sim-se: (Re)add support for retrying system calls.

The previous incarnation of this support used faults to make the CPU
reexecute the system call instruction again and again to prevent
emulating/passing through blocking system calls from blocking gem5 as
a whole. That support was accidentally removed a while ago. This new
version suspends the thread context executing the system call, and
periodically wakes it up to retry using a periodically scheduled event.

Jira Issue: https://gem5.atlassian.net/browse/GEM5-1123

Change-Id: I155fa8205d7ea45e3d102216aeca6ee1979a522f
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/54205
Reviewed-by: Giacomo Travaglini <giacomo.travaglini@arm.com>
Maintainer: Giacomo Travaglini <giacomo.travaglini@arm.com>
Tested-by: kokoro <noreply+kokoro@google.com>
2 files changed