED(CONFIG_SMP) || c->cpuid_level < 4) return 1; /* Intel has a non-standard dependency on %ecx for this CPUID level. */