Re: [RFC v2 00/27] Kernel Address Space Isolation

[Alexandre Chartre]

On 7/12/19 2:36 PM, Peter Zijlstra wrote:
> On Fri, Jul 12, 2019 at 02:17:20PM +0200, Alexandre Chartre wrote:
> > On 7/12/19 1:44 PM, Peter Zijlstra wrote:
>
> > > AFAIK3 this wants/needs to be combined with core-scheduling to be
> > > useful, but not a single mention of that is anywhere.
> >
> > No. This is actually an alternative to core-scheduling. Eventually, ASI
> > will kick all sibling hyperthreads when exiting isolation and it needs to
> > run with the full kernel page-table (note that's currently not in these
> > patches).
> >
> > So ASI can be seen as an optimization to disabling hyperthreading: instead
> > of just disabling hyperthreading you run with ASI, and when ASI can't preserve
> > isolation you will basically run with a single thread.
>
> You can't do that without much of the scheduler changes present in the
> core-scheduling patches.

We hope we can do that without the whole core-scheduling mechanism. The idea
is to send an IPI to all sibling hyperthreads. This IPI will interrupt these
sibling hyperthreads and have them wait for a condition that will allow them
to resume execution (for example when re-entering isolation). We are
investigating this in parallel to ASI.

alex.