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* x86/speculation: Remove redundant arch_smt_update() invocationZhenzhong Duan2020-04-241-4/+1
| | | | | | | | | | | | | | | | | | | | | | | | commit 34d66caf251df91ff27b24a3a786810d29989eca upstream. With commit a74cfffb03b7 ("x86/speculation: Rework SMT state change"), arch_smt_update() is invoked from each individual CPU hotplug function. Therefore the extra arch_smt_update() call in the sysfs SMT control is redundant. Fixes: a74cfffb03b7 ("x86/speculation: Rework SMT state change") Signed-off-by: Zhenzhong Duan <zhenzhong.duan@oracle.com> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Cc: <konrad.wilk@oracle.com> Cc: <dwmw@amazon.co.uk> Cc: <bp@suse.de> Cc: <srinivas.eeda@oracle.com> Cc: <peterz@infradead.org> Cc: <hpa@zytor.com> Link: https://lkml.kernel.org/r/e2e064f2-e8ef-42ca-bf4f-76b612964752@default Cc: Guenter Roeck <linux@roeck-us.net> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
* cpu/hotplug, stop_machine: Fix stop_machine vs hotplug orderPeter Zijlstra2020-02-281-4/+9
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | [ Upstream commit 45178ac0cea853fe0e405bf11e101bdebea57b15 ] Paul reported a very sporadic, rcutorture induced, workqueue failure. When the planets align, the workqueue rescuer's self-migrate fails and then triggers a WARN for running a work on the wrong CPU. Tejun then figured that set_cpus_allowed_ptr()'s stop_one_cpu() call could be ignored! When stopper->enabled is false, stop_machine will insta complete the work, without actually doing the work. Worse, it will not WARN about this (we really should fix this). It turns out there is a small window where a freshly online'ed CPU is marked 'online' but doesn't yet have the stopper task running: BP AP bringup_cpu() __cpu_up(cpu, idle) --> start_secondary() ... cpu_startup_entry() bringup_wait_for_ap() wait_for_ap_thread() <-- cpuhp_online_idle() while (1) do_idle() ... available to run kthreads ... stop_machine_unpark() stopper->enable = true; Close this by moving the stop_machine_unpark() into cpuhp_online_idle(), such that the stopper thread is ready before we start the idle loop and schedule. Reported-by: "Paul E. McKenney" <paulmck@kernel.org> Debugged-by: Tejun Heo <tj@kernel.org> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Tested-by: "Paul E. McKenney" <paulmck@kernel.org> Signed-off-by: Sasha Levin <sashal@kernel.org>
* cpu/SMT: State SMT is disabled even with nosmt and without "=force"Borislav Petkov2019-11-251-0/+1
| | | | | | | | | | | | | | | | | | [ Upstream commit d0e7d14455d41163126afecd0fcce935463cc512 ] When booting with "nosmt=force" a message is issued into dmesg to confirm that SMT has been force-disabled but such a message is not issued when only "nosmt" is on the kernel command line. Fix that. Signed-off-by: Borislav Petkov <bp@suse.de> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Link: http://lkml.kernel.org/r/20181004172227.10094-1-bp@alien8.de Signed-off-by: Ingo Molnar <mingo@kernel.org> Signed-off-by: Sasha Levin <sashal@kernel.org>
* cpu/speculation: Uninline and export CPU mitigations helpersTyler Hicks2019-11-161-1/+26
| | | | | | | | | | | | | | | | | | | | commit 731dc9df975a5da21237a18c3384f811a7a41cc6 upstream. A kernel module may need to check the value of the "mitigations=" kernel command line parameter as part of its setup when the module needs to perform software mitigations for a CPU flaw. Uninline and export the helper functions surrounding the cpu_mitigations enum to allow for their usage from a module. Lastly, privatize the enum and cpu_mitigations variable since the value of cpu_mitigations can be checked with the exported helper functions. Signed-off-by: Tyler Hicks <tyhicks@canonical.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Ben Hutchings <ben@decadent.org.uk> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
* cpu/speculation: Warn on unsupported mitigations= parameterGeert Uytterhoeven2019-07-101-0/+3
| | | | | | | | | | | | | | | | | | | | | | | | | | | commit 1bf72720281770162c87990697eae1ba2f1d917a upstream. Currently, if the user specifies an unsupported mitigation strategy on the kernel command line, it will be ignored silently. The code will fall back to the default strategy, possibly leaving the system more vulnerable than expected. This may happen due to e.g. a simple typo, or, for a stable kernel release, because not all mitigation strategies have been backported. Inform the user by printing a message. Fixes: 98af8452945c5565 ("cpu/speculation: Add 'mitigations=' cmdline option") Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Acked-by: Josh Poimboeuf <jpoimboe@redhat.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Jiri Kosina <jkosina@suse.cz> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Cc: Ben Hutchings <ben@decadent.org.uk> Cc: stable@vger.kernel.org Link: https://lkml.kernel.org/r/20190516070935.22546-1-geert@linux-m68k.org Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
* x86/power: Fix 'nosmt' vs hibernation triple fault during resumeJiri Kosina2019-06-111-2/+2
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | commit ec527c318036a65a083ef68d8ba95789d2212246 upstream. As explained in 0cc3cd21657b ("cpu/hotplug: Boot HT siblings at least once") we always, no matter what, have to bring up x86 HT siblings during boot at least once in order to avoid first MCE bringing the system to its knees. That means that whenever 'nosmt' is supplied on the kernel command-line, all the HT siblings are as a result sitting in mwait or cpudile after going through the online-offline cycle at least once. This causes a serious issue though when a kernel, which saw 'nosmt' on its commandline, is going to perform resume from hibernation: if the resume from the hibernated image is successful, cr3 is flipped in order to point to the address space of the kernel that is being resumed, which in turn means that all the HT siblings are all of a sudden mwaiting on address which is no longer valid. That results in triple fault shortly after cr3 is switched, and machine reboots. Fix this by always waking up all the SMT siblings before initiating the 'restore from hibernation' process; this guarantees that all the HT siblings will be properly carried over to the resumed kernel waiting in resume_play_dead(), and acted upon accordingly afterwards, based on the target kernel configuration. Symmetricaly, the resumed kernel has to push the SMT siblings to mwait again in case it has SMT disabled; this means it has to online all the siblings when resuming (so that they come out of hlt) and offline them again to let them reach mwait. Cc: 4.19+ <stable@vger.kernel.org> # v4.19+ Debugged-by: Thomas Gleixner <tglx@linutronix.de> Fixes: 0cc3cd21657b ("cpu/hotplug: Boot HT siblings at least once") Signed-off-by: Jiri Kosina <jkosina@suse.cz> Acked-by: Pavel Machek <pavel@ucw.cz> Reviewed-by: Thomas Gleixner <tglx@linutronix.de> Reviewed-by: Josh Poimboeuf <jpoimboe@redhat.com> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
* cpu/speculation: Add 'mitigations=' cmdline optionJosh Poimboeuf2019-05-141-0/+15
