On 3/11/25 02:50, Saanjh Sengupta wrote:
Hi,
I have a couple of questions:
1.
When I use the libstoptrigger.so: in that case the QEMU 's emulation
stops after executing the defined number of instructions. Post this,
the whole QEMU terminates. And while using the libips.so I am
assuming that the QEMU doesn't execute no more than the defined
instructions. Please correct me if I am wrong.
That's correct for both plugins, with the additional note that libips
does this per second only.
2.
In my case, I want the QEMU to start emulation for some time and
PAUSE it's emulation for some time; after it is Paused (it's virtual
time is also to be paused) and then let's say for after 'x' time
period it should resume it's virtual time.
The virtual time variable in ips plugin is only related to this plugin,
and based on how many instructions have been executed, which is
different from what you want to achieve.
Stoptrigger might be a better fit for what you want to do, and instead
of exiting, you want to resume emulation after N insn.
The function qemu_clock_advance_virtual_time() can only be used to move
the time forward, and you can not stop the "virtual time" by design.
image
I have added this segment inside the update_system_time function inside
the ipsPlugin.c. but once the instructions reach to the defined limit
the virtual time does not seem to stop.
Do you have any suggestions on that front?
Regards
Saanjh Sengupta
------------------------------------------------------------------------
*From:* Pierrick Bouvier <pierrick.bouv...@linaro.org>
*Sent:* Wednesday, March 5, 2025 5:20:38 AM
*To:* Saanjh Sengupta <saanjhsengu...@outlook.com>; Philippe Mathieu-
Daudé <phi...@linaro.org>; Paolo Bonzini <pbonz...@redhat.com>; Marc-
André Lureau <marcandre.lur...@redhat.com>
*Cc:* amir.gon...@neuroblade.ai <amir.gon...@neuroblade.ai>; qemu-
de...@nongnu.org <qemu-devel@nongnu.org>; Alex Bennée
<alex.ben...@linaro.org>
*Subject:* Re: Building QEMU as a Shared Library
Hi Saanjh,
depending what you are trying to achieve exactly, plugins can provide a
solution. It's convenient and you can stay on top of QEMU upstream,
without having to create a downstream fork.
We already have plugins for stopping after a given number of
instructions, or slow down execution of a VM:
# stop after executing 1'000'000 instructions:
$ ./build/qemu-system-x86_64 -plugin
./build/contrib/plugins/libstoptrigger,icount=1000000 -d plugin
# execute no more than 1'000'000 instructions per second:
$ ./build/qemu-system-x86_64 -plugin
./build/contrib/plugins/libips.so,ips=1000000 -d plugin
You can see source code associated (./contrib/plugins/stoptrigger.c and
./contrib/plugins/ips.c), to implement something similar to what you
want, but based on time.
Would that satisfy your need?
Regards,
Pierrick
On 3/3/25 21:53, Saanjh Sengupta wrote:
Hi,
Thank you so much for your inputs. I was able to create the .so file of
QEMU.
Actually, what we are trying is to understand and explore possibilities
of Virtual Time Control in QEMU. In short, what I mean to say is an
approach via which I can tell QEMU to emulate for XYZ time when the I
give a trigger and then pause the emulation by itself after the XYZ time
is completed.
On that front itself, do you have any inputs/ideas regarding the same?
Regards
Saanjh Sengupta
------------------------------------------------------------------------
*From:* Pierrick Bouvier <pierrick.bouv...@linaro.org>
*Sent:* Tuesday, February 25, 2025 6:29:44 AM
*To:* Philippe Mathieu-Daudé <phi...@linaro.org>; Paolo Bonzini
<pbonz...@redhat.com>; Marc-André Lureau <marcandre.lur...@redhat.com>
*Cc:* amir.gon...@neuroblade.ai <amir.gon...@neuroblade.ai>; qemu-
de...@nongnu.org <qemu-devel@nongnu.org>; Saanjh Sengupta
<saanjhsengu...@outlook.com>
*Subject:* Re: Building QEMU as a Shared Library
Hi Saanjh,
here is a minimal patch that builds one shared library per target (arch,
mode) where arch is cpu arch, and mode is system or user, and launch
system-aarch64 through a simple driver:
https://github.com/pbo-linaro/qemu/commit/ <https://github.com/pbo-
linaro/qemu/commit/>
fbb39cc64f77d4bf1e5e50795c75b62735bf5c5f <https://github.com/pbo-linaro/
qemu/commit/fbb39cc64f77d4bf1e5e50795c75b62735bf5c5f>
With this, it could be possible to create a driver that can execute any
existing target. It's a sort of single binary for QEMU, but shared
objects are mandatory, and duplicates all the QEMU state. So there is no
real benefit compared to having different processes.
In more, to be able to do concurrent emulations, there are much more
problems to be solved. QEMU state is correctly kept per target, but all
other libraries states are shared. There are various issues if you
launch two emulations at the same time in two threads:
- glib global context
- qemu calls exit in many places, which stops the whole process
- probably other things I didn't explore
At this point, even though qemu targets can be built as shared objects,
I would recommend to use different processes, and implement some form on
IPC to synchronize all this.
Another possibility is to try to build machines without using the
existing main, but I'm not sure it's worth all the hassle.
What are you trying to achieve?
Regards,
Pierrick
On 2/24/25 01:10, Philippe Mathieu-Daudé wrote:
Cc'ing our meson experts
On 22/2/25 14:36, Saanjh Sengupta wrote:
Hi,
I referred to your mailing chains on suggesting QEMU to be built as a
shared library.
*Change meson.build to build QEMU as a shared library (with PIC enabled
for static libraries)*
*
*
Could you please suggest what exactly has to be enabled in the meson.build?
I am confused on that front.
Regards
Saanjh Sengupta
