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[RFC,0/5] Implement icount=auto using TCG Plugins

Message ID 20240313105504.341875-1-pierrick.bouvier@linaro.org (mailing list archive)
Headers show
Series Implement icount=auto using TCG Plugins | expand

Message

Pierrick Bouvier March 13, 2024, 10:54 a.m. UTC 
The goal here is to be able to scale temporally execution of qemu-user/system,
using a given number of instructions per second.

We define a virtual clock, that can be late or in advance compared to real time.
When we are in advance, we slow execution (by sleeping) until catching real
time.

Finally, we should be able to cleanup icount=auto mode completely, and keep
icount usage for determistic purposes only.

It is built upon new TCG Plugins inline ops (store + conditional callbacks):
20240312075428.244210-1-pierrick.bouvier@linaro.org

Example in user-mode:

- Retrieve number of instructions to execute /bin/true
$ ./build/qemu-x86_64 -plugin ./build/tests/plugin/libinsn.so -d plugin /bin/true
cpu 0 insns: 120546
total insns: 120546
- Slow execution to match 5 seconds
$ time ./build/qemu-x86_64 -plugin ./build/contrib/plugins/libips,ips=$((120546/5)) /bin/true
real    0m4.985s

Alex Bennée (4):
  sysemu: add set_virtual_time to accel ops
  qtest: use cpu interface in qtest_clock_warp
  sysemu: generalise qtest_warp_clock as qemu_clock_advance_virtual_time
  plugins: add time control API

Pierrick Bouvier (1):
  contrib/plugins: add ips plugin example for cost modelling

 include/qemu/qemu-plugin.h                    |  23 ++
 include/qemu/timer.h                          |  15 ++
 include/sysemu/accel-ops.h                    |  18 +-
 include/sysemu/cpu-timers.h                   |   3 +-
 include/sysemu/qtest.h                        |   1 +
 accel/qtest/qtest.c                           |   1 +
 contrib/plugins/ips.c                         | 239 ++++++++++++++++++
 plugins/api.c                                 |  31 +++
 ...t-virtual-clock.c => cpus-virtual-clock.c} |   5 +
 system/cpus.c                                 |  11 +
 system/qtest.c                                |  27 +-
 util/qemu-timer.c                             |  26 ++
 contrib/plugins/Makefile                      |   1 +
 plugins/qemu-plugins.symbols                  |   2 +
 stubs/meson.build                             |   2 +-
 15 files changed, 379 insertions(+), 26 deletions(-)
 create mode 100644 contrib/plugins/ips.c
 rename stubs/{cpus-get-virtual-clock.c => cpus-virtual-clock.c} (68%)