pm24.git/kernel/cpu.c, branch v5.2-rc4

x86/power: Fix 'nosmt' vs hibernation triple fault during resume

2019-06-03T10:02:03Z

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that is being resumed, which in turn means that all the HT siblings are all of a sudden mwaiting on address which is no longer valid.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+ # v4.19+ Debugged-by: Thomas Gleixner Fixes: 0cc3cd21657b ("cpu/hotplug: Boot HT siblings at least once") Signed-off-by: Jiri Kosina Acked-by: Pavel Machek Reviewed-by: Thomas Gleixner Reviewed-by: Josh Poimboeuf Signed-off-by: Rafael J. Wysocki

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

2019-05-06T21:50:46Z

Pull timer updates from Ingo Molnar: "This cycle had the following changes: - Timer tracing improvements (Anna-Maria Gleixner) - Continued tasklet reduction work: remove the hrtimer_tasklet (Thomas Gleixner) - Fix CPU hotplug remove race in the tick-broadcast mask handling code (Thomas Gleixner) - Force upper bound for setting CLOCK_REALTIME, to fix ABI inconsistencies with handling values that are close to the maximum supported and the vagueness of when uptime related wraparound might occur. Make the consistent maximum the year 2232 across all relevant ABIs and APIs. (Thomas Gleixner) - various cleanups and smaller fixes" * 'timers-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: tick: Fix typos in comments tick/broadcast: Fix warning about undefined tick_broadcast_oneshot_offline() timekeeping: Force upper bound for setting CLOCK_REALTIME timer/trace: Improve timer tracing timer/trace: Replace deprecated vsprintf pointer extension %pf by %ps timer: Move trace point to get proper index tick/sched: Update tick_sched struct documentation tick: Remove outgoing CPU from broadcast masks timekeeping: Consistently use unsigned int for seqcount snapshot softirq: Remove tasklet_hrtimer xfrm: Replace hrtimer tasklet with softirq hrtimer mac80211_hwsim: Replace hrtimer tasklet with softirq hrtimer

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

2019-05-06T21:44:49Z

Pull CPU hotplug updates from Ingo Molnar: "Two changes in this cycle: - Make the /sys/devices/system/cpu/smt/* files available on all arches, so user space has a consistent way to detect whether SMT is enabled. - Sparse annotation fix" * 'smp-hotplug-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: smpboot: Place the __percpu annotation correctly cpu/hotplug: Create SMT sysfs interface for all arches

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

2019-05-06T21:31:50Z

Pull scheduler updates from Ingo Molnar: "The main changes in this cycle were: - Make nohz housekeeping processing more permissive and less intrusive to isolated CPUs - Decouple CPU-bound workqueue acconting from the scheduler and move it into the workqueue code. - Optimize topology building - Better handle quota and period overflows - Add more RCU annotations - Comment updates, misc cleanups" * 'sched-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (25 commits) nohz_full: Allow the boot CPU to be nohz_full sched/isolation: Require a present CPU in housekeeping mask kernel/cpu: Allow non-zero CPU to be primary for suspend / kexec freeze power/suspend: Add function to disable secondaries for suspend sched/core: Allow the remote scheduler tick to be started on CPU0 sched/nohz: Run NOHZ idle load balancer on HK_FLAG_MISC CPUs sched/debug: Fix spelling mistake "logaritmic" -> "logarithmic" sched/topology: Update init_sched_domains() comment cgroup/cpuset: Update stale generate_sched_domains() comments sched/core: Check quota and period overflow at usec to nsec conversion sched/core: Handle overflow in cpu_shares_write_u64 sched/rt: Check integer overflow at usec to nsec conversion sched/core: Fix typo in comment sched/core: Make some functions static sched/core: Unify p->on_rq updates sched/core: Remove ttwu_activate() sched/core, workqueues: Distangle worker accounting from rq lock sched/fair: Remove unneeded prototype of capacity_of() sched/topology: Skip duplicate group rewrites in build_sched_groups() sched/topology: Fix build_sched_groups() comment ...

