Messages in this thread | | | Date | Fri, 25 Jan 2019 16:39:09 +0100 (CET) | From | Thomas Gleixner <> | Subject | Re: [PATCH] x86/speculation: Update TIF_SPEC_IB before ibpb barrier |
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On Wed, 23 Jan 2019, Thomas Gleixner wrote:
> On Fri, 18 Jan 2019, Zhenzhong Duan wrote: > > > When a task is set for updating TIF_SPEC_IB throuth SECCOMP by others > > and it's scheduled in the first time, a stale TIF_SPEC_IB value is > > picked in cond_ibpb(). This is due to TIF_SPEC_IB is updated later at > > __switch_to_xtra(). > > > > Add an extra call to speculation_ctrl_update_tif() to update it before > > IBPB barrier. > > Errm. No. It adds that call to speculation_ctrl_update_tif() for every > mm switch, most of the time for nothing. > > If at all, and we discussed that before and decided not to worry about it > (because it gets fixed up on the next context switch), then you want to > handle ibpb() from there:
Actually we need to do that. It's not only the scheduled in first problem. That whole thing might become completely stale in either direction. Care to whip up a patch?
Thanks,
tglx
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