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | commit 98af8452945c55652de68536afdde3b520fec429 upstream. Keeping track of the number of mitigations for all the CPU speculation bugs has become overwhelming for many users. It's getting more and more complicated to decide which mitigations are needed for a given architecture. Complicating matters is the fact that each arch tends to have its own custom way to mitigate the same vulnerability. Most users fall into a few basic categories: a) they want all mitigations off; b) they want all reasonable mitigations on, with SMT enabled even if it's vulnerable; or c) they want all reasonable mitigations on, with SMT disabled if vulnerable. Define a set of curated, arch-independent options, each of which is an aggregation of existing options: - mitigations=off: Disable all mitigations. - mitigations=auto: [default] Enable all the default mitigations, but leave SMT enabled, even if it's vulnerable. - mitigations=auto,nosmt: Enable all the default mitigations, disabling SMT if needed by a mitigation. Currently, these options are placeholders which don't actually do anything. They will be fleshed out in upcoming patches. Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Tested-by: Jiri Kosina <jkosina@suse.cz> (on x86) Reviewed-by: Jiri Kosina <jkosina@suse.cz> Cc: Borislav Petkov <bp@alien8.de> Cc: "H . Peter Anvin" <hpa@zytor.com> Cc: Andy Lutomirski <luto@kernel.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Jiri Kosina <jikos@kernel.org> Cc: Waiman Long <longman@redhat.com> Cc: Andrea Arcangeli <aarcange@redhat.com> Cc: Jon Masters <jcm@redhat.com> Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org> Cc: Paul Mackerras <paulus@samba.org> Cc: Michael Ellerman <mpe@ellerman.id.au> Cc: linuxppc-dev@lists.ozlabs.org Cc: Martin Schwidefsky <schwidefsky@de.ibm.com> Cc: Heiko Carstens <heiko.carstens@de.ibm.com> Cc: linux-s390@vger.kernel.org Cc: Catalin Marinas <catalin.marinas@arm.com> Cc: Will Deacon <will.deacon@arm.com> Cc: linux-arm-kernel@lists.infradead.org Cc: linux-arch@vger.kernel.org Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Cc: Tyler Hicks <tyhicks@canonical.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Randy Dunlap <rdunlap@infradead.org> Cc: Steven Price <steven.price@arm.com> Cc: Phil Auld <pauld@redhat.com> Link: https://lkml.kernel.org/r/b07a8ef9b7c5055c3a4637c87d07c296d5016fe0.1555085500.git.jpoimboe@redhat.com [bwh: Backported to 4.9: adjust filename] Signed-off-by: Ben Hutchings <ben@decadent.org.uk> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
* x86/speculation: Rework SMT state changeThomas Gleixner2019-05-141-6/+9
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | commit a74cfffb03b73d41e08f84c2e5c87dec0ce3db9f upstream. arch_smt_update() is only called when the sysfs SMT control knob is changed. This means that when SMT is enabled in the sysfs control knob the system is considered to have SMT active even if all siblings are offline. To allow finegrained control of the speculation mitigations, the actual SMT state is more interesting than the fact that siblings could be enabled. Rework the code, so arch_smt_update() is invoked from each individual CPU hotplug function, and simplify the update function while at it. Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Reviewed-by: Ingo Molnar <mingo@kernel.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Andy Lutomirski <luto@kernel.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Jiri Kosina <jkosina@suse.cz> Cc: Tom Lendacky <thomas.lendacky@amd.com> Cc: Josh Poimboeuf <jpoimboe@redhat.com> Cc: Andrea Arcangeli <aarcange@redhat.com> Cc: David Woodhouse <dwmw@amazon.co.uk> Cc: Tim Chen <tim.c.chen@linux.intel.com> Cc: Andi Kleen <ak@linux.intel.com> Cc: Dave Hansen <dave.hansen@intel.com> Cc: Casey Schaufler <casey.schaufler@intel.com> Cc: Asit Mallick <asit.k.mallick@intel.com> Cc: Arjan van de Ven <arjan@linux.intel.com> Cc: Jon Masters <jcm@redhat.com> Cc: Waiman Long <longman9394@gmail.com> Cc: Greg KH <gregkh@linuxfoundation.org> Cc: Dave Stewart <david.c.stewart@intel.com> Cc: Kees Cook <keescook@chromium.org> Link: https://lkml.kernel.org/r/20181125185004.521974984@linutronix.de [bwh: Backported to 4.9: adjust context] Signed-off-by: Ben Hutchings <ben@decadent.org.uk> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
* x86/speculation: Enable cross-hyperthread spectre v2 STIBP mitigationJiri Kosina2019-05-141-1/+10
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | commit 53c613fe6349994f023245519265999eed75957f upstream. STIBP is a feature provided by certain Intel ucodes / CPUs. This feature (once enabled) prevents cross-hyperthread control of decisions made by indirect branch predictors. Enable this feature if - the CPU is vulnerable to spectre v2 - the CPU supports SMT and has SMT siblings online - spectre_v2 mitigation autoselection is enabled (default) After some previous discussion, this leaves STIBP on all the time, as wrmsr on crossing kernel boundary is a no-no. This could perhaps later be a bit more optimized (like disabling it in NOHZ, experiment with disabling it in idle, etc) if needed. Note that the synchronization of the mask manipulation via newly added spec_ctrl_mutex is currently not strictly needed, as the only updater is already being serialized by cpu_add_remove_lock, but let's make this a little bit more future-proof. Signed-off-by: Jiri Kosina <jkosina@suse.cz> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Josh Poimboeuf <jpoimboe@redhat.com> Cc: Andrea Arcangeli <aarcange@redhat.com> Cc: "WoodhouseDavid" <dwmw@amazon.co.uk> Cc: Andi Kleen <ak@linux.intel.com> Cc: Tim Chen <tim.c.chen@linux.intel.com> Cc: "SchauflerCasey" <casey.schaufler@intel.com> Link: https://lkml.kernel.org/r/nycvar.YFH.7.76.1809251438240.15880@cbobk.fhfr.pm Signed-off-by: Ben Hutchings <ben@decadent.org.uk> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
* cpu/hotplug: Prevent crash when CPU bringup fails on CONFIG_HOTPLUG_CPU=nThomas Gleixner2019-04-031-2/+18
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | commit 206b92353c839c0b27a0b9bec24195f93fd6cf7a upstream. Tianyu reported a crash in a CPU hotplug teardown callback when booting a kernel which has CONFIG_HOTPLUG_CPU disabled with the 'nosmt' boot parameter. It turns out that the SMP=y CONFIG_HOTPLUG_CPU=n case has been broken forever in case that a bringup callback fails. Unfortunately this issue was not recognized when the CPU hotplug code was reworked, so the shortcoming just stayed in place. When a bringup callback fails, the CPU hotplug code rolls back the operation and takes the CPU offline. The 'nosmt' command line argument uses a bringup failure to abort the bringup of SMT sibling CPUs. This partial bringup is required due to the MCE misdesign on Intel CPUs. With CONFIG_HOTPLUG_CPU=y the rollback works perfectly fine, but CONFIG_HOTPLUG_CPU=n lacks essential mechanisms to exercise the low level teardown of a CPU including the synchronizations in various facilities like RCU, NOHZ and others. As a consequence the teardown callbacks which must be executed on the outgoing CPU within stop machine with interrupts disabled are executed on the control CPU in interrupt enabled and preemptible context causing the kernel to crash and burn. The pre state machine code has a different failure mode which is more subtle and resulting in a less obvious use after free crash because the control side frees resources which are still in use by the undead CPU. But this is not a x86 only problem. Any architecture which supports the SMP=y HOTPLUG_CPU=n combination suffers from the same issue. It's just less likely to be triggered because in 99.99999% of the cases all bringup callbacks succeed. The easy solution of making HOTPLUG_CPU mandatory for SMP is not working on all architectures as the following architectures have either no hotplug support at all or not all subarchitectures support it: alpha, arc, hexagon, openrisc, riscv, sparc (32bit), mips (partial). Crashing the kernel in such a situation is not an acceptable state either. Implement a minimal rollback variant by limiting the teardown to the point where all regular teardown callbacks have been invoked and leave the CPU in the 'dead' idle state. This has the following consequences: - the CPU is brought down to the point where