Commit-ID: 8d415ee225a3d15d3e3029524350e8237a4de7b8
Gitweb: http://git.kernel.org/tip/8d415ee225a3d15d3e3029524350e8237a4de7b8
Author: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
AuthorDate: Tue, 10 May 2016 09:20:33 +0200
Committer: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
CommitDate: Tue, 10 May 2016 09:28:31 +0200
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 <jbacik@xxxxxx>
Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: kernel-team <Kernel-team@xxxxxx>
Cc: Kan Liang <kan.liang@xxxxxxxxx>
Link: http://lkml.kernel.org/r/761b4a2a-0332-7954-f030-c6639f949612@xxxxxx
---
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 1f7fdb9..e4393bf 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. */
--
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