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Re: [Qemu-devel] TSC frequency configuration & invtsc migration (was Re:
From: |
Paolo Bonzini |
Subject: |
Re: [Qemu-devel] TSC frequency configuration & invtsc migration (was Re: [PATCH 4/4] kvm: Allow migration with invtsc) |
Date: |
Tue, 10 Jan 2017 17:36:48 +0100 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.5.1 |
On 05/01/2017 11:48, Marcelo Tosatti wrote:
>> Host A has TSC scaling, host B doesn't have TSC scaling. We want
>> to be able to start the VM on host A, and migrate to B. In this
>> case, the only possible solution is to use B's frequency when
>> starting the VM. The QEMU process doesn't have enough information
>> to make that decision.
> That is a good point. But again, its a special case and
> should be supported by -cpu xxx,tsc-frequency=zzzz.
I don't think this is a scenario that can work reliably. The computed
TSC frequency may vary by 0.5% or so on every boot (e.g. you may get
2497000 kHz or 2511000 kHz for a 2.5 GHz TSC). You can start the VM on
host A, reboot host B, and then you'll be unable to migrate.
Paolo
- Re: [Qemu-devel] [libvirt] TSC frequency configuration & invtsc migration (was Re: [PATCH 4/4] kvm: Allow migration with invtsc), (continued)
- Re: [Qemu-devel] TSC frequency configuration & invtsc migration (was Re: [PATCH 4/4] kvm: Allow migration with invtsc), Marcelo Tosatti, 2017/01/06
- [Qemu-devel] How to make dest host abort migration safely (was Re: [PATCH 4/4] kvm: Allow migration with invtsc), Eduardo Habkost, 2017/01/08
- Re: [Qemu-devel] How to make dest host abort migration safely (was Re: [PATCH 4/4] kvm: Allow migration with invtsc), Dr. David Alan Gilbert, 2017/01/09
- [Qemu-devel] Exporting kvm_max_guest_tsc_khz to userspace (was Re: [PATCH 4/4] kvm: Allow migration with invtsc), Eduardo Habkost, 2017/01/08
- Re: [Qemu-devel] Exporting kvm_max_guest_tsc_khz to userspace (was Re: [PATCH 4/4] kvm: Allow migration with invtsc), Paolo Bonzini, 2017/01/09
- Re: [Qemu-devel] Exporting kvm_max_guest_tsc_khz to userspace (was Re: [PATCH 4/4] kvm: Allow migration with invtsc), Eduardo Habkost, 2017/01/11
- Re: [Qemu-devel] Exporting kvm_max_guest_tsc_khz to userspace (was Re: [PATCH 4/4] kvm: Allow migration with invtsc), Paolo Bonzini, 2017/01/11
- Re: [Qemu-devel] TSC frequency configuration & invtsc migration (was Re: [PATCH 4/4] kvm: Allow migration with invtsc),
Paolo Bonzini <=
- Re: [Qemu-devel] TSC frequency configuration & invtsc migration (was Re: [PATCH 4/4] kvm: Allow migration with invtsc), Eduardo Habkost, 2017/01/11
- Re: [Qemu-devel] TSC frequency configuration & invtsc migration (was Re: [PATCH 4/4] kvm: Allow migration with invtsc), Marcelo Tosatti, 2017/01/18
- Re: [Qemu-devel] TSC frequency configuration & invtsc migration (was Re: [PATCH 4/4] kvm: Allow migration with invtsc), Eduardo Habkost, 2017/01/18