Messages in this thread | | | From | Joel Fernandes <> | Date | Fri, 21 May 2021 07:18:54 -0400 | Subject | Re: config SCHED_CORE |
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On Fri, May 21, 2021 at 3:53 AM Peter Zijlstra <peterz@infradead.org> wrote: > > 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.
Sure thing, Peter! I will work on it and post a patch.
- Joel
> > --- > 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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