diff options
author | Fenghua Yu <fenghua.yu@intel.com> | 2012-11-13 19:32:40 (GMT) |
---|---|---|
committer | H. Peter Anvin <hpa@linux.intel.com> | 2012-11-14 17:39:47 (GMT) |
commit | 4d25031a81d3cd32edc00de6596db76cc4010685 (patch) | |
tree | f0786770dd05073e31781099b6645a5302a95e35 /arch | |
parent | 80aa1dff65717e7518647d4e27d1d3dcea5818e6 (diff) | |
download | linux-fsl-qoriq-4d25031a81d3cd32edc00de6596db76cc4010685.tar.xz |
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')
-rw-r--r-- | arch/x86/kernel/topology.c | 50 |
1 files changed, 43 insertions, 7 deletions
diff --git a/arch/x86/kernel/topology.c b/arch/x86/kernel/topology.c index 76ee977..0e7b4a7 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); |