kernel.git/arch/x86/kernel/smpboot.c, branch linux-5.12.y

sched/core: Initialize the idle task with preemption disabled

2021-07-14T14:59:16Z

[ Upstream commit f1a0a376ca0c4ef1fc3d24e3e502acbb5b795674 ] As pointed out by commit de9b8f5dcbd9 ("sched: Fix crash trying to dequeue/enqueue the idle thread") init_idle() can and will be invoked more than once on the same idle task. At boot time, it is invoked for the boot CPU thread by sched_init(). Then smp_init() creates the threads for all the secondary CPUs and invokes init_idle() on them. As the hotplug machinery brings the secondaries to life, it will issue calls to idle_thread_get(), which itself invokes init_idle() yet again. In this case it's invoked twice more per secondary: at _cpu_up(), and at bringup_cpu(). Given smp_init() already initializes the idle tasks for all *possible* CPUs, no further initialization should be required. Now, removing init_idle() from idle_thread_get() exposes some interesting expectations with regards to the idle task's preempt_count: the secondary startup always issues a preempt_disable(), requiring some reset of the preempt count to 0 between hot-unplug and hotplug, which is currently served by idle_thread_get() -> idle_init(). Given the idle task is supposed to have preemption disabled once and never see it re-enabled, it seems that what we actually want is to initialize its preempt_count to PREEMPT_DISABLED and leave it there. Do that, and remove init_idle() from idle_thread_get(). Secondary startups were patched via coccinelle: @begone@ @@ -preempt_disable(); ... cpu_startup_entry(CPUHP_AP_ONLINE_IDLE); Signed-off-by: Valentin Schneider Signed-off-by: Ingo Molnar Acked-by: Peter Zijlstra Link: https://lore.kernel.org/r/20210512094636.2958515-1-valentin.schneider@arm.com Signed-off-by: Sasha Levin

x86, sched: Fix the AMD CPPC maximum performance value on certain AMD Ryzen generations

2021-05-19T08:56:34Z

commit 3743d55b289c203d8f77b7cd47c24926b9d186ae upstream. Some AMD Ryzen generations has different calculation method on maximum performance. 255 is not for all ASICs, some specific generations should use 166 as the maximum performance. Otherwise, it will report incorrect frequency value like below: ~ → lscpu | grep MHz CPU MHz: 3400.000 CPU max MHz: 7228.3198 CPU min MHz: 2200.0000 [ mingo: Tidied up whitespace use. ] [ Alexander Monakov : fix 225 -> 255 typo. ] Fixes: 41ea667227ba ("x86, sched: Calculate frequency invariance for AMD systems") Fixes: 3c55e94c0ade ("cpufreq: ACPI: Extend frequency tables to cover boost frequencies") Reported-by: Jason Bagavatsingham Fixed-by: Alexander Monakov Reviewed-by: Rafael J. Wysocki Signed-off-by: Huang Rui Signed-off-by: Ingo Molnar Tested-by: Jason Bagavatsingham Cc: stable@vger.kernel.org Link: https://lore.kernel.org/r/20210425073451.2557394-1-ray.huang@amd.com Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=211791 Signed-off-by: Ingo Molnar Signed-off-by: Greg Kroah-Hartman

x86, sched: Treat Intel SNC topology as default, COD as exception

2021-05-14T08:52:06Z

commit 2c88d45edbb89029c1190bb3b136d2602f057c98 upstream. Commit 1340ccfa9a9a ("x86,sched: Allow topologies where NUMA nodes share an LLC") added a vendor and model specific check to never call topology_sane() for Intel Skylake Server systems where NUMA nodes share an LLC. Intel Ice Lake and Sapphire Rapids CPUs also enumerate an LLC that is shared by multiple NUMA nodes. The LLC on these CPUs is shared for off-package data access but private to the NUMA node for on-package access. Rather than managing a list of allowable SNC topologies, make this SNC topology the default, and treat Intel's Cluster-On-Die (COD) topology as the exception. In SNC mode, Sky Lake, Ice Lake, and Sapphire Rapids servers do not emit this warning: sched: CPU #3's llc-sibling CPU #0 is not on the same node! [node: 1 != 0]. Ignoring dependency. Suggested-by: Peter Zijlstra (Intel) Signed-off-by: Alison Schofield Signed-off-by: Peter Zijlstra (Intel) Acked-by: Dave Hansen Cc: stable@vger.kernel.org Link: https://lkml.kernel.org/r/20210310190233.31752-1-alison.schofield@intel.com Signed-off-by: Greg Kroah-Hartman

