kernel.git/kernel/cpu.c, branch linux-6.8.y

cpu: Ignore "mitigations" kernel parameter if CPU_MITIGATIONS=n

2024-05-30T07:48:48Z

[ Upstream commit ce0abef6a1d540acef85068e0e82bdf1fbeeb0e9 ] Explicitly disallow enabling mitigations at runtime for kernels that were built with CONFIG_CPU_MITIGATIONS=n, as some architectures may omit code entirely if mitigations are disabled at compile time. E.g. on x86, a large pile of Kconfigs are buried behind CPU_MITIGATIONS, and trying to provide sane behavior for retroactively enabling mitigations is extremely difficult, bordering on impossible. E.g. page table isolation and call depth tracking require build-time support, BHI mitigations will still be off without additional kernel parameters, etc. [ bp: Touchups. ] Signed-off-by: Sean Christopherson Signed-off-by: Borislav Petkov (AMD) Acked-by: Borislav Petkov (AMD) Link: https://lore.kernel.org/r/20240420000556.2645001-3-seanjc@google.com Signed-off-by: Sasha Levin

cpu: Re-enable CPU mitigations by default for !X86 architectures

2024-05-02T14:35:28Z

commit fe42754b94a42d08cf9501790afc25c4f6a5f631 upstream. Rename x86's to CPU_MITIGATIONS, define it in generic code, and force it on for all architectures exception x86. A recent commit to turn mitigations off by default if SPECULATION_MITIGATIONS=n kinda sorta missed that "cpu_mitigations" is completely generic, whereas SPECULATION_MITIGATIONS is x86-specific. Rename x86's SPECULATIVE_MITIGATIONS instead of keeping both and have it select CPU_MITIGATIONS, as having two configs for the same thing is unnecessary and confusing. This will also allow x86 to use the knob to manage mitigations that aren't strictly related to speculative execution. Use another Kconfig to communicate to common code that CPU_MITIGATIONS is already defined instead of having x86's menu depend on the common CPU_MITIGATIONS. This allows keeping a single point of contact for all of x86's mitigations, and it's not clear that other architectures *want* to allow disabling mitigations at compile-time. Fixes: f337a6a21e2f ("x86/cpu: Actually turn off mitigations by default for SPECULATION_MITIGATIONS=n") Closes: https://lkml.kernel.org/r/20240413115324.53303a68%40canb.auug.org.au Reported-by: Stephen Rothwell Reported-by: Michael Ellerman Reported-by: Geert Uytterhoeven Signed-off-by: Sean Christopherson Signed-off-by: Borislav Petkov (AMD) Acked-by: Josh Poimboeuf Acked-by: Borislav Petkov (AMD) Cc: stable@vger.kernel.org Link: https://lore.kernel.org/r/20240420000556.2645001-2-seanjc@google.com Signed-off-by: Greg Kroah-Hartman

x86/cpu: Actually turn off mitigations by default for SPECULATION_MITIGATIONS=n

2024-04-17T09:23:39Z

commit f337a6a21e2fd67eadea471e93d05dd37baaa9be upstream. Initialize cpu_mitigations to CPU_MITIGATIONS_OFF if the kernel is built with CONFIG_SPECULATION_MITIGATIONS=n, as the help text quite clearly states that disabling SPECULATION_MITIGATIONS is supposed to turn off all mitigations by default. │ If you say N, all mitigations will be disabled. You really │ should know what you are doing to say so. As is, the kernel still defaults to CPU_MITIGATIONS_AUTO, which results in some mitigations being enabled in spite of SPECULATION_MITIGATIONS=n. Fixes: f43b9876e857 ("x86/retbleed: Add fine grained Kconfig knobs") Signed-off-by: Sean Christopherson Signed-off-by: Ingo Molnar Reviewed-by: Daniel Sneddon Cc: stable@vger.kernel.org Cc: Linus Torvalds Link: https://lore.kernel.org/r/20240409175108.1512861-2-seanjc@google.com Signed-off-by: Greg Kroah-Hartman