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

2019-05-06T20:01:16Z

Pull speculation mitigation update from Ingo Molnar: "This adds the "mitigations=" bootline option, which offers a cross-arch set of options that will work on x86, PowerPC and s390 that will map to the arch specific option internally" * 'core-speculation-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: s390/speculation: Support 'mitigations=' cmdline option powerpc/speculation: Support 'mitigations=' cmdline option x86/speculation: Support 'mitigations=' cmdline option cpu/speculation: Add 'mitigations=' cmdline option

kernel/cpu: Allow non-zero CPU to be primary for suspend / kexec freeze

2019-05-03T17:42:58Z

This patch provides an arch option, ARCH_SUSPEND_NONZERO_CPU, to opt-in to allowing suspend to occur on one of the housekeeping CPUs rather than hardcoded CPU0. This will allow CPU0 to be a nohz_full CPU with a later change. It may be possible for platforms with hardware/firmware restrictions on suspend/wake effectively support this by handing off the final stage to CPU0 when kernel housekeeping is no longer required. Another option is to make housekeeping / nohz_full mask dynamic at runtime, but the complexity could not be justified at this time. Signed-off-by: Nicholas Piggin Signed-off-by: Peter Zijlstra (Intel) Cc: Frederic Weisbecker Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Rafael J . Wysocki Cc: Thomas Gleixner Cc: linuxppc-dev@lists.ozlabs.org Link: https://lkml.kernel.org/r/20190411033448.20842-4-npiggin@gmail.com Signed-off-by: Ingo Molnar

cpu/speculation: Add 'mitigations=' cmdline option

2019-04-17T19:37:28Z

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 Signed-off-by: Thomas Gleixner Tested-by: Jiri Kosina (on x86) Reviewed-by: Jiri Kosina Cc: Borislav Petkov Cc: "H . Peter Anvin" Cc: Andy Lutomirski Cc: Peter Zijlstra Cc: Jiri Kosina Cc: Waiman Long Cc: Andrea Arcangeli Cc: Jon Masters Cc: Benjamin Herrenschmidt Cc: Paul Mackerras Cc: Michael Ellerman Cc: linuxppc-dev@lists.ozlabs.org Cc: Martin Schwidefsky Cc: Heiko Carstens Cc: linux-s390@vger.kernel.org Cc: Catalin Marinas Cc: Will Deacon Cc: linux-arm-kernel@lists.infradead.org Cc: linux-arch@vger.kernel.org Cc: Greg Kroah-Hartman Cc: Tyler Hicks Cc: Linus Torvalds Cc: Randy Dunlap Cc: Steven Price Cc: Phil Auld Link: https://lkml.kernel.org/r/b07a8ef9b7c5055c3a4637c87d07c296d5016fe0.1555085500.git.jpoimboe@redhat.com

cpu/hotplug: Create SMT sysfs interface for all arches

2019-04-02T10:36:56Z

Make the /sys/devices/system/cpu/smt/* files available on all arches, so user space has a consistent way to detect whether SMT is enabled. The 'control' file now shows 'notimplemented' for architectures which don't yet have CONFIG_HOTPLUG_SMT. [ tglx: Make notimplemented a real state ] Signed-off-by: Josh Poimboeuf Signed-off-by: Thomas Gleixner Cc: Andrea Arcangeli Cc: Waiman Long Cc: Peter Zijlstra Cc: Jiri Kosina Link: https://lkml.kernel.org/r/469c2b98055f2c41e75748e06447d592a64080c9.1553635520.git.jpoimboe@redhat.com

cpu/hotplug: Prevent crash when CPU bringup fails on CONFIG_HOTPLUG_CPU=n

2019-03-28T12:34:58Z

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 Signed-off-by: Thomas Gleixner Tested-by: Tianyu Lan Acked-by: Greg Kroah-Hartman Cc: Konrad Wilk Cc: Josh Poimboeuf Cc: Mukesh Ojha Cc: Peter Zijlstra Cc: Jiri Kosina Cc: Rik van Riel Cc: Andy Lutomirski Cc: Micheal Kelley Cc: "K. Y. Srinivasan" Cc: Linus Torvalds Cc: Borislav Petkov Cc: K. Y. Srinivasan Cc: stable@vger.kernel.org Link: https://lkml.kernel.org/r/20190326163811.503390616@linutronix.de

tick: Remove outgoing CPU from broadcast masks

2019-03-23T17:26:43Z

Valentin reported that unplugging a CPU occasionally results in a warning in the tick broadcast code which is triggered when an offline CPU is in the broadcast mask. This happens because the outgoing CPU is not removing itself from the broadcast masks, especially not from the broadcast_force_mask. The removal happens on the control CPU after the outgoing CPU is dead. It's a long standing issue, but the warning is harmless. Rework the hotplug mechanism so that the outgoing CPU removes itself from the broadcast masks after disabling interrupts and removing itself from the online mask. Reported-by: Valentin Schneider Signed-off-by: Thomas Gleixner Tested-by: Valentin Schneider Cc: Frederic Weisbecker Link: https://lkml.kernel.org/r/alpine.DEB.2.21.1903211540180.1784@nanos.tec.linutronix.de