[GIT PULL] x86 generic hotplug changes for v3.8
Linus, Please pull the latest x86-bsp-hotplug-for-linus git tree from: git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git x86-bsp-hotplug-for-linus HEAD: a71c8bc5dfefbbf80ef90739791554ef7ea4401b x86, topology: Debug CPU0 hotplug This tree enables CPU#0 (the boot processor) to be onlined/offlined on x86, just like any other CPU. Enabled on Intel CPUs for now. Allowing this required the identification and fixing of latent CPU#0 assumptions (such as CPU#0 initializations, etc.) in the x86 architecture code, plus the identification of barriers to BSP-offlining, such as active PIC interrupts which can only be serviced on the BSP. It's behind a default-off option, and there's a debug option that allows the automatic testing of this feature. The motivation of this feature is to allow and prepare for true CPU-hotplug hardware support: recent changes to MCE support enable us to detect a deteriorating but not yet hard-failing L1/L2 cache on a CPU that could be soft-unplugged - or a failing L3 cache on a multi-socket system. Note that true hardware hot-plug is not yet fully enabled by this, because that requires a special platform wakeup sequence to be sent to the freshly powered up CPU#0. Future patches for this are planned, once such a platform exists. Chicken and egg ... out-of-topic modifications in x86-bsp-hotplug-for-linus: kernel/cpu.c # 6e32d47: kernel/cpu.c: Add comment for pri Thanks, Ingo --> Fenghua Yu (14): doc: Add x86 CPU0 online/offline feature x86, Kconfig: Add config switch for CPU0 hotplug x86, topology: Don't offline CPU0 if any PIC irq can not be migrated out of it x86, hotplug: Support functions for CPU0 online/offline x86, hotplug, suspend: Online CPU0 for suspend or hibernate kernel/cpu.c: Add comment for priority in cpu_hotplug_pm_callback x86-64, hotplug: Add start_cpu0() entry point to head_64.S x86-32, hotplug: Add start_cpu0() entry point to head_32.S x86, hotplug: Wake up CPU0 via NMI instead of INIT, SIPI, SIPI x86, hotplug: During CPU0 online, enable x2apic, set_numa_node. x86, hotplug: The first online processor saves the MTRR state x86, hotplug: Handle retrigger irq by the first available CPU x86/i387.c: Initialize thread xstate only on CPU0 only once x86, topology: Debug CPU0 hotplug Documentation/cpu-hotplug.txt | 24 ++ Documentation/kernel-parameters.txt | 14 arch/x86/Kconfig| 44 +++ arch/x86/include/asm/cpu.h | 4 + arch/x86/include/asm/smp.h | 1 + arch/x86/kernel/apic/io_apic.c | 4 +- arch/x86/kernel/cpu/common.c| 5 +- arch/x86/kernel/cpu/mtrr/main.c | 9 ++- arch/x86/kernel/head_32.S | 13 arch/x86/kernel/head_64.S | 16 arch/x86/kernel/i387.c | 6 +- arch/x86/kernel/smpboot.c | 149 +--- arch/x86/kernel/topology.c | 101 ++-- arch/x86/power/cpu.c| 82 kernel/cpu.c| 5 ++ 15 files changed, 436 insertions(+), 41 deletions(-) diff --git a/Documentation/cpu-hotplug.txt b/Documentation/cpu-hotplug.txt index 66ef8f3..9f40135 100644 --- a/Documentation/cpu-hotplug.txt +++ b/Documentation/cpu-hotplug.txt @@ -207,6 +207,30 @@ by making it not-removable. In such cases you will also notice that the online file is missing under cpu0. +Q: Is CPU0 removable on X86? +A: Yes. If kernel is compiled with CONFIG_BOOTPARAM_HOTPLUG_CPU0=y, CPU0 is +removable by default. Otherwise, CPU0 is also removable by kernel option +cpu0_hotplug. + +But some features depend on CPU0. Two known dependencies are: + +1. Resume from hibernate/suspend depends on CPU0. Hibernate/suspend will fail if +CPU0 is offline and you need to online CPU0 before hibernate/suspend can +continue. +2. PIC interrupts also depend on CPU0. CPU0 can't be removed if a PIC interrupt +is detected. + +It's said poweroff/reboot may depend on CPU0 on some machines although I haven't +seen any poweroff/reboot failure so far after CPU0 is offline on a few tested +machines. + +Please let me know if you know or see any other dependencies of CPU0. + +If the dependencies are under your control, you can turn on CPU0 hotplug feature +either by CONFIG_BOOTPARAM_HOTPLUG_CPU0 or by kernel parameter cpu0_hotplug. + +--Fenghua Yu + Q: How do i find out if a particular CPU is not removable? A: Depending on the implementation, some architectures may show this by the absence of the "online" file. This is done if it can be determined ahead of diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt index 9776f06..f7cbe1d 100644 --- a/Documentation/kernel-parameters.txt +++ b/Documentation/kernel-parameters.txt