Merge tag 'slab-for-6.8' of git://git.kernel.org/pub/scm/linux/kernel/git/vbabka/slab

2024-01-09T18:36:07Z

Pull slab updates from Vlastimil Babka: - SLUB: delayed freezing of CPU partial slabs (Chengming Zhou) Freezing is an operation involving double_cmpxchg() that makes a slab exclusive for a particular CPU. Chengming noticed that we use it also in situations where we are not yet installing the slab as the CPU slab, because freezing also indicates that the slab is not on the shared list. This results in redundant freeze/unfreeze operation and can be avoided by marking separately the shared list presence by reusing the PG_workingset flag. This approach neatly avoids the issues described in 9b1ea29bc0d7 ("Revert "mm, slub: consider rest of partial list if acquire_slab() fails"") as we can now grab a slab from the shared list in a quick and guaranteed way without the cmpxchg_double() operation that amplifies the lock contention and can fail. As a result, lkp has reported 34.2% improvement of stress-ng.rawudp.ops_per_sec - SLAB removal and SLUB cleanups (Vlastimil Babka) The SLAB allocator has been deprecated since 6.5 and nobody has objected so far. We agreed at LSF/MM to wait until the next LTS, which is 6.6, so we should be good to go now. This doesn't yet erase all traces of SLAB outside of mm/ so some dead code, comments or documentation remain, and will be cleaned up gradually (some series are already in the works). Removing the choice of allocators has already allowed to simplify and optimize the code wiring up the kmalloc APIs to the SLUB implementation. * tag 'slab-for-6.8' of git://git.kernel.org/pub/scm/linux/kernel/git/vbabka/slab: (34 commits) mm/slub: free KFENCE objects in slab_free_hook() mm/slub: handle bulk and single object freeing separately mm/slub: introduce __kmem_cache_free_bulk() without free hooks mm/slub: fix bulk alloc and free stats mm/slub: optimize free fast path code layout mm/slub: optimize alloc fastpath code layout mm/slub: remove slab_alloc() and __kmem_cache_alloc_lru() wrappers mm/slab: move kmalloc() functions from slab_common.c to slub.c mm/slab: move kmalloc_slab() to mm/slab.h mm/slab: move kfree() from slab_common.c to slub.c mm/slab: move struct kmem_cache_node from slab.h to slub.c mm/slab: move memcg related functions from slab.h to slub.c mm/slab: move pre/post-alloc hooks from slab.h to slub.c mm/slab: consolidate includes in the internal mm/slab.h mm/slab: move the rest of slub_def.h to mm/slab.h mm/slab: move struct kmem_cache_cpu declaration to slub.c mm/slab: remove mm/slab.c and slab_def.h mm/mempool/dmapool: remove CONFIG_DEBUG_SLAB ifdefs mm/slab: remove CONFIG_SLAB code from slab common code cpu/hotplug: remove CPUHP_SLAB_PREPARE hooks ...

cpu/hotplug: remove CPUHP_SLAB_PREPARE hooks

2023-12-05T10:17:58Z

The CPUHP_SLAB_PREPARE hooks are only used by SLAB which is removed. SLUB defines them as NULL, so we can remove those altogether. Acked-by: Thomas Gleixner Acked-by: David Rientjes Tested-by: David Rientjes Reviewed-by: Hyeonggon Yoo <42.hyeyoo@gmail.com> Tested-by: Hyeonggon Yoo <42.hyeyoo@gmail.com> Signed-off-by: Vlastimil Babka

Merge tag 'timers_urgent_for_v6.7_rc2' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