ACPI: processor: Fix build when CONFIG_ACPI_PROCESSOR=m

2021-04-07T17:02:43Z

Commit 8cdddd182bd7 ("ACPI: processor: Fix CPU0 wakeup in acpi_idle_play_dead()") tried to fix CPU0 hotplug breakage by copying wakeup_cpu0() + start_cpu0() logic from hlt_play_dead()//mwait_play_dead() into acpi_idle_play_dead(). The problem is that these functions are not exported to modules so when CONFIG_ACPI_PROCESSOR=m build fails. The issue could've been fixed by exporting both wakeup_cpu0()/start_cpu0() (the later from assembly) but it seems putting the whole pattern into a new function and exporting it instead is better. Reported-by: kernel test robot Fixes: 8cdddd182bd7 ("CPI: processor: Fix CPU0 wakeup in acpi_idle_play_dead()") Cc: # 5.10+ Signed-off-by: Vitaly Kuznetsov Signed-off-by: Rafael J. Wysocki

ACPI: processor: Fix CPU0 wakeup in acpi_idle_play_dead()

2021-04-01T11:37:55Z

Commit 496121c02127 ("ACPI: processor: idle: Allow probing on platforms with one ACPI C-state") broke CPU0 hotplug on certain systems, e.g. I'm observing the following on AWS Nitro (e.g r5b.xlarge but other instance types are affected as well): # echo 0 > /sys/devices/system/cpu/cpu0/online # echo 1 > /sys/devices/system/cpu/cpu0/online <10 seconds delay> -bash: echo: write error: Input/output error In fact, the above mentioned commit only revealed the problem and did not introduce it. On x86, to wakeup CPU an NMI is being used and hlt_play_dead()/mwait_play_dead() loops are prepared to handle it: /* * If NMI wants to wake up CPU0, start CPU0. */ if (wakeup_cpu0()) start_cpu0(); cpuidle_play_dead() -> acpi_idle_play_dead() (which is now being called on systems where it wasn't called before the above mentioned commit) serves the same purpose but it doesn't have a path for CPU0. What happens now on wakeup is: - NMI is sent to CPU0 - wakeup_cpu0_nmi() works as expected - we get back to while (1) loop in acpi_idle_play_dead() - safe_halt() puts CPU0 to sleep again. The straightforward/minimal fix is add the special handling for CPU0 on x86 and that's what the patch is doing. Fixes: 496121c02127 ("ACPI: processor: idle: Allow probing on platforms with one ACPI C-state") Signed-off-by: Vitaly Kuznetsov Cc: 5.10+ # 5.10+ Signed-off-by: Rafael J. Wysocki

cpufreq: ACPI: Update arch scale-invariance max perf ratio if CPPC is not there

2021-02-08T12:45:51Z

If the maximum performance level taken for computing the arch_max_freq_ratio value used in the x86 scale-invariance code is higher than the one corresponding to the cpuinfo.max_freq value coming from the acpi_cpufreq driver, the scale-invariant utilization falls below 100% even if the CPU runs at cpuinfo.max_freq or slightly faster, which causes the schedutil governor to select a frequency below cpuinfo.max_freq. That frequency corresponds to a frequency table entry below the maximum performance level necessary to get to the "boost" range of CPU frequencies which prevents "boost" frequencies from being used in some workloads. While this issue is related to scale-invariance, it may be amplified by commit db865272d9c4 ("cpufreq: Avoid configuring old governors as default with intel_pstate") from the 5.10 development cycle which made it extremely easy to default to schedutil even if the preferred driver is acpi_cpufreq as long as intel_pstate is built too, because the mere presence of the latter effectively removes the ondemand governor from the defaults. Distro kernels are likely to include both intel_pstate and acpi_cpufreq on x86, so their users who cannot use intel_pstate or choose to use acpi_cpufreq may easily be affectecd by this issue. If CPPC is available, it can be used to address this issue by extending the frequency tables created by acpi_cpufreq to cover the entire available frequency range (including "boost" frequencies) for each CPU, but if CPPC is not there, acpi_cpufreq has no idea what the maximum "boost" frequency is and the frequency tables created by it cannot be extended in a meaningful way, so in that case make it ask the arch scale-invariance code to to use the "nominal" performance level for CPU utilization scaling in order to avoid the issue at hand. Fixes: db865272d9c4 ("cpufreq: Avoid configuring old governors as default with intel_pstate") Signed-off-by: Rafael J. Wysocki Reviewed-by: Giovanni Gherdovich Acked-by: Peter Zijlstra (Intel)

x86: PM: Register syscore_ops for scale invariance

2021-01-19T16:04:03Z

On x86 scale invariace tends to be disabled during resume from suspend-to-RAM, because the MPERF or APERF MSR values are not as expected then due to updates taking place after the platform firmware has been invoked to complete the suspend transition. That, of course, is not desirable, especially if the schedutil scaling governor is in use, because the lack of scale invariance causes it to be less reliable. To counter that effect, modify init_freq_invariance() to register a syscore_ops object for scale invariance with the ->resume callback pointing to init_counter_refs() which will run on the CPU starting the resume transition (the other CPUs will be taken care of the "online" operations taking place later). Fixes: e2b0d619b400 ("x86, sched: check for counters overflow in frequency invariant accounting") Signed-off-by: Rafael J. Wysocki Signed-off-by: Peter Zijlstra (Intel) Acked-by: Giovanni Gherdovich Link: https://lkml.kernel.org/r/1803209.Mvru99baaF@kreacher

