Messages in this thread Patch in this message | | | Date | Fri, 21 May 2021 09:53:15 +0200 | From | Peter Zijlstra <> | Subject | Re: config SCHED_CORE |
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On Thu, May 20, 2021 at 08:06:07PM -0700, Hugh Dickins wrote: > Hi Peter, > > make oldconfig gave me no help at all on how to decide whether to choose > SCHED_CORE Y or n, beyond it recommending Y. Maybe you'll delete that > option later, or maybe removing the prompt string would silence it.
Ah, you're quite right. I never seem to have gotten around to actually writing anything useful there :/ Similarly the documentation for all this seems to have gone missing too.
Joel, could I ask you to refresh the document to match the current state of things and repost? I still whole hartedly despise this RST crud, it makes it so hard to read / modify the files.
( I think the latest version is here: https://lkml.kernel.org/r/20210324214020.34142-8-joel@joelfernandes.org )
Anyway, how is something like the below, Joel can add a reference to the document once it's there.
--- kernel/Kconfig.preempt | 14 +++++++++++++- 1 file changed, 13 insertions(+), 1 deletion(-)
diff --git a/kernel/Kconfig.preempt b/kernel/Kconfig.preempt index ea1e3331c0ba..3c4566cd20ef 100644 --- a/kernel/Kconfig.preempt +++ b/kernel/Kconfig.preempt @@ -104,4 +104,16 @@ config SCHED_CORE bool "Core Scheduling for SMT" default y depends on SCHED_SMT - + help + This option enables Core scheduling, a means of coordinated task + selection across SMT siblings with the express purpose of creating a + Core wide privilidge boundary. When enabled -- see prctl(PR_SCHED_CORE) + -- task selection will ensure all SMT siblings will execute a task + from the same 'core group', forcing idle when no matching task is found. + + This provides means of mitigation against a number of SMT side-channels; + but is, on its own, insufficient to mitigate all known side-channels. + Notable: the MDS class of attacks require more. + + Default enabled for anything that has SCHED_SMT, when unused there should + be no impact on performance.
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