Messages in this thread | | | Date | Mon, 19 Nov 2018 14:49:36 +0100 (CET) | From | Jiri Kosina <> | Subject | Re: [Patch v5 11/16] x86/speculation: Add Spectre v2 app to app protection modes |
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On Mon, 19 Nov 2018, Thomas Gleixner wrote:
> > On Sat, 17 Nov 2018, Jiri Kosina wrote: > > > Subject: [PATCH] x86/speculation: enforce STIBP for SECCOMP tasks in lite mode > > > > If 'lite' mode of app2app protection from spectre_v2 is selected on > > kernel command-line, we are currently applying STIBP protection to > > non-dumpable tasks, and tasks that have explicitly requested such > > protection via > > > > prctl(PR_SET_SPECULATION_CTRL, PR_SPEC_INDIR_BRANCH, PR_SPEC_ENABLE, 0, 0); > > > > Let's extend this to cover also SECCOMP tasks (analogically to how we > > apply SSBD protection). > > Right. And SSBD does not fiddle with dumpable. > > Willy had concerns about the (ab)use of dumpable so I'm holding off on that > bit for now.
Yeah. IBPB implementation used to check the dumpability of tasks during rescheduling, but that went away later.
I still think that ideally that 'app2app' setting would toggle how IBPB is being used as well, something along the lines:
lite: - STIBP for the ones marked via prctl() and SECCOMP with the TIF_ flag - ibpb_needed() returning true for the same
strict: - STIBP: as currently implemented - ibpb_needed() returning always true
off: - neither STIBP nor IBPB applied ever
That's give us also some % of performance lost via IBPB back.
Makes sense?
Thanks,
-- Jiri Kosina SUSE Labs
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