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

From: Alexandre Chartre
Date: Fri Jul 12 2019 - 08:54:04 EST



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.