2023-11-19T21:35:07Z

Pull timer fix from Borislav Petkov: - Do the push of pending hrtimers away from a CPU which is being offlined earlier in the offlining process in order to prevent a deadlock * tag 'timers_urgent_for_v6.7_rc2' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: hrtimers: Push pending hrtimers away from outgoing CPU earlier

hrtimers: Push pending hrtimers away from outgoing CPU earlier

2023-11-11T17:06:42Z

2b8272ff4a70 ("cpu/hotplug: Prevent self deadlock on CPU hot-unplug") solved the straight forward CPU hotplug deadlock vs. the scheduler bandwidth timer. Yu discovered a more involved variant where a task which has a bandwidth timer started on the outgoing CPU holds a lock and then gets throttled. If the lock required by one of the CPU hotplug callbacks the hotplug operation deadlocks because the unthrottling timer event is not handled on the dying CPU and can only be recovered once the control CPU reaches the hotplug state which pulls the pending hrtimers from the dead CPU. Solve this by pushing the hrtimers away from the dying CPU in the dying callbacks. Nothing can queue a hrtimer on the dying CPU at that point because all other CPUs spin in stop_machine() with interrupts disabled and once the operation is finished the CPU is marked offline. Reported-by: Yu Liao Signed-off-by: Thomas Gleixner Tested-by: Liu Tie Link: https://lore.kernel.org/r/87a5rphara.ffs@tglx

Merge tag 'asm-generic-6.7' of git://git.kernel.org/pub/scm/linux/kernel/git/arnd/asm-generic

2023-11-02T01:28:33Z

Pull ia64 removal and asm-generic updates from Arnd Bergmann: - The ia64 architecture gets its well-earned retirement as planned, now that there is one last (mostly) working release that will be maintained as an LTS kernel. - The architecture specific system call tables are updated for the added map_shadow_stack() syscall and to remove references to the long-gone sys_lookup_dcookie() syscall. * tag 'asm-generic-6.7' of git://git.kernel.org/pub/scm/linux/kernel/git/arnd/asm-generic: hexagon: Remove unusable symbols from the ptrace.h uapi asm-generic: Fix spelling of architecture arch: Reserve map_shadow_stack() syscall number for all architectures syscalls: Cleanup references to sys_lookup_dcookie() Documentation: Drop or replace remaining mentions of IA64 lib/raid6: Drop IA64 support Documentation: Drop IA64 from feature descriptions kernel: Drop IA64 support from sig_fault handlers arch: Remove Itanium (IA-64) architecture

Merge tag 'rcu-next-v6.7' of git://git.kernel.org/pub/scm/linux/kernel/git/frederic/linux-dynticks

2023-10-31T04:01:41Z

Pull RCU updates from Frederic Weisbecker: - RCU torture, locktorture and generic torture infrastructure updates that include various fixes, cleanups and consolidations. Among the user visible things, ftrace dumps can now be found into their own file, and module parameters get better documented and reported on dumps. - Generic and misc fixes all over the place. Some highlights: * Hotplug handling has seen some light cleanups and comments * An RCU barrier can now be triggered through sysfs to serialize memory stress testing and avoid OOM * Object information is now dumped in case of invalid callback invocation * Also various SRCU issues, too hard to trigger to deserve urgent pull requests, have been fixed - RCU documentation updates - RCU reference scalability test minor fixes and doc improvements. - RCU tasks minor fixes - Stall detection updates. Introduce RCU CPU Stall notifiers that allows a subsystem to provide informations to help debugging. Also cure some false positive stalls. * tag 'rcu-next-v6.7' of git://git.kernel.org/pub/scm/linux/kernel/git/frederic/linux-dynticks: (56 commits) srcu: Only accelerate on enqueue time locktorture: Check the correct variable for allocation failure srcu: Fix callbacks acceleration mishandling rcu: Comment why callbacks migration can't wait for CPUHP_RCUTREE_PREP rcu: Standardize explicit CPU-hotplug calls rcu: Conditionally build CPU-hotplug teardown callbacks rcu: Remove references to rcu_migrate_callbacks() from diagrams rcu: Assume rcu_report_dead() is always called locally rcu: Assume IRQS disabled from rcu_report_dead() rcu: Use rcu_segcblist_segempty() instead of open coding it rcu: kmemleak: Ignore kmemleak false positives when RCU-freeing objects srcu: Fix srcu_struct node grpmask overflow on 64-bit systems torture: Convert parse-console.sh to mktemp rcutorture: Traverse possible cpu to set maxcpu in rcu_nocb_toggle() rcutorture: Replace schedule_timeout*() 1-jiffy waits with HZ/20 torture: Add kvm.sh --debug-info argument locktorture: Rename readers_bind/writers_bind to bind_readers/bind_writers doc: Catch-up update for locktorture module parameters locktorture: Add call_rcu_chains module parameter locktorture: Add new module parameters to lock_torture_print_module_parms() ...

