[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
Re: [Qemu-devel] racing between pause_all_vcpus() and qemu_cpu_stop()
From: |
Alex Bennée |
Subject: |
Re: [Qemu-devel] racing between pause_all_vcpus() and qemu_cpu_stop() |
Date: |
Tue, 02 Oct 2018 11:00:29 +0100 |
User-agent: |
mu4e 1.1.0; emacs 26.1.50 |
Peter Maydell <address@hidden> writes:
> On 1 October 2018 at 19:12, Alex Bennée <address@hidden> wrote:
>> I would have thought the reset code should be scheduled via safe async
>> work to run in the vCPU context. Why should the main loop get involved
>> at all here?
>
> The reset code is much older than the safe-async support for
> running things in the vCPU context... Also, does the safe
> async support work with KVM/HAX/Hypervisor.Framework? The
> reset code has to handle all those, not just TCG.
the *_run_on_cpu functions should be safe for all users although KVM
stuff seems to use the direct run_on_cpu stuff more. The events are
consumed in the wait_io logic that all accelerators share - in the outer
loop in cpus-common.c
> Plus, which vCPU thread would you use?
Each vCPU should reset it's own data. For one thing it avoids issue
with barriers across threads.
> We're resetting
> the entire system, so privileging an arbitrary vCPU
> thread to do that doesn't seem any less odd than using
> the main loop thread.
Sure - but they do give predictable semantics. If in this case the cpu
sourcing the request scheduled async tasks to stop the cpu to everything
else and a safe task to it's own thread it can be assured everyone has
done their "work" (stopping in this case) and is in a known state.
Does qemu_system_reset_request() make any particular promises of what
order things should happen in?
--
Alex Bennée
- [Qemu-devel] racing between pause_all_vcpus() and qemu_cpu_stop(), Peter Maydell, 2018/10/01
- Re: [Qemu-devel] racing between pause_all_vcpus() and qemu_cpu_stop(), Alex Bennée, 2018/10/01
- Re: [Qemu-devel] racing between pause_all_vcpus() and qemu_cpu_stop(), Peter Maydell, 2018/10/02
- Re: [Qemu-devel] racing between pause_all_vcpus() and qemu_cpu_stop(), Paolo Bonzini, 2018/10/02
- Re: [Qemu-devel] racing between pause_all_vcpus() and qemu_cpu_stop(), Peter Maydell, 2018/10/02
- Re: [Qemu-devel] racing between pause_all_vcpus() and qemu_cpu_stop(), Paolo Bonzini, 2018/10/02
- Re: [Qemu-devel] racing between pause_all_vcpus() and qemu_cpu_stop(), Peter Maydell, 2018/10/02
- Re: [Qemu-devel] racing between pause_all_vcpus() and qemu_cpu_stop(), Paolo Bonzini, 2018/10/02
- Re: [Qemu-devel] racing between pause_all_vcpus() and qemu_cpu_stop(), Peter Maydell, 2018/10/02
- Re: [Qemu-devel] racing between pause_all_vcpus() and qemu_cpu_stop(),
Alex Bennée <=
- Re: [Qemu-devel] racing between pause_all_vcpus() and qemu_cpu_stop(), Peter Maydell, 2018/10/02