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Re: [Qemu-devel] racing between pause_all_vcpus() and qemu_cpu_stop()
From: |
Paolo Bonzini |
Subject: |
Re: [Qemu-devel] racing between pause_all_vcpus() and qemu_cpu_stop() |
Date: |
Tue, 2 Oct 2018 11:59:01 +0200 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.0 |
On 02/10/2018 11:04, Peter Maydell wrote:
> On 2 October 2018 at 09:58, Paolo Bonzini <address@hidden> wrote:
>>
>> First, the reset code should indeed use run_on_cpu (it need not be safe
>> i.e. stop-the-world; just run it in the vCPU thread). It certainly
>> doesn't do this right now.
>
> I don't understand this part. We're resetting the entire world:
> surely we need to stop the entire world first ?
Most of the world is stopped because it only runs with BQL taken. vCPU
isn't, so we ensure it is stopped by: 1) using run_on_cpu to synchronize
with the executed TBs (or KVM_RUN) 2) ensuring the execution loop is
paused after reset, which is the cpu_can_run part that you snipped.
"Safe" CPU work items on the other hand ensure that _no_ vCPU is in the
execution loop, which is overkill here.
Paolo
> (Also, other things use pause_all_vcpus() and hit this race
> condition, like VM suspend and shutdown.)
>
> thanks
> -- PMM
>
- [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 <=
- 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, 2018/10/02
- Re: [Qemu-devel] racing between pause_all_vcpus() and qemu_cpu_stop(), Peter Maydell, 2018/10/02