Merge tag 'x86-core-2023-10-29-v2' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

2023-10-31T03:37:47Z

Pull x86 core updates from Thomas Gleixner: - Limit the hardcoded topology quirk for Hygon CPUs to those which have a model ID less than 4. The newer models have the topology CPUID leaf 0xB correctly implemented and are not affected. - Make SMT control more robust against enumeration failures SMT control was added to allow controlling SMT at boottime or runtime. The primary purpose was to provide a simple mechanism to disable SMT in the light of speculation attack vectors. It turned out that the code is sensible to enumeration failures and worked only by chance for XEN/PV. XEN/PV has no real APIC enumeration which means the primary thread mask is not set up correctly. By chance a XEN/PV boot ends up with smp_num_siblings == 2, which makes the hotplug control stay at its default value "enabled". So the mask is never evaluated. The ongoing rework of the topology evaluation caused XEN/PV to end up with smp_num_siblings == 1, which sets the SMT control to "not supported" and the empty primary thread mask causes the hotplug core to deny the bringup of the APS. Make the decision logic more robust and take 'not supported' and 'not implemented' into account for the decision whether a CPU should be booted or not. - Fake primary thread mask for XEN/PV Pretend that all XEN/PV vCPUs are primary threads, which makes the usage of the primary thread mask valid on XEN/PV. That is consistent with because all of the topology information on XEN/PV is fake or even non-existent. - Encapsulate topology information in cpuinfo_x86 Move the randomly scattered topology data into a separate data structure for readability and as a preparatory step for the topology evaluation overhaul. - Consolidate APIC ID data type to u32 It's fixed width hardware data and not randomly u16, int, unsigned long or whatever developers decided to use. - Cure the abuse of cpuinfo for persisting logical IDs. Per CPU cpuinfo is used to persist the logical package and die IDs. That's really not the right place simply because cpuinfo is subject to be reinitialized when a CPU goes through an offline/online cycle. Use separate per CPU data for the persisting to enable the further topology management rework. It will be removed once the new topology management is in place. - Provide a debug interface for inspecting topology information Useful in general and extremly helpful for validating the topology management rework in terms of correctness or "bug" compatibility. * tag 'x86-core-2023-10-29-v2' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (23 commits) x86/apic, x86/hyperv: Use u32 in hv_snp_boot_ap() too x86/cpu: Provide debug interface x86/cpu/topology: Cure the abuse of cpuinfo for persisting logical ids x86/apic: Use u32 for wakeup_secondary_cpu[_64]() x86/apic: Use u32 for [gs]et_apic_id() x86/apic: Use u32 for phys_pkg_id() x86/apic: Use u32 for cpu_present_to_apicid() x86/apic: Use u32 for check_apicid_used() x86/apic: Use u32 for APIC IDs in global data x86/apic: Use BAD_APICID consistently x86/cpu: Move cpu_l[l2]c_id into topology info x86/cpu: Move logical package and die IDs into topology info x86/cpu: Remove pointless evaluation of x86_coreid_bits x86/cpu: Move cu_id into topology info x86/cpu: Move cpu_core_id into topology info hwmon: (fam15h_power) Use topology_core_id() scsi: lpfc: Use topology_core_id() x86/cpu: Move cpu_die_id into topology info x86/cpu: Move phys_proc_id into topology info x86/cpu: Encapsulate topology information in cpuinfo_x86 ...