the stop_machine takedown would happen. - the CPU stays there forever and is idle - The CPU is cleared in the CPU active mask, but not in the CPU online mask which is a legit state. - Interrupts are not forced away from the CPU - All facilities which only look at online mask would still see it, but that is the case during normal hotplug/unplug operations as well. It's just a (way) longer time frame. This will expose issues, which haven't been exposed before or only seldom, because now the normally transient state of being non active but online is a permanent state. In testing this exposed already an issue vs. work queues where the vmstat code schedules work on the almost dead CPU which ends up in an unbound workqueue and triggers 'preemtible context' warnings. This is not a problem of this change, it merily exposes an already existing issue. Still this is better than crashing fully without a chance to debug it. This is mainly thought as workaround for those architectures which do not support HOTPLUG_CPU. All others should enforce HOTPLUG_CPU for SMP. Fixes: 2e1a3483ce74 ("cpu/hotplug: Split out the state walk into functions") Reported-by: Tianyu Lan <Tianyu.Lan@microsoft.com> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Tested-by: Tianyu Lan <Tianyu.Lan@microsoft.com> Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Cc: Konrad Wilk <konrad.wilk@oracle.com> Cc: Josh Poimboeuf <jpoimboe@redhat.com> Cc: Mukesh Ojha <mojha@codeaurora.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Jiri Kosina <jkosina@suse.cz> Cc: Rik van Riel <riel@surriel.com> Cc: Andy Lutomirski <luto@kernel.org> Cc: Micheal Kelley <michael.h.kelley@microsoft.com> Cc: "K. Y. Srinivasan" <kys@microsoft.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Borislav Petkov <bp@alien8.de> Cc: K. Y. Srinivasan <kys@microsoft.com> Cc: stable@vger.kernel.org Link: https://lkml.kernel.org/r/20190326163811.503390616@linutronix.de Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
* Revert "x86/speculation: Enable cross-hyperthread spectre v2 STIBP mitigation"Greg Kroah-Hartman2018-11-231-10/+1
| | | | | | | | | | | | | | | | | | | | | This reverts commit 66fe51cb35d91d75a67ec8a38caf03da95e8c191 which is commit 53c613fe6349994f023245519265999eed75957f upstream. It's not ready for the stable trees as there are major slowdowns involved with this patch. Reported-by: Jiri Kosina <jkosina@suse.cz> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Josh Poimboeuf <jpoimboe@redhat.com> Cc: Andrea Arcangeli <aarcange@redhat.com> Cc: "WoodhouseDavid" <dwmw@amazon.co.uk> Cc: Andi Kleen <ak@linux.intel.com> Cc: Tim Chen <tim.c.chen@linux.intel.com> Cc: "SchauflerCasey" <casey.schaufler@intel.com> Cc: Rainer Fiebig <jrf@mailbox.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
* x86/speculation: Enable cross-hyperthread spectre v2 STIBP mitigationJiri Kosina2018-11-131-1/+10
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | commit 53c613fe6349994f023245519265999eed75957f upstream. STIBP is a feature provided by certain Intel ucodes / CPUs. This feature (once enabled) prevents cross-hyperthread control of decisions made by indirect branch predictors. Enable this feature if - the CPU is vulnerable to spectre v2 - the CPU supports SMT and has SMT siblings online - spectre_v2 mitigation autoselection is enabled (default) After some previous discussion, this leaves STIBP on all the time, as wrmsr on crossing kernel boundary is a no-no. This could perhaps later be a bit more optimized (like disabling it in NOHZ, experiment with disabling it in idle, etc) if needed. Note that the synchronization of the mask manipulation via newly added spec_ctrl_mutex is currently not strictly needed, as the only updater is already being serialized by cpu_add_remove_lock, but let's make this a little bit more future-proof. Signed-off-by: Jiri Kosina <jkosina@suse.cz> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Josh Poimboeuf <jpoimboe@redhat.com> Cc: Andrea Arcangeli <aarcange@redhat.com> Cc: "WoodhouseDavid" <dwmw@amazon.co.uk> Cc: Andi Kleen <ak@linux.intel.com> Cc: Tim Chen <tim.c.chen@linux.intel.com> Cc: "SchauflerCasey" <casey.schaufler@intel.com> Cc: stable@vger.kernel.org Link: https://lkml.kernel.org/r/nycvar.YFH.7.76.1809251438240.15880@cbobk.fhfr.pm Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
* cpu/hotplug: Non-SMP machines do not make use of booted_onceAbel Vesa2018-08-151-0/+2
| | | | | | | | | | | | | | | | | | | | commit 269777aa530f3438ec1781586cdac0b5fe47b061 upstream. Commit 0cc3cd21657b ("cpu/hotplug: Boot HT siblings at least once") breaks non-SMP builds. [ I suspect the 'bool' fields should just be made to be bitfields and be exposed regardless of configuration, but that's a separate cleanup that I'll leave to the owners of this file for later. - Linus ] Fixes: 0cc3cd21657b ("cpu/hotplug: Boot HT siblings at least once") Cc: Dave Hansen <dave.hansen@intel.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Tony Luck <tony.luck@intel.com> Signed-off-by: Abel Vesa <abelvesa@linux.com> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
* cpu/hotplug: Fix SMT supported evaluationThomas Gleixner2018-08-151-13/+28
| | | | | | | | | | | | | | | | | | | | | | | | | commit bc2d8d262cba5736332cbc866acb11b1c5748aa9 upstream Josh reported that the late SMT evaluation in cpu_smt_state_init() sets cpu_smt_control to CPU_SMT_NOT_SUPPORTED in case that 'nosmt' was supplied on the kernel command line as it cannot differentiate between SMT disabled by BIOS and SMT soft disable via 'nosmt'. That wreckages the state and makes the sysfs interface unusable. Rework this so that during bringup of the non boot CPUs the availability of SMT is determined in cpu_smt_allowed(). If a newly booted CPU is not a 'primary' thread then set the local cpu_smt_available marker and evaluate this explicitely right after the initial SMP bringup has finished. SMT evaulation on x86 is a trainwreck as the firmware has all the information _before_ booting the kernel, but there is no interface to query it. Fixes: 73d5e2b47264 ("cpu/hotplug: detect SMT disabled by BIOS") Reported-by: Josh Poimboeuf <jpoimboe@redhat.com> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: David Woodhouse <dwmw@amazon.co.uk> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
* cpu/hotplug: detect SMT disabled by BIOSJosh Poimboeuf2018-08-151-0/+9
| | | | | | | | | | | | | | | | | | | | | commit 73d5e2b472640b1fcdb61ae8be389912ef211bda upstream If SMT is disabled in BIOS, the CPU code doesn't properly detect it. The /sys/devices/system/cpu/smt/control file shows 'on', and the 'l1tf' vulnerabilities file shows SMT as vulnerable. Fix it by forcing 'cpu_smt_control' to CPU_SMT_NOT_SUPPORTED in such a case. Unfortunately the detection can only be done after bringing all the CPUs online, so we have to overwrite any previous writes to the variable. Reported-by: Joe Mario <jmario@redhat.com> Tested-by: Jiri Kosina <jkosina@suse.cz> Fixes: f048c399e0f7 ("x86/topology: Provide topology_smt_supported()") Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com> Signed-off-by: Peter Zijlstra <peterz@infradead.org> Signed-off-by: David Woodhouse <dwmw@amazon.co.uk> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
* cpu/hotplug: Set CPU_SMT_NOT_SUPPORTED earlyThomas Gleixner2018-08-151-3/+10
