Re: [PATCH v2 0/6] Implement icount=auto using TCG Plugins

[Pierrick Bouvier <pierrick.bouvier@linaro.org>]

A v3 was just sent, with a fix to the algorithm used.

On 5/30/24 10:49, Pierrick Bouvier wrote:
> 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), now
> merged on master.
> 
> 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
> 
> v2
> --
> 
> - Added missing personal Signed-off-by for commits from Alex
> - Fix bad rebase in stubs/meson.build
> - move qtest_{get,set}_virtual_clock to accel/qtest/qtest.c
> - A race condition was identified for plugins init/idle/resume, but is not
>    related to this series, and will be fixed in another one:
>    https://lore.kernel.org/qemu-devel/20240529152219.825680-1-alex.bennee@linaro.org/
> 
> 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 (2):
>    qtest: move qtest_{get,set}_virtual_clock to accel/qtest/qtest.c
>    contrib/plugins: add ips plugin example for cost modeling
> 
>   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                        |   2 -
>   accel/qtest/qtest.c                           |  13 +
>   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                                |  37 +--
>   util/qemu-timer.c                             |  26 ++
>   contrib/plugins/Makefile                      |   1 +
>   plugins/qemu-plugins.symbols                  |   2 +
>   stubs/meson.build                             |   2 +-
>   15 files changed, 389 insertions(+), 39 deletions(-)
>   create mode 100644 contrib/plugins/ips.c
>   rename stubs/{cpus-get-virtual-clock.c => cpus-virtual-clock.c} (68%)
>