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x86, topology: Don't offline CPU0 if any PIC irq can not be migrated out of it

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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>
This commit is contained in:
Fenghua Yu 2012-11-13 11:32:40 -08:00 committed by H. Peter Anvin
parent 80aa1dff65
commit 4d25031a81
1 changed files with 44 additions and 8 deletions
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52
arch/x86/kernel/topology.c
View File

@ -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);
/*
* 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.
*
* Also certain PCI quirks require not to enable hotplug control
* for all CPU's.
* Currently CPU0 is only hotpluggable on Intel platforms. Other
* vendors can add hotplug support later.
*/
if (num)
if (c->x86_vendor != X86_VENDOR_INTEL)
cpu0_hotpluggable = 0;
/*
* Two known BSP/CPU0 dependencies: Resume from suspend/hibernate
* depends on BSP. PIC interrupts depend on BSP.
*
* 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 == 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);