Merge tag 'x86-apic-2020-12-14' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

2020-12-15T02:59:53Z

Pull x86 apic updates from Thomas Gleixner: "Yet another large set of x86 interrupt management updates: - Simplification and distangling of the MSI related functionality - Let IO/APIC construct the RTE entries from an MSI message instead of having IO/APIC specific code in the interrupt remapping drivers - Make the retrieval of the parent interrupt domain (vector or remap unit) less hardcoded and use the relevant irqdomain callbacks for selection. - Allow the handling of more than 255 CPUs without a virtualized IOMMU when the hypervisor supports it. This has made been possible by the above modifications and also simplifies the existing workaround in the HyperV specific virtual IOMMU. - Cleanup of the historical timer_works() irq flags related inconsistencies" * tag 'x86-apic-2020-12-14' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (42 commits) x86/ioapic: Cleanup the timer_works() irqflags mess iommu/hyper-v: Remove I/O-APIC ID check from hyperv_irq_remapping_select() iommu/amd: Fix IOMMU interrupt generation in X2APIC mode iommu/amd: Don't register interrupt remapping irqdomain when IR is disabled iommu/amd: Fix union of bitfields in intcapxt support x86/ioapic: Correct the PCI/ISA trigger type selection x86/ioapic: Use I/O-APIC ID for finding irqdomain, not index x86/hyperv: Enable 15-bit APIC ID if the hypervisor supports it x86/kvm: Enable 15-bit extension when KVM_FEATURE_MSI_EXT_DEST_ID detected iommu/hyper-v: Disable IRQ pseudo-remapping if 15 bit APIC IDs are available x86/apic: Support 15 bits of APIC ID in MSI where available x86/ioapic: Handle Extended Destination ID field in RTE iommu/vt-d: Simplify intel_irq_remapping_select() x86: Kill all traces of irq_remapping_get_irq_domain() x86/ioapic: Use irq_find_matching_fwspec() to find remapping irqdomain x86/hpet: Use irq_find_matching_fwspec() to find remapping irqdomain iommu/hyper-v: Implement select() method on remapping irqdomain iommu/vt-d: Implement select() method on remapping irqdomain iommu/amd: Implement select() method on remapping irqdomain x86/apic: Add select() method on vector irqdomain ...

Merge tag 'sched-core-2020-12-14' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

2020-12-15T02:29:11Z

Pull scheduler updates from Thomas Gleixner: - migrate_disable/enable() support which originates from the RT tree and is now a prerequisite for the new preemptible kmap_local() API which aims to replace kmap_atomic(). - A fair amount of topology and NUMA related improvements - Improvements for the frequency invariant calculations - Enhanced robustness for the global CPU priority tracking and decision making - The usual small fixes and enhancements all over the place * tag 'sched-core-2020-12-14' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (61 commits) sched/fair: Trivial correction of the newidle_balance() comment sched/fair: Clear SMT siblings after determining the core is not idle sched: Fix kernel-doc markup x86: Print ratio freq_max/freq_base used in frequency invariance calculations x86, sched: Use midpoint of max_boost and max_P for frequency invariance on AMD EPYC x86, sched: Calculate frequency invariance for AMD systems irq_work: Optimize irq_work_single() smp: Cleanup smp_call_function*() irq_work: Cleanup sched: Limit the amount of NUMA imbalance that can exist at fork time sched/numa: Allow a floating imbalance between NUMA nodes sched: Avoid unnecessary calculation of load imbalance at clone time sched/numa: Rename nr_running and break out the magic number sched: Make migrate_disable/enable() independent of RT sched/topology: Condition EAS enablement on FIE support arm64: Rebuild sched domains on invariance status changes sched/topology,schedutil: Wrap sched domains rebuild sched/uclamp: Allow to reset a task uclamp constraint value sched/core: Fix typos in comments Documentation: scheduler: fix information on arch SD flags, sched_domain and sched_debug ...

x86: Print ratio freq_max/freq_base used in frequency invariance calculations

2020-12-11T09:30:23Z

The value freq_max/freq_base is a fundamental component of frequency invariance calculations. It may come from a variety of sources such as MSRs or ACPI data, tracking it down when troubleshooting a system could be non-trivial. It is worth saving it in the kernel logs. # dmesg | grep 'Estimated ratio of average max' [ 14.024036] smpboot: Estimated ratio of average max frequency by base frequency (times 1024): 1289 Signed-off-by: Giovanni Gherdovich Signed-off-by: Peter Zijlstra (Intel) Signed-off-by: Ingo Molnar Link: https://lkml.kernel.org/r/20201112182614.10700-4-ggherdovich@suse.cz