user/sven/linux.git/kernel/cpu.c, branch v4.9.329

random: clear fast pool, crng, and batches in cpuhp bring up

2022-06-25T09:45:10Z

commit 3191dd5a1179ef0fad5a050a1702ae98b6251e8f upstream. For the irq randomness fast pool, rather than having to use expensive atomics, which were visibly the most expensive thing in the entire irq handler, simply take care of the extreme edge case of resetting count to zero in the cpuhp online handler, just after workqueues have been reenabled. This simplifies the code a bit and lets us use vanilla variables rather than atomics, and performance should be improved. As well, very early on when the CPU comes up, while interrupts are still disabled, we clear out the per-cpu crng and its batches, so that it always starts with fresh randomness. Cc: Thomas Gleixner Cc: Peter Zijlstra Cc: Theodore Ts'o Cc: Sultan Alsawaf Cc: Dominik Brodowski Acked-by: Sebastian Andrzej Siewior Signed-off-by: Jason A. Donenfeld Signed-off-by: Greg Kroah-Hartman

kernel/cpu: add arch override for clear_tasks_mm_cpumask() mm handling

2020-12-29T12:44:50Z

[ Upstream commit 8ff00399b153440c1c83e20c43020385b416415b ] powerpc/64s keeps a counter in the mm which counts bits set in mm_cpumask as well as other things. This means it can't use generic code to clear bits out of the mask and doesn't adjust the arch specific counter. Add an arch override that allows powerpc/64s to use clear_tasks_mm_cpumask(). Signed-off-by: Nicholas Piggin Reviewed-by: Aneesh Kumar K.V Acked-by: Peter Zijlstra (Intel) Signed-off-by: Michael Ellerman Link: https://lore.kernel.org/r/20201126102530.691335-4-npiggin@gmail.com Signed-off-by: Sasha Levin

x86/speculation: Remove redundant arch_smt_update() invocation

2020-04-24T05:58:57Z

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 Signed-off-by: Thomas Gleixner Cc: Cc: Cc: Cc: Cc: Cc: Link: https://lkml.kernel.org/r/e2e064f2-e8ef-42ca-bf4f-76b612964752@default Cc: Guenter Roeck Signed-off-by: Greg Kroah-Hartman

cpu/hotplug, stop_machine: Fix stop_machine vs hotplug order

2020-02-28T14:42:16Z

[ 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" Debugged-by: Tejun Heo Signed-off-by: Peter Zijlstra (Intel) Tested-by: "Paul E. McKenney" Signed-off-by: Sasha Levin

cpu/SMT: State SMT is disabled even with nosmt and without "=force"

2019-11-25T08:53:32Z

[ 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 Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Thomas Gleixner Link: http://lkml.kernel.org/r/20181004172227.10094-1-bp@alien8.de Signed-off-by: Ingo Molnar Signed-off-by: Sasha Levin

cpu/speculation: Uninline and export CPU mitigations helpers

2019-11-16T09:29:54Z

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 Signed-off-by: Paolo Bonzini Signed-off-by: Thomas Gleixner Signed-off-by: Ben Hutchings Signed-off-by: Greg Kroah-Hartman

cpu/speculation: Warn on unsupported mitigations= parameter

2019-07-10T07:55:39Z

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 Signed-off-by: Thomas Gleixner Acked-by: Josh Poimboeuf Cc: Peter Zijlstra Cc: Jiri Kosina Cc: Greg Kroah-Hartman Cc: Ben Hutchings Cc: stable@vger.kernel.org Link: https://lkml.kernel.org/r/20190516070935.22546-1-geert@linux-m68k.org Signed-off-by: Greg Kroah-Hartman

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

2019-06-11T10:22:48Z

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+ # 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 Signed-off-by: Greg Kroah-Hartman

cpu/speculation: Add 'mitigations=' cmdline option

2019-05-14T17:19:41Z

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 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 [bwh: Backported to 4.9: adjust filename] Signed-off-by: Ben Hutchings Signed-off-by: Greg Kroah-Hartman

x86/speculation: Rework SMT state change

2019-05-14T17:19:36Z

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 Reviewed-by: Ingo Molnar Cc: Peter Zijlstra Cc: Andy Lutomirski Cc: Linus Torvalds Cc: Jiri Kosina Cc: Tom Lendacky Cc: Josh Poimboeuf Cc: Andrea Arcangeli Cc: David Woodhouse Cc: Tim Chen Cc: Andi Kleen Cc: Dave Hansen Cc: Casey Schaufler Cc: Asit Mallick Cc: Arjan van de Ven Cc: Jon Masters Cc: Waiman Long Cc: Greg KH Cc: Dave Stewart Cc: Kees Cook Link: https://lkml.kernel.org/r/20181125185004.521974984@linutronix.de [bwh: Backported to 4.9: adjust context] Signed-off-by: Ben Hutchings Signed-off-by: Greg Kroah-Hartman