| | | | | | | | | | | | | | | | | | | | | commit fee0aede6f4739c87179eca76136f83210953b86 upstream The CPU_SMT_NOT_SUPPORTED state is set (if the processor does not support SMT) when the sysfs SMT control file is initialized. That was fine so far as this was only required to make the output of the control file correct and to prevent writes in that case. With the upcoming l1tf command line parameter, this needs to be set up before the L1TF mitigation selection and command line parsing happens. Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Tested-by: Jiri Kosina <jkosina@suse.cz> Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Reviewed-by: Josh Poimboeuf <jpoimboe@redhat.com> Link: https://lkml.kernel.org/r/20180713142323.121795971@linutronix.de Signed-off-by: David Woodhouse <dwmw@amazon.co.uk> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
* cpu/hotplug: Expose SMT control init functionJiri Kosina2018-08-151-3/+13
| | | | | | | | | | | | | | | | | | | | | commit 8e1b706b6e819bed215c0db16345568864660393 upstream The L1TF mitigation will gain a commend line parameter which allows to set a combination of hypervisor mitigation and SMT control. Expose cpu_smt_disable() so the command line parser can tweak SMT settings. [ tglx: Split out of larger patch and made it preserve an already existing force off state ] Signed-off-by: Jiri Kosina <jkosina@suse.cz> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Tested-by: Jiri Kosina <jkosina@suse.cz> Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Reviewed-by: Josh Poimboeuf <jpoimboe@redhat.com> Link: https://lkml.kernel.org/r/20180713142323.039715135@linutronix.de Signed-off-by: David Woodhouse <dwmw@amazon.co.uk> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
* cpu/hotplug: Online siblings when SMT control is turned onThomas Gleixner2018-08-151-2/+24
| | | | | | | | | | | | | | commit 215af5499d9e2b55f111d2431ea20218115f29b3 upstream Writing 'off' to /sys/devices/system/cpu/smt/control offlines all SMT siblings. Writing 'on' merily enables the abilify to online them, but does not online them automatically. Make 'on' more useful by onlining all offline siblings. Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: David Woodhouse <dwmw@amazon.co.uk> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
* x86/KVM: Warn user if KVM is loaded SMT and L1TF CPU bug being presentKonrad Rzeszutek Wilk2018-08-151-0/+1
| | | | | | | | | | | | | | | | | | | | | | | | | commit 26acfb666a473d960f0fd971fe68f3e3ad16c70b upstream If the L1TF CPU bug is present we allow the KVM module to be loaded as the major of users that use Linux and KVM have trusted guests and do not want a broken setup. Cloud vendors are the ones that are uncomfortable with CVE 2018-3620 and as such they are the ones that should set nosmt to one. Setting 'nosmt' means that the system administrator also needs to disable SMT (Hyper-threading) in the BIOS, or via the 'nosmt' command line parameter, or via the /sys/devices/system/cpu/smt/control. See commit 05736e4ac13c ("cpu/hotplug: Provide knobs to control SMT"). Other mitigations are to use task affinity, cpu sets, interrupt binding, etc - anything to make sure that _only_ the same guests vCPUs are running on sibling threads. Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: David Woodhouse <dwmw@amazon.co.uk> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
* cpu/hotplug: Boot HT siblings at least onceThomas Gleixner2018-08-151-24/+48
| | | | | | | | | | | | | | | | | | | | | commit 0cc3cd21657be04cb0559fe8063f2130493f92cf upstream Due to the way Machine Check Exceptions work on X86 hyperthreads it's required to boot up _all_ logical cores at least once in order to set the CR4.MCE bit. So instead of ignoring the sibling threads right away, let them boot up once so they can configure themselves. After they came out of the initial boot stage check whether its a "secondary" sibling and cancel the operation which puts the CPU back into offline state. [dwmw2: Backport to 4.9] Reported-by: Dave Hansen <dave.hansen@intel.com> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Tested-by: Tony Luck <tony.luck@intel.com> Signed-off-by: David Woodhouse <dwmw@amazon.co.uk> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
* cpu/hotplug: Provide knobs to control SMTThomas Gleixner2018-08-151-0/+170
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | commit 05736e4ac13c08a4a9b1ef2de26dd31a32cbee57 upstream Provide a command line and a sysfs knob to control SMT. The command line options are: 'nosmt': Enumerate secondary threads, but do not online them 'nosmt=force': Ignore secondary threads completely during enumeration via MP table and ACPI/MADT. The sysfs control file has the following states (read/write): 'on': SMT is enabled. Secondary threads can be freely onlined 'off': SMT is disabled. Secondary threads, even if enumerated cannot be onlined 'forceoff': SMT is permanentely disabled. Writes to the control file are rejected. 'notsupported': SMT is not supported by the CPU The command line option 'nosmt' sets the sysfs control to 'off'. This can be changed to 'on' to reenable SMT during runtime. The command line option 'nosmt=force' sets the sysfs control to 'forceoff'. This cannot be changed during runtime. When SMT is 'on' and the control file is changed to 'off' then all online secondary threads are offlined and attempts to online a secondary thread later on are rejected. When SMT is 'off' and the control file is changed to 'on' then secondary threads can be onlined again. The 'off' -> 'on' transition does not automatically online the secondary threads. When the control file is set to 'forceoff', the behaviour is the same as setting it to 'off', but the operation is irreversible and later writes to the control file are rejected. When the control status is 'notsupported' then writes to the control file are rejected. Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Reviewed-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com> Acked-by: Ingo Molnar <mingo@kernel.org> Signed-off-by: David Woodhouse <dwmw@amazon.co.uk> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
* cpu/hotplug: Split do_cpu_down()Thomas Gleixner2018-08-151-9/+8
| | | | | | | | | | | | | | | commit cc1fe215e1efa406b03aa4389e6269b61342dec5 upstream Split out the inner workings of do_cpu_down() to allow reuse of that function for the upcoming SMT disabling mechanism. No functional change. Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Reviewed-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com> Acked-by: Ingo Molnar <mingo@kernel.org> Signed-off-by: David Woodhouse <dwmw@amazon.co.uk> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
* cpu/hotplug: Make bringup/teardown of smp threads symmetricThomas Gleixner2018-08-151-2/+1
| | | | | | | | | | | | | | | commit c4de65696d865c225fda3b9913b31284ea65ea96 upstream The asymmetry caused a warning to trigger if the bootup was stopped in state CPUHP_AP_ONLINE_IDLE. The warning no longer triggers as kthread_park() can now be invoked on already or still parked threads. But there is still no reason to have this be asymmetric. Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Reviewed-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com> Acked-by: Ingo Molnar <mingo@kernel.org> Signed-off-by: David Woodhouse <dwmw@amazon.co.uk> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
* init: rename and re-order boot_cpu_state_init()Linus Torvalds2018-08-151-1/+1
