Messages in this thread | | | Subject | Re: [RFC PATCH 1/2] x86/ibpb: Skip IBPB when we switch back to same user process | From | Arjan van de Ven <> | Date | Thu, 25 Jan 2018 09:24:53 -0800 |
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> The idea is simple, do what we do for virt. Don't send IPI's to CPUs > that don't need them (in virt's case because the vCPU isn't running, in > our case because we're not in fact running a user process), but mark the > CPU as having needed a TLB flush.
I am really uncomfortable with that idea. You really can't run code safely on a cpu where the TLBs in the CPU are invalid or where a CPU that does (partial) page walks would install invalid PTEs either through actual or through speculative execution.
(in the virt case there's a cheat, since the code is not actually running there isn't a cpu with TLBs live. You can't do that same cheat for this case)
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