Sep 12 – 14, 2022
Europe/Dublin timezone

CPU isolation vs jailbreaking IPIs

Sep 13, 2022, 12:20 PM
"Ulster & Munster" (Clayton Hotel on Burlington Road)

"Ulster & Munster"

Clayton Hotel on Burlington Road

CPU Isolation MC CPU Isolation MC


Valentin Schneider (Red Hat)


CPU isolation comes with a handful of cpumasks to help determine which CPUs can
sanely be interrupted, but those are not always checked when sending an IPI, nor
is it always obvious wether a given cross-call could be omitted (or delayed) if
targeting an isolated CPU.

1 (with 2 and 3 as required foundations) shows a way to defer cross-call
work targeting isolated CPUs to the next kernel entry, but still requires a
manual patching of the actual cross-call.

A grep for "on_each_cpu()" and "smp_call()" on a mainline kernel yields about
350 results. This slot will be about discussing ways to detect and classify
those (remote data retrieval, system wide synchronization...), if and how to
patch them and where to draw the line(s) on system administrator configuration
vs what is expected of the kernel.

I agree to abide by the anti-harassment policy Yes

Primary author

Valentin Schneider (Red Hat)

Presentation materials

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