[GIT PULL] x86 generic hotplug changes for v3.8
Linus, Please pull the latest x86-bsp-hotplug-for-linus git tree from: git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git x86-bsp-hotplug-for-linus HEAD: a71c8bc5dfefbbf80ef90739791554ef7ea4401b x86, topology: Debug CPU0 hotplug This tree enables CPU#0 (the boot processor) to be onlined/offlined on x86, just like any other CPU. Enabled on Intel CPUs for now. Allowing this required the identification and fixing of latent CPU#0 assumptions (such as CPU#0 initializations, etc.) in the x86 architecture code, plus the identification of barriers to BSP-offlining, such as active PIC interrupts which can only be serviced on the BSP. It's behind a default-off option, and there's a debug option that allows the automatic testing of this feature. The motivation of this feature is to allow and prepare for true CPU-hotplug hardware support: recent changes to MCE support enable us to detect a deteriorating but not yet hard-failing L1/L2 cache on a CPU that could be soft-unplugged - or a failing L3 cache on a multi-socket system. Note that true hardware hot-plug is not yet fully enabled by this, because that requires a special platform wakeup sequence to be sent to the freshly powered up CPU#0. Future patches for this are planned, once such a platform exists. Chicken and egg ... out-of-topic modifications in x86-bsp-hotplug-for-linus: kernel/cpu.c # 6e32d47: kernel/cpu.c: Add comment for pri Thanks, Ingo -- Fenghua Yu (14): doc: Add x86 CPU0 online/offline feature x86, Kconfig: Add config switch for CPU0 hotplug x86, topology: Don't offline CPU0 if any PIC irq can not be migrated out of it x86, hotplug: Support functions for CPU0 online/offline x86, hotplug, suspend: Online CPU0 for suspend or hibernate kernel/cpu.c: Add comment for priority in cpu_hotplug_pm_callback x86-64, hotplug: Add start_cpu0() entry point to head_64.S x86-32, hotplug: Add start_cpu0() entry point to head_32.S x86, hotplug: Wake up CPU0 via NMI instead of INIT, SIPI, SIPI x86, hotplug: During CPU0 online, enable x2apic, set_numa_node. x86, hotplug: The first online processor saves the MTRR state x86, hotplug: Handle retrigger irq by the first available CPU x86/i387.c: Initialize thread xstate only on CPU0 only once x86, topology: Debug CPU0 hotplug Documentation/cpu-hotplug.txt | 24 ++ Documentation/kernel-parameters.txt | 14 arch/x86/Kconfig| 44 +++ arch/x86/include/asm/cpu.h | 4 + arch/x86/include/asm/smp.h | 1 + arch/x86/kernel/apic/io_apic.c | 4 +- arch/x86/kernel/cpu/common.c| 5 +- arch/x86/kernel/cpu/mtrr/main.c | 9 ++- arch/x86/kernel/head_32.S | 13 arch/x86/kernel/head_64.S | 16 arch/x86/kernel/i387.c | 6 +- arch/x86/kernel/smpboot.c | 149 +--- arch/x86/kernel/topology.c | 101 ++-- arch/x86/power/cpu.c| 82 kernel/cpu.c| 5 ++ 15 files changed, 436 insertions(+), 41 deletions(-) diff --git a/Documentation/cpu-hotplug.txt b/Documentation/cpu-hotplug.txt index 66ef8f3..9f40135 100644 --- a/Documentation/cpu-hotplug.txt +++ b/Documentation/cpu-hotplug.txt @@ -207,6 +207,30 @@ by making it not-removable. In such cases you will also notice that the online file is missing under cpu0. +Q: Is CPU0 removable on X86? +A: Yes. If kernel is compiled with CONFIG_BOOTPARAM_HOTPLUG_CPU0=y, CPU0 is +removable by default. Otherwise, CPU0 is also removable by kernel option +cpu0_hotplug. + +But some features depend on CPU0. Two known dependencies are: + +1. Resume from hibernate/suspend depends on CPU0. Hibernate/suspend will fail if +CPU0 is offline and you need to online CPU0 before hibernate/suspend can +continue. +2. PIC interrupts also depend on CPU0. CPU0 can't be removed if a PIC interrupt +is detected. + +It's said poweroff/reboot may depend on CPU0 on some machines although I haven't +seen any poweroff/reboot failure so far after CPU0 is offline on a few tested +machines. + +Please let me know if you know or see any other dependencies of CPU0. + +If the dependencies are under your control, you can turn on CPU0 hotplug feature +either by CONFIG_BOOTPARAM_HOTPLUG_CPU0 or by kernel parameter cpu0_hotplug. + +--Fenghua Yu fenghua...@intel.com + Q: How do i find out if a particular CPU is not removable? A: Depending on the implementation, some architectures may show this by the absence of the online file. This is done if it can be determined ahead of diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt index 9776f06..f7cbe1d 100644 --- a/Documentation/kernel-parameters.txt +++