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | commit b5b1404d0815894de0690de8a1ab58269e56eae6 upstream. This is purely a preparatory patch for upcoming changes during the 4.19 merge window. We have a function called "boot_cpu_state_init()" that isn't really about the bootup cpu state: that is done much earlier by the similarly named "boot_cpu_init()" (note lack of "state" in name). This function initializes some hotplug CPU state, and needs to run after the percpu data has been properly initialized. It even has a comment to that effect. Except it _doesn't_ actually run after the percpu data has been properly initialized. On x86 it happens to do that, but on at least arm and arm64, the percpu base pointers are initialized by the arch-specific 'smp_prepare_boot_cpu()' hook, which ran _after_ boot_cpu_state_init(). This had some unexpected results, and in particular we have a patch pending for the merge window that did the obvious cleanup of using 'this_cpu_write()' in the cpu hotplug init code: - per_cpu_ptr(&cpuhp_state, smp_processor_id())->state = CPUHP_ONLINE; + this_cpu_write(cpuhp_state.state, CPUHP_ONLINE); which is obviously the right thing to do. Except because of the ordering issue, it actually failed miserably and unexpectedly on arm64. So this just fixes the ordering, and changes the name of the function to be 'boot_cpu_hotplug_init()' to make it obvious that it's about cpu hotplug state, because the core CPU state was supposed to have already been done earlier. Marked for stable, since the (not yet merged) patch that will show this problem is marked for stable. Reported-by: Vlastimil Babka <vbabka@suse.cz> Reported-by: Mian Yousaf Kaukab <yousaf.kaukab@suse.com> Suggested-by: Catalin Marinas <catalin.marinas@arm.com> Acked-by: Thomas Gleixner <tglx@linutronix.de> Cc: Will Deacon <will.deacon@arm.com> Cc: stable@kernel.org Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
* cpuhotplug: Link lock stacks for hotplug callbacksThomas Gleixner2018-04-131-0/+13
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | [ Upstream commit 49dfe2a6779717d9c18395684ee31bdc98b22e53 ] The CPU hotplug callbacks are not covered by lockdep versus the cpu hotplug rwsem. CPU0 CPU1 cpuhp_setup_state(STATE, startup, teardown); cpus_read_lock(); invoke_callback_on_ap(); kick_hotplug_thread(ap); wait_for_completion(); hotplug_thread_fn() lock(m); do_stuff(); unlock(m); Lockdep does not know about this dependency and will not trigger on the following code sequence: lock(m); cpus_read_lock(); Add a lockdep map and connect the initiators lock chain with the hotplug thread lock chain, so potential deadlocks can be detected. Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Tested-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Acked-by: Ingo Molnar <mingo@kernel.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Sebastian Siewior <bigeasy@linutronix.de> Cc: Steven Rostedt <rostedt@goodmis.org> Link: http://lkml.kernel.org/r/20170524081549.709375845@linutronix.de Signed-off-by: Sasha Levin <alexander.levin@microsoft.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
* timers: Reinitialize per cpu bases on hotplugThomas Gleixner2018-01-021-2/+2
| | | | | | | | | | | | | | | | | | | | | | | | | commit 26456f87aca7157c057de65c9414b37f1ab881d1 upstream. The timer wheel bases are not (re)initialized on CPU hotplug. That leaves them with a potentially stale clk and next_expiry valuem, which can cause trouble then the CPU is plugged. Add a prepare callback which forwards the clock, sets next_expiry to far in the future and reset the control flags to a known state. Set base->must_forward_clk so the first timer which is queued will try to forward the clock to current jiffies. Fixes: 500462a9de65 ("timers: Switch to a non-cascading wheel") Reported-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Frederic Weisbecker <fweisbec@gmail.com> Cc: Sebastian Siewior <bigeasy@linutronix.de> Cc: Anna-Maria Gleixner <anna-maria@linutronix.de> Link: https://lkml.kernel.org/r/alpine.DEB.2.20.1712272152200.2431@nanos Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
* smp/hotplug: Move step CPUHP_AP_SMPCFD_DYING to the correct placeLai Jiangshan2017-12-141-5/+5
| | | | | | | | | | | | | | | | | | | | | | | | | | commit 46febd37f9c758b05cd25feae8512f22584742fe upstream. Commit 31487f8328f2 ("smp/cfd: Convert core to hotplug state machine") accidently put this step on the wrong place. The step should be at the cpuhp_ap_states[] rather than the cpuhp_bp_states[]. grep smpcfd /sys/devices/system/cpu/hotplug/states 40: smpcfd:prepare 129: smpcfd:dying "smpcfd:dying" was missing before. So was the invocation of the function smpcfd_dying_cpu(). Fixes: 31487f8328f2 ("smp/cfd: Convert core to hotplug state machine") Signed-off-by: Lai Jiangshan <jiangshanlai@gmail.com> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Richard Weinberger <richard@nod.at> Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de> Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com> Link: https://lkml.kernel.org/r/20171128131954.81229-1-jiangshanlai@gmail.com Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
* smp/hotplug: Replace BUG_ON and react usefulThomas Gleixner2017-08-061-1/+2
| | | | | | | | | | | | | | | | | | commit dea1d0f5f1284e3defee4b8484d9fc230686cd42 upstream. The move of the unpark functions to the control thread moved the BUG_ON() there as well. While it made some sense in the idle thread of the upcoming CPU, it's bogus to crash the control thread on the already online CPU, especially as the function has a return value and the callsite is prepared to handle an error return. Replace it with a WARN_ON_ONCE() and return a proper error code. Fixes: 9cd4f1a4e7a8 ("smp/hotplug: Move unparking of percpu threads to the control CPU") Rightfully-ranted-at-by: Linux Torvalds <torvalds@linux-foundation.org> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
* smp/hotplug: Move unparking of percpu threads to the control CPUThomas Gleixner2017-08-061-18/+19
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | commit 9cd4f1a4e7a858849e889a081a99adff83e08e4c upstream. Vikram reported the following backtrace: BUG: scheduling while atomic: swapper/7/0/0x00000002 CPU: 7 PID: 0 Comm: swapper/7 Not tainted 4.9.32-perf+ #680 schedule schedule_hrtimeout_range_clock schedule_hrtimeout wait_task_inactive __kthread_bind_mask __kthread_bind __kthread_unpark kthread_unpark cpuhp_online_idle cpu_startup_entry secondary_start_kernel He analyzed correctly that a parked cpu hotplug thread of an offlined CPU was still on the runqueue when the CPU came back online and tried to unpark it. This causes the thread which invoked kthread_unpark() to call wait_task_inactive() and subsequently schedule() with preemption disabled. His proposed workaround was to "make sure" that a parked thread has scheduled out when the CPU goes offline, so the situation cannot happen. But that's still wrong because the root cause is not the fact that the percpu thread is still on the runqueue and neither that preemption is disabled, which could be simply solved by enabling preemption before calling kthread_unpark(). The real issue is that the calling thread is the idle task of the upcoming CPU, which is not supposed to call anything which might sleep. The moron, who wrote that code, missed completely that kthread_unpark() might end up in schedule(). The solution is simpler than expected. The thread which controls the hotplug operation is waiting for the CPU to call complete() on the hotplug state completion. So the idle task of the upcoming CPU can set its state to CPUHP_AP_ONLINE_IDLE and invoke complete(). This in turn wakes the control task on a different CPU, which then can safely do the unpark and kick the now unparked hotplug thread of the upcoming CPU to complete the bringup to the final target state. Control CPU AP bringup_cpu(); __cpu_up() ------------> bringup_ap(); bringup_wait_for_ap() wait_for_completion(); cpuhp_online_idle(); <------------ complete(); unpark(AP->stopper); unpark(AP->hotplugthread); while(1) do_idle(); kick(AP->hotplugthread); wait_for_completion(); hotplug_thread() run_online_callbacks(); complete(); Fixes: 8df3e07e7f21 ("cpu/hotplug: Let upcoming cpu bring itself fully up") Reported-by: Vikram Mulukutla <markivx@codeaurora.org> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Acked-by: Peter Zijlstra <peterz@infradead.org> Cc: Sebastian Sewior <bigeasy@linutronix.de> Cc: Rusty Russell <rusty@rustcorp.com.au> Cc: Tejun Heo <tj@kernel.org> Cc: Andrew Morton <akpm@linux-foundation.org> Link: http://lkml.kernel.org/r/alpine.DEB.2.20.1707042218020.2131@nanos Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
