kernel.git/arch/x86/kernel/smpboot.c, branch linux-4.7.y

arch/x86: Handle non enumerated CPU after physical hotplug

2016-10-16T15:50:38Z

commit 2a51fe083eba7f99cbda72f5ef90cdf2f4df882c upstream. When a CPU is physically added to a system then the MADT table is not updated. If subsequently a kdump kernel is started on that physically added CPU then the ACPI enumeration fails to provide the information for this CPU which is now the boot CPU of the kdump kernel. As a consequence, generic_processor_info() is not invoked for that CPU so the number of enumerated processors is 0 and none of the initializations, including the logical package id management, are performed. We have code which relies on the correctness of the logical package map and other information which is initialized via generic_processor_info(). Executing such code will result in undefined behaviour or kernel crashes. This problem applies only to the kdump kernel because a normal kexec will switch to the original boot CPU, which is enumerated in MADT, before jumping into the kexec kernel. The boot code already has a check for num_processors equal 0 in prefill_possible_map(). We can use that check as an indicator that the enumeration of the boot CPU did not happen and invoke generic_processor_info() for it. That initializes the relevant data for the boot CPU and therefore prevents subsequent failure. [ tglx: Refined the code and rewrote the changelog ] Signed-off-by: Prarit Bhargava Fixes: 1f12e32f4cd5 ("x86/topology: Create logical package id") Cc: Peter Zijlstra Cc: Len Brown Cc: Borislav Petkov Cc: Andi Kleen Cc: Jiri Olsa Cc: Juergen Gross Cc: dyoung@redhat.com Cc: Eric Biederman Cc: kexec@lists.infradead.org Link: http://lkml.kernel.org/r/1475514432-27682-1-git-send-email-prarit@redhat.com Signed-off-by: Thomas Gleixner Signed-off-by: Greg Kroah-Hartman

x86/apic: Get rid of apic_version[] array

2016-10-16T15:50:38Z

commit cff9ab2b291e64259d97add48fe073c081afe4e2 upstream. The array has a size of MAX_LOCAL_APIC, which can be as large as 32k, so it can consume up to 128k. The array has been there forever and was never used for anything useful other than a version mismatch check which was introduced in 2009. There is no reason to store the version in an array. The kernel is not prepared to handle different APIC versions anyway, so the real important part is to detect a version mismatch and warn about it, which can be done with a single variable as well. [ tglx: Massaged changelog ] Signed-off-by: Denys Vlasenko CC: Andy Lutomirski CC: Borislav Petkov CC: Brian Gerst CC: Mike Travis Link: http://lkml.kernel.org/r/20160913181232.30815-1-dvlasenk@redhat.com Signed-off-by: Thomas Gleixner Signed-off-by: Greg Kroah-Hartman

Merge branch 'x86-asm-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

2016-05-16T22:15:17Z

Pull x86 asm updates from Ingo Molnar: "The main changes in this cycle were: - MSR access API fixes and enhancements (Andy Lutomirski) - early exception handling improvements (Andy Lutomirski) - user-space FS/GS prctl usage fixes and improvements (Andy Lutomirski) - Remove the cpu_has_*() APIs and replace them with equivalents (Borislav Petkov) - task switch micro-optimization (Brian Gerst) - 32-bit entry code simplification (Denys Vlasenko) - enhance PAT handling in enumated CPUs (Toshi Kani) ... and lots of other cleanups/fixlets" * 'x86-asm-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (70 commits) x86/arch_prctl/64: Restore accidentally removed put_cpu() in ARCH_SET_GS x86/entry/32: Remove asmlinkage_protect() x86/entry/32: Remove GET_THREAD_INFO() from entry code x86/entry, sched/x86: Don't save/restore EFLAGS on task switch x86/asm/entry/32: Simplify pushes of zeroed pt_regs->REGs selftests/x86/ldt_gdt: Test set_thread_area() deletion of an active segment x86/tls: Synchronize segment registers in set_thread_area() x86/asm/64: Rename thread_struct's fs and gs to fsbase and gsbase x86/arch_prctl/64: Remove FSBASE/GSBASE < 4G optimization x86/segments/64: When load_gs_index fails, clear the base x86/segments/64: When loadsegment(fs, ...) fails, clear the base x86/asm: Make asm/alternative.h safe from assembly x86/asm: Stop depending on ptrace.h in alternative.h x86/entry: Rename is_{ia32,x32}_task() to in_{ia32,x32}_syscall() x86/asm: Make sure verify_cpu() has a good stack x86/extable: Add a comment about early exception handlers x86/msr: Set the return value to zero when native_rdmsr_safe() fails x86/paravirt: Make "unsafe" MSR accesses unsafe even if PARAVIRT=y x86/paravirt: Add paravirt_{read,write}_msr() x86/msr: Carry on after a non-"safe" MSR access fails ...

