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authorFenghua Yu <fenghua.yu@intel.com>2012-11-13 11:32:40 -0800
committerH. Peter Anvin <hpa@linux.intel.com>2012-11-14 09:39:47 -0800
commit4d25031a81d3cd32edc00de6596db76cc4010685 (patch)
treef0786770dd05073e31781099b6645a5302a95e35 /arch/x86/kernel/topology.c
parent80aa1dff65717e7518647d4e27d1d3dcea5818e6 (diff)
downloadblackbird-op-linux-4d25031a81d3cd32edc00de6596db76cc4010685.tar.gz
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x86, topology: Don't offline CPU0 if any PIC irq can not be migrated out of it
If CONFIG_BOOTPARAM_HOTPLUG_CPU is turned on, CPU0 hotplug feature is enabled by default. If CONFIG_BOOTPARAM_HOTPLUG_CPU is not turned on, CPU0 hotplug feature is not enabled by default. The kernel parameter cpu0_hotplug can enable CPU0 hotplug feature at boot. Currently the feature is supported on Intel platforms only. Signed-off-by: Fenghua Yu <fenghua.yu@intel.com> Link: http://lkml.kernel.org/r/1352835171-3958-4-git-send-email-fenghua.yu@intel.com Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
Diffstat (limited to 'arch/x86/kernel/topology.c')
-rw-r--r--arch/x86/kernel/topology.c50
1 files changed, 43 insertions, 7 deletions
diff --git a/arch/x86/kernel/topology.c b/arch/x86/kernel/topology.c
index 76ee97709a00..0e7b4a7a7fb8 100644
--- a/arch/x86/kernel/topology.c
+++ b/arch/x86/kernel/topology.c
@@ -30,23 +30,59 @@
#include <linux/mmzone.h>
#include <linux/init.h>
#include <linux/smp.h>
+#include <linux/irq.h>
#include <asm/cpu.h>
static DEFINE_PER_CPU(struct x86_cpu, cpu_devices);
#ifdef CONFIG_HOTPLUG_CPU
+
+#ifdef CONFIG_BOOTPARAM_HOTPLUG_CPU0
+static int cpu0_hotpluggable = 1;
+#else
+static int cpu0_hotpluggable;
+static int __init enable_cpu0_hotplug(char *str)
+{
+ cpu0_hotpluggable = 1;
+ return 1;
+}
+
+__setup("cpu0_hotplug", enable_cpu0_hotplug);
+#endif
+
int __ref arch_register_cpu(int num)
{
+ struct cpuinfo_x86 *c = &cpu_data(num);
+
+ /*
+ * Currently CPU0 is only hotpluggable on Intel platforms. Other
+ * vendors can add hotplug support later.
+ */
+ if (c->x86_vendor != X86_VENDOR_INTEL)
+ cpu0_hotpluggable = 0;
+
/*
- * CPU0 cannot be offlined due to several
- * restrictions and assumptions in kernel. This basically
- * doesn't add a control file, one cannot attempt to offline
- * BSP.
+ * Two known BSP/CPU0 dependencies: Resume from suspend/hibernate
+ * depends on BSP. PIC interrupts depend on BSP.
*
- * Also certain PCI quirks require not to enable hotplug control
- * for all CPU's.
+ * If the BSP depencies are under control, one can tell kernel to
+ * enable BSP hotplug. This basically adds a control file and
+ * one can attempt to offline BSP.
*/
- if (num)
+ if (num == 0 && cpu0_hotpluggable) {
+ unsigned int irq;
+ /*
+ * We won't take down the boot processor on i386 if some
+ * interrupts only are able to be serviced by the BSP in PIC.
+ */
+ for_each_active_irq(irq) {
+ if (!IO_APIC_IRQ(irq) && irq_has_action(irq)) {
+ cpu0_hotpluggable = 0;
+ break;
+ }
+ }
+ }
+ if (num || cpu0_hotpluggable)
per_cpu(cpu_devices, num).cpu.hotpluggable = 1;
return register_cpu(&per_cpu(cpu_devices, num).cpu, num);
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