* cpu/hotplug: Drop the device lock on errorSebastian Andrzej Siewior2017-06-141-2/+2
| | | | | | | | | | | | | | | | | | | | | | | | | commit 40da1b11f01e43aad1aa6cea64681b6125e8a2a7 upstream. If a custom CPU target is specified and that one is not available _or_ can't be interrupted then the code returns to userland without dropping a lock as notices by lockdep: |echo 133 > /sys/devices/system/cpu/cpu7/hotplug/target | ================================================ | [ BUG: lock held when returning to user space! ] | ------------------------------------------------ | bash/503 is leaving the kernel with locks still held! | 1 lock held by bash/503: | #0: (device_hotplug_lock){+.+...}, at: [<ffffffff815b5650>] lock_device_hotplug_sysfs+0x10/0x40 So release the lock then. Fixes: 757c989b9994 ("cpu/hotplug: Make target state writeable") Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Link: http://lkml.kernel.org/r/20170602142714.3ogo25f2wbq6fjpj@linutronix.de Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
* cpu/hotplug: Serialize callback invocations properSebastian Andrzej Siewior2017-05-081-8/+9
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | commit dc434e056fe1dada20df7ba07f32739d3a701adf upstream. The setup/remove_state/instance() functions in the hotplug core code are serialized against concurrent CPU hotplug, but unfortunately not serialized against themself. As a consequence a concurrent invocation of these function results in corruption of the callback machinery because two instances try to invoke callbacks on remote cpus at the same time. This results in missing callback invocations and initiator threads waiting forever on the completion. The obvious solution to replace get_cpu_online() with cpu_hotplug_begin() is not possible because at least one callsite calls into these functions from a get_online_cpu() locked region. Extend the protection scope of the cpuhp_state_mutex from solely protecting the state arrays to cover the callback invocation machinery as well. Fixes: 5b7aa87e0482 ("cpu/hotplug: Implement setup/removal interface") Reported-and-tested-by: Bart Van Assche <Bart.VanAssche@sandisk.com> Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de> Cc: hpa@zytor.com Cc: mingo@kernel.org Cc: akpm@linux-foundation.org Cc: torvalds@linux-foundation.org Link: http://lkml.kernel.org/r/20170314150645.g4tdyoszlcbajmna@linutronix.de Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
* hotplug: Make register and unregister notifier API symmetricMichal Hocko2017-01-061-1/+1
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | commit 777c6e0daebb3fcefbbd6f620410a946b07ef6d0 upstream. Yu Zhao has noticed that __unregister_cpu_notifier only unregisters its notifiers when HOTPLUG_CPU=y while the registration might succeed even when HOTPLUG_CPU=n if MODULE is enabled. This means that e.g. zswap might keep a stale notifier on the list on the manual clean up during the pool tear down and thus corrupt the list. Resulting in the following [ 144.964346] BUG: unable to handle kernel paging request at ffff880658a2be78 [ 144.971337] IP: [<ffffffffa290b00b>] raw_notifier_chain_register+0x1b/0x40 <snipped> [ 145.122628] Call Trace: [ 145.125086] [<ffffffffa28e5cf8>] __register_cpu_notifier+0x18/0x20 [ 145.131350] [<ffffffffa2a5dd73>] zswap_pool_create+0x273/0x400 [ 145.137268] [<ffffffffa2a5e0fc>] __zswap_param_set+0x1fc/0x300 [ 145.143188] [<ffffffffa2944c1d>] ? trace_hardirqs_on+0xd/0x10 [ 145.149018] [<ffffffffa2908798>] ? kernel_param_lock+0x28/0x30 [ 145.154940] [<ffffffffa2a3e8cf>] ? __might_fault+0x4f/0xa0 [ 145.160511] [<ffffffffa2a5e237>] zswap_compressor_param_set+0x17/0x20 [ 145.167035] [<ffffffffa2908d3c>] param_attr_store+0x5c/0xb0 [ 145.172694] [<ffffffffa290848d>] module_attr_store+0x1d/0x30 [ 145.178443] [<ffffffffa2b2b41f>] sysfs_kf_write+0x4f/0x70 [ 145.183925] [<ffffffffa2b2a5b9>] kernfs_fop_write+0x149/0x180 [ 145.189761] [<ffffffffa2a99248>] __vfs_write+0x18/0x40 [ 145.194982] [<ffffffffa2a9a412>] vfs_write+0xb2/0x1a0 [ 145.200122] [<ffffffffa2a9a732>] SyS_write+0x52/0xa0 [ 145.205177] [<ffffffffa2ff4d97>] entry_SYSCALL_64_fastpath+0x12/0x17 This can be even triggered manually by changing /sys/module/zswap/parameters/compressor multiple times. Fix this issue by making unregister APIs symmetric to the register so there are no surprises. Fixes: 47e627bc8c9a ("[PATCH] hotplug: Allow modules to use the cpu hotplug notifiers even if !CONFIG_HOTPLUG_CPU") Reported-and-tested-by: Yu Zhao <yuzhao@google.com> Signed-off-by: Michal Hocko <mhocko@suse.com> Cc: linux-mm@kvack.org Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Dan Streetman <ddstreet@ieee.org> Link: http://lkml.kernel.org/r/20161207135438.4310-1-mhocko@kernel.org Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
* cpu/hotplug: Use distinct name for cpu_hotplug.dep_mapJoonas Lahtinen2016-10-161-1/+1
| | | | | | | | | | | | | | | | | | Use distinctive name for cpu_hotplug.dep_map to avoid the actual cpu_hotplug.lock appearing as cpu_hotplug.lock#2 in lockdep splats. Signed-off-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com> Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk> Acked-by: Gautham R. Shenoy <ego@linux.vnet.ibm.com> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Daniel Vetter <daniel.vetter@ffwll.ch> Cc: Gautham R . Shenoy <ego@linux.vnet.ibm.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: intel-gfx@lists.freedesktop.org Cc: trivial@kernel.org Signed-off-by: Ingo Molnar <mingo@kernel.org>
* Merge branch 'smp-hotplug-for-linus' of ↵Linus Torvalds2016-10-031-181/+331
|\ | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip Pull CPU hotplug updates from Thomas Gleixner: "Yet another batch of cpu hotplug core updates and conversions: - Provide core infrastructure for multi instance drivers so the drivers do not have to keep custom lists. - Convert custom lists to the new infrastructure. The block-mq custom list conversion comes through the block tree and makes the diffstat tip over to more lines removed than added. - Handle unbalanced hotplug enable/disable calls more gracefully. - Remove the obsolete CPU_STARTING/DYING notifier support. - Convert another batch of notifier users. The relayfs changes which conflicted with the conversion have been shipped to me by Andrew. The remaining lot is targeted for 4.10 so that we finally can remove the rest of the notifiers" * 'smp-hotplug-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (46 commits) cpufreq: Fix up conversion to hotplug state machine blk/mq: Reserve hotplug states for block multiqueue x86/apic/uv: Convert to hotplug state machine s390/mm/pfault: Convert to hotplug state machine mips/loongson/smp: Convert to hotplug state machine mips/octeon/smp: Convert to hotplug state machine fault-injection/cpu: Convert to hotplug state machine padata: Convert to hotplug state machine cpufreq: Convert to hotplug state machine ACPI/processor: Convert to hotplug state machine virtio scsi: Convert to hotplug state machine oprofile/timer: Convert to hotplug state machine block/softirq: Convert to hotplug state machine lib/irq_poll: Convert to hotplug state machine x86/microcode: Convert to hotplug state machine sh/SH-X3 SMP: Convert to hotplug state machine ia64/mca: Convert to hotplug state machine ARM/OMAP/wakeupgen: Convert to hotplug state machine ARM/shmobile: Convert to hotplug state machine arm64/FP/SIMD: Convert to hotplug state machine ...