x86/topology: Handle CPUID bogosity gracefully

2016-05-07T08:06:55Z

Joseph reported that a XEN guest dies with a division by 0 in the package topology setup code. This happens if cpu_info.x86_max_cores is zero. Handle that case and emit a warning. This does not fix the underlying XEN bug, but makes the code more robust. Reported-and-tested-by: Joseph Salisbury Cc: Peter Zijlstra Cc: Boris Ostrovsky Cc: David Vrabel Link: http://lkml.kernel.org/r/alpine.DEB.2.11.1605062046270.3540@nanos Signed-off-by: Thomas Gleixner

x86/cpufeature: Replace cpu_has_apic with boot_cpu_has() usage

2016-04-13T09:37:41Z

Signed-off-by: Borislav Petkov Cc: Andy Lutomirski Cc: Borislav Petkov Cc: Brian Gerst Cc: Denys Vlasenko Cc: H. Peter Anvin Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Thomas Gleixner Cc: iommu@lists.linux-foundation.org Cc: linux-pm@vger.kernel.org Cc: oprofile-list@lists.sf.net Link: http://lkml.kernel.org/r/1459801503-15600-8-git-send-email-bp@alien8.de Signed-off-by: Ingo Molnar

x86/cpu: Get rid of compute_unit_id

2016-03-29T08:45:04Z

It is cpu_core_id anyway. Signed-off-by: Borislav Petkov Link: http://lkml.kernel.org/r/1458917557-8757-3-git-send-email-bp@alien8.de Signed-off-by: Thomas Gleixner

x86/topology: Use total_cpus not nr_cpu_ids for logical packages

2016-03-19T09:26:40Z

nr_cpu_ids can be limited on the command line via nr_cpus=. That can break the logical package management because it results in a smaller number of packages, but the cpus to online are occupying the full package space as the hyper threads are enumerated after the physical cores typically. total_cpus is the real possible cpu space not limited by nr_cpus command line and gives us the proper number of packages. Reported-by: Mike Galbraith Fixes: 1f12e32f4cd5 ("x86/topology: Create logical package id") Signed-off-by: Thomas Gleixner Cc: Xiong Zhou Cc: Ingo Molnar Cc: Borislav Petkov Cc: Andreas Herrmann Link: http://lkml.kernel.org/r/alpine.DEB.2.11.1603181254330.3978@nanos

x86/topology: Fix Intel HT disable

2016-03-19T09:26:40Z

As per the comment in the code; due to BIOS it is sometimes impossible to know if there actually are smp siblings until the machine is fully enumerated. So we rather overestimate the number of possible packages. Fixes: 1f12e32f4cd5 ("x86/topology: Create logical package id") Signed-off-by: Peter Zijlstra (Intel) Cc: aherrmann@suse.com Cc: jencce.kernel@gmail.com Cc: bp@alien8.de Cc: Mike Galbraith Link: http://lkml.kernel.org/r/20160318150538.611014173@infradead.org Signed-off-by: Thomas Gleixner

x86/topology: Fix logical package mapping

2016-03-19T09:26:40Z

That first branch testing pkg against __max_logical_packages is wrong, because if the first pkg id is larger, then the find_first_zero will find us logical package id 0. However, if the second pkg id is indeed 0, we'll again claim it without testing if it was already taken. Also, it fails to print the mapping. Fixes: 1f12e32f4cd5 ("x86/topology: Create logical package id") Reported-by: Xiong Zhou Signed-off-by: Peter Zijlstra (Intel) Cc: aherrmann@suse.com Cc: bp@alien8.de Cc: Mike Galbraith Link: http://lkml.kernel.org/r/20160317095220.GO6344@twins.programming.kicks-ass.net Link: http://lkml.kernel.org/r/20160318150538.482393396@infradead.org Signed-off-by: Thomas Gleixner

