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.