| * slab: Convert to hotplug state machineSebastian Andrzej Siewior2016-09-061-0/+6
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Install the callbacks via the state machine. Signed-off-by: Richard Weinberger <richard@nod.at> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de> Reviewed-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Pekka Enberg <penberg@kernel.org> Cc: linux-mm@kvack.org Cc: rt@linutronix.de Cc: David Rientjes <rientjes@google.com> Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Christoph Lameter <cl@linux.com> Link: http://lkml.kernel.org/r/20160823125319.abeapfjapf2kfezp@linutronix.de Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
| * relayfs: Convert to hotplug state machineRichard Weinberger2016-09-061-0/+6
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Install the callbacks via the state machine. They are installed at run time but relay_prepare_cpu() does not need to be invoked by the boot CPU because relay_open() was not yet invoked and there are no pools that need to be created. Signed-off-by: Richard Weinberger <richard@nod.at> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de> Reviewed-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de> Cc: Peter Zijlstra <peterz@infradead.org> Cc: rt@linutronix.de Cc: Andrew Morton <akpm@linux-foundation.org> Link: http://lkml.kernel.org/r/20160818125731.27256-3-bigeasy@linutronix.de Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
| * cpu/hotplug: Remove CPU_STARTING and CPU_DYING notifierThomas Gleixner2016-09-061-28/+2
| | | | | | | | | | | | | | | | | | | | | | | | | | All users are converted to state machine, remove CPU_STARTING and the corresponding CPU_DYING. Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de> Cc: Peter Zijlstra <peterz@infradead.org> Cc: rt@linutronix.de Link: http://lkml.kernel.org/r/20160818125731.27256-2-bigeasy@linutronix.de Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
| * cpu/hotplug: Make state names consistentThomas Gleixner2016-09-061-7/+7
| | | | | | | | | | | | | | We should have all names in the scheme "[subsys/]facility:state]". Fix the core to comply. Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
| * cpu/hotplug: Replace anon unionThomas Gleixner2016-09-051-71/+74
| | | | | | | | | | | | | | | | | | | | | | | | | | | | Some compilers are unhappy with the anon union in the state array. Replace it with a named union. While at it align the state array initializers proper and add the missing name tags. Fixes: cf392d10b69e "cpu/hotplug: Add multi instance support" Reported-by: Ingo Molnar <mingo@kernel.org> Reported-by: Fenguang Wu <fengguang.wu@intel.com> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Cc: rt@linutronix.de
| * cpu/hotplug: Handle unbalanced hotplug enable/disableLianwei Wang2016-09-021-2/+9
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | When cpu_hotplug_enable() is called unbalanced w/o a preceeding cpu_hotplug_disable() the code emits a warning, but happily decrements the disabled counter. This causes the next operations to malfunction. Prevent the decrement and just emit a warning. Signed-off-by: Lianwei Wang <lianwei.wang@gmail.com> Cc: peterz@infradead.org Cc: linux-pm@vger.kernel.org Cc: oleg@redhat.com Link: http://lkml.kernel.org/r/1465541008-12476-1-git-send-email-lianwei.wang@gmail.com Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
| * cpu/hotplug: Add multi instance supportThomas Gleixner2016-09-021-35/+183
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | This patch adds the ability for a given state to have multiple instances. Until now all states have a single instance and the startup / teardown callback use global variables. A few drivers need to perform a the same callbacks on multiple "instances". Currently we have three drivers in tree which all have a global list which they iterate over. With multi instance they support don't need their private list and the functionality has been moved into core code. Plus we hold the hotplug lock in core so no cpus comes/goes while instances are registered and we do rollback in error case :) Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de> Cc: Mark Rutland <mark.rutland@arm.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Will Deacon <will.deacon@arm.com> Cc: rt@linutronix.de Link: http://lkml.kernel.org/r/1471024183-12666-3-git-send-email-bigeasy@linutronix.de Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
| * cpu/hotplug: Rework callback invocation logicThomas Gleixner2016-09-021-82/+80
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | This is preparation for the following patch. This rework here changes the arguments of cpuhp_invoke_callback(). It passes now `state' and whether `startup' or `teardown' callback should be invoked. The callback then is looked up by the function. The following is a clanup of callers: - cpuhp_issue_call() has one argument less - struct cpuhp_cpu_state (which is used by the hotplug thread) gets also its callback removed. The decision if it is a single callback invocation moved to the `single' variable. Also a `bringup' variable has been added to distinguish between startup and teardown callback. - take_cpu_down() needs to start one step earlier. We always get here via CPUHP_TEARDOWN_CPU callback. Before that change cpuhp_ap_states + CPUHP_TEARDOWN_CPU pointed to an empty entry because TEARDOWN is saved in bp_states for this reason. Now that we use cpuhp_get_step() to lookup the state we must explicitly skip it in order not to invoke it twice. Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de> Cc: Mark Rutland <mark.rutland@arm.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Will Deacon <will.deacon@arm.com> Cc: rt@linutronix.de Link: http://lkml.kernel.org/r/1471024183-12666-2-git-send-email-bigeasy@linutronix.de Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
| * cpu/hotplug: Prevent alloc/free of irq descriptors during CPU up/down (again)Boris Ostrovsky2016-08-101-0/+8
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Now that Xen no longer allocates irqs in _cpu_up() we can restore commit: a89941816726 ("hotplug: Prevent alloc/free of irq descriptors during cpu up/down") Signed-off-by: Boris Ostrovsky <boris.ostrovsky@oracle.com> Reviewed-by: Juergen Gross <jgross@suse.com> Acked-by: Thomas Gleixner <tglx@linutronix.de> Cc: Anna-Maria Gleixner <anna-maria@linutronix.de> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de> Cc: david.vrabel@citrix.com Cc: xen-devel@lists.xenproject.org Link: http://lkml.kernel.org/r/1470244948-17674-3-git-send-email-boris.ostrovsky@oracle.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
* | Merge branch 'core-rcu-for-linus' of ↵Linus Torvalds2016-10-031-0/+1
|\ \ | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip Pull RCU updates from Ingo Molnar: "The main changes in this cycle were: - Expedited grace-period changes, most notably avoiding having user threads drive expedited grace periods, using a workqueue instead. - Miscellaneous fixes, including a performance fix for lists that was sent with the lists modifications. - CPU hotplug updates, most notably providing exact CPU-online tracking for RCU. This will in turn allow removal of the checks supporting RCU's prior heuristic that was based on the assumption that CPUs would take no longer than one jiffy to come online. - Torture-test updates. - Documentation updates" * 'core-rcu-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (22 commits) list: Expand list_first_entry_or_null() torture: TOROUT_STRING(): Insert a space between flag and message rcuperf: Consistently insert space between flag and message rcutorture: Print out barrier error as document says torture: Add task state to writer-task stall printk()s torture: Convert torture_shutdown() to hrtimer rcutorture: Convert to hotplug state machine cpu/hotplug: Get rid of CPU_STARTING reference rcu: Provide exact CPU-online tracking for RCU rcu: Avoid redundant quiescent-state chasing rcu: Don't use modular infrastructure in non-modular code sched: Make wake_up_nohz_cpu() handle CPUs going offline rcu: Use rcu_gp_kthread_wake() to wake up grace period kthreads rcu: Use RCU's online-CPU state for expedited IPI retry rcu: Exclude RCU-offline CPUs from expedited grace periods rcu: Make expedited RCU CPU stall warnings respond to controls rcu: Stop disabling expedited RCU CPU stall warnings rcu: Drive expedited grace periods from workqueue rcu: Consolidate expedited grace period machinery documentation: Record reason for rcu_head two-byte alignment ...