Merge branch 'smp-hotplug-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

2016-03-15T20:50:29Z

Pull cpu hotplug updates from Thomas Gleixner: "This is the first part of the ongoing cpu hotplug rework: - Initial implementation of the state machine - Runs all online and prepare down callbacks on the plugged cpu and not on some random processor - Replaces busy loop waiting with completions - Adds tracepoints so the states can be followed" More detailed commentary on this work from an earlier email: "What's wrong with the current cpu hotplug infrastructure? - Asymmetry The hotplug notifier mechanism is asymmetric versus the bringup and teardown. This is mostly caused by the notifier mechanism. - Largely undocumented dependencies While some notifiers use explicitely defined notifier priorities, we have quite some notifiers which use numerical priorities to express dependencies without any documentation why. - Control processor driven Most of the bringup/teardown of a cpu is driven by a control processor. While it is understandable, that preperatory steps, like idle thread creation, memory allocation for and initialization of essential facilities needs to be done before a cpu can boot, there is no reason why everything else must run on a control processor. Before this patch series, bringup looks like this: Control CPU Booting CPU do preparatory steps kick cpu into life do low level init sync with booting cpu sync with control cpu bring the rest up - All or nothing approach There is no way to do partial bringups. That's something which is really desired because we waste e.g. at boot substantial amount of time just busy waiting that the cpu comes to life. That's stupid as we could very well do preparatory steps and the initial IPI for other cpus and then go back and do the necessary low level synchronization with the freshly booted cpu. - Minimal debuggability Due to the notifier based design, it's impossible to switch between two stages of the bringup/teardown back and forth in order to test the correctness. So in many hotplug notifiers the cancel mechanisms are either not existant or completely untested. - Notifier [un]registering is tedious To [un]register notifiers we need to protect against hotplug at every callsite. There is no mechanism that bringup/teardown callbacks are issued on the online cpus, so every caller needs to do it itself. That also includes error rollback. What's the new design? The base of the new design is a symmetric state machine, where both the control processor and the booting/dying cpu execute a well defined set of states. Each state is symmetric in the end, except for some well defined exceptions, and the bringup/teardown can be stopped and reversed at almost all states. So the bringup of a cpu will look like this in the future: Control CPU Booting CPU do preparatory steps kick cpu into life do low level init sync with booting cpu sync with control cpu bring itself up The synchronization step does not require the control cpu to wait. That mechanism can be done asynchronously via a worker or some other mechanism. The teardown can be made very similar, so that the dying cpu cleans up and brings itself down. Cleanups which need to be done after the cpu is gone, can be scheduled asynchronously as well. There is a long way to this, as we need to refactor the notion when a cpu is available. Today we set the cpu online right after it comes out of the low level bringup, which is not really correct. The proper mechanism is to set it to available, i.e. cpu local threads, like softirqd, hotplug thread etc. can be scheduled on that cpu, and once it finished all booting steps, it's set to online, so general workloads can be scheduled on it. The reverse happens on teardown. First thing to do is to forbid scheduling of general workloads, then teardown all the per cpu resources and finally shut it off completely. This patch series implements the basic infrastructure for this at the core level. This includes the following: - Basic state machine implementation with well defined states, so ordering and prioritization can be expressed. - Interfaces to [un]register state callbacks This invokes the bringup/teardown callback on all online cpus with the proper protection in place and [un]installs the callbacks in the state machine array. For callbacks which have no particular ordering requirement we have a dynamic state space, so that drivers don't have to register an explicit hotplug state. If a callback fails, the code automatically does a rollback to the previous state. - Sysfs interface to drive the state machine to a particular step. This is only partially functional today. Full functionality and therefor testability will be achieved once we converted all existing hotplug notifiers over to the new scheme. - Run all CPU_ONLINE/DOWN_PREPARE notifiers on the booting/dying processor: Control CPU Booting CPU do preparatory steps kick cpu into life do low level init sync with booting cpu sync with control cpu wait for boot bring itself up Signal completion to control cpu In a previous step of this work we've done a full tree mechanical conversion of all hotplug notifiers to the new scheme. The balance is a net removal of about 4000 lines of code. This is not included in this series, as we decided to take a different approach. Instead of mechanically converting everything over, we will do a proper overhaul of the usage sites one by one so they nicely fit into the symmetric callback scheme. I decided to do that after I looked at the ugliness of some of the converted sites and figured out that their hotplug mechanism is completely buggered anyway. So there is no point to do a mechanical conversion first as we need to go through the usage sites one by one again in order to achieve a full symmetric and testable behaviour" * 'smp-hotplug-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (23 commits) cpu/hotplug: Document states better cpu/hotplug: Fix smpboot thread ordering cpu/hotplug: Remove redundant state check cpu/hotplug: Plug death reporting race rcu: Make CPU_DYING_IDLE an explicit call cpu/hotplug: Make wait for dead cpu completion based cpu/hotplug: Let upcoming cpu bring itself fully up arch/hotplug: Call into idle with a proper state cpu/hotplug: Move online calls to hotplugged cpu cpu/hotplug: Create hotplug threads cpu/hotplug: Split out the state walk into functions cpu/hotplug: Unpark smpboot threads from the state machine cpu/hotplug: Move scheduler cpu_online notifier to hotplug core cpu/hotplug: Implement setup/removal interface cpu/hotplug: Make target state writeable cpu/hotplug: Add sysfs state interface cpu/hotplug: Hand in target state to _cpu_up/down cpu/hotplug: Convert the hotplugged cpu work to a state machine cpu/hotplug: Convert to a state machine for the control processor cpu/hotplug: Add tracepoints ...