From: tip-bot for Thomas Gleixner <tipbot@zytor.com>
To: linux-tip-commits@vger.kernel.org
Cc: Kernel-team@fb.com, tglx@linutronix.de, mingo@kernel.org,
linux-kernel@vger.kernel.org, hpa@zytor.com,
peterz@infradead.org, kan.liang@intel.com, jbacik@fb.com
Subject: [tip:x86/urgent] x86/topology: Set x86_max_cores to 1 for CONFIG_SMP=n
Date: Tue, 10 May 2016 00:33:44 -0700 [thread overview]
Message-ID: <tip-8d415ee225a3d15d3e3029524350e8237a4de7b8@git.kernel.org> (raw)
In-Reply-To: <761b4a2a-0332-7954-f030-c6639f949612@fb.com>
Commit-ID: 8d415ee225a3d15d3e3029524350e8237a4de7b8
Gitweb: http://git.kernel.org/tip/8d415ee225a3d15d3e3029524350e8237a4de7b8
Author: Thomas Gleixner <tglx@linutronix.de>
AuthorDate: Tue, 10 May 2016 09:20:33 +0200
Committer: Thomas Gleixner <tglx@linutronix.de>
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@fb.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: kernel-team <Kernel-team@fb.com>
Cc: Kan Liang <kan.liang@intel.com>
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 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. */
prev parent reply other threads:[~2016-05-10 7:35 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-05-09 18:39 Regression introduced by cf6d445f68974d0b15a14cf6021be38a91f2b5d8 Josef Bacik
2016-05-09 19:48 ` Thomas Gleixner
2016-05-09 20:55 ` Liang, Kan
2016-05-10 6:51 ` Peter Zijlstra
2016-05-10 7:33 ` tip-bot for Thomas Gleixner [this message]
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