| * | cpu/hotplug: Get rid of CPU_STARTING referenceSebastian Andrzej Siewior2016-08-221-1/+1
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | CPU_STARTING is scheduled for removal. There is no use of it in drivers and core code uses it only for compatibility with old-style CPU-hotplug notifiers. This patch removes therefore removes CPU_STARTING from an RCU-related comment. Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
| * | rcu: Provide exact CPU-online tracking for RCUPaul E. McKenney2016-08-221-0/+1
| |/ | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Up to now, RCU has assumed that the CPU-online process makes it from CPU_UP_PREPARE to set_cpu_online() within one jiffy. Given the recent rise of virtualized environments, this assumption is very clearly obsolete. Failing to meet this deadline can result in RCU paying attention to an incoming CPU for one jiffy, then ignoring it until the grace period following the one in which that CPU sets itself online. This situation might prove to be fatally disappointing to any RCU read-side critical sections that had the misfortune to execute during the time in which RCU was ignoring the slow-to-come-online CPU. This commit therefore updates RCU's internal CPU state-tracking information at notify_cpu_starting() time, thus providing RCU with an exact transition of the CPU's state from offline to online. Note that this means that incoming CPUs must not use RCU read-side critical section (other than those of SRCU) until notify_cpu_starting() time. Note also that the CPU_STARTING notifiers -are- allowed to use RCU read-side critical sections. (Of course, CPU-hotplug notifiers are rapidly becoming obsolete, so you need to act fast!) If a given architecture or CPU family needs to use RCU read-side critical sections earlier, the call to rcu_cpu_starting() from notify_cpu_starting() will need to be architecture-specific, with architectures that need early use being required to hand-place the call to rcu_cpu_starting() at some point preceding the call to notify_cpu_starting(). Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
* / cpu/hotplug: Allow suspend/resume CPU to be specifiedJames Morse2016-08-261-4/+5
|/ | | | | | | | | | | | | | | | | | | | | | | | | | | | disable_nonboot_cpus() assumes that the lowest numbered online CPU is the boot CPU, and that this is the correct CPU to run any power management code on. On x86 this is always correct, as CPU0 cannot (easily) by taken offline. On arm64 CPU0 can be taken offline. For hibernate/resume this means we may hibernate on a CPU other than CPU0. If the system is rebooted with kexec 'CPU0' will be assigned to a different physical CPU. This complicates hibernate/resume as now we can't trust the CPU numbers. Arch code can find the correct physical CPU, and ensure it is online before resume from hibernate begins, but also needs to influence disable_nonboot_cpus()s choice of CPU. Rename disable_nonboot_cpus() as freeze_secondary_cpus() and add an argument indicating which CPU should be left standing. Follow the logic in migrate_to_reboot_cpu() to use the lowest numbered online CPU if the requested CPU is not online. Add disable_nonboot_cpus() as an inline function that has the existing behaviour. Cc: Rafael J. Wysocki <rjw@rjwysocki.net> Reviewed-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: James Morse <james.morse@arm.com> Signed-off-by: Will Deacon <will.deacon@arm.com>
* timers/core: Correct callback order during CPU hot plugRichard Cochran2016-07-281-5/+10
| | | | | | | | | | | | | | | | | | | | | | | | | On the tear-down path, the dead CPU callback for the timers was misplaced within the 'cpuhp_state' enumeration. There is a hidden dependency between the timers and block multiqueue. The timers callback must happen before the block multiqueue callback otherwise a RCU stall occurs. Move the timers callback to the proper place in the state machine. Reported-and-tested-by: Jon Hunter <jonathanh@nvidia.com> Reported-by: kbuild test robot <lkp@intel.com> Fixes: 24f73b99716a ("timers/core: Convert to hotplug state machine") Signed-off-by: Richard Cochran <rcochran@linutronix.de> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de> Cc: Rasmus Villemoes <linux@rasmusvillemoes.dk> Cc: John Stultz <john.stultz@linaro.org> Cc: rt@linutronix.de Cc: Oleg Nesterov <oleg@redhat.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Link: http://lkml.kernel.org/r/1469610498-25914-1-git-send-email-rcochran@linutronix.de Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Ingo Molnar <mingo@kernel.org>
* rcu: Convert rcutree to hotplug state machineThomas Gleixner2016-07-151-0/+14
| | | | | | | | | | | | | | | Straight forward conversion to the state machine. Though the question arises whether this needs really all these state transitions to work. Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Anna-Maria Gleixner <anna-maria@linutronix.de> Reviewed-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: rt@linutronix.de Link: http://lkml.kernel.org/r/20160713153337.982013161@linutronix.de Signed-off-by: Ingo Molnar <mingo@kernel.org>
* smp/cfd: Convert core to hotplug state machineRichard Weinberger2016-07-151-0/+9
| | | | | | | | | | | | | | | | | | | | | Install the callbacks via the state machine. They are installed at runtime so smpcfd_prepare_cpu() needs to be invoked by the boot-CPU. Signed-off-by: Richard Weinberger <richard@nod.at> [ Added the dropped CPU dying case back in. ] Signed-off-by: Richard Cochran <rcochran@linutronix.de> Signed-off-by: Anna-Maria Gleixner <anna-maria@linutronix.de> Reviewed-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de> Cc: Davidlohr Bueso <dave@stgolabs> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Mel Gorman <mgorman@techsingularity.net> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Rasmus Villemoes <linux@rasmusvillemoes.dk> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: rt@linutronix.de Link: http://lkml.kernel.org/r/20160713153337.818376366@linutronix.de Signed-off-by: Ingo Molnar <mingo@kernel.org>
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