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Re: [Qemu-devel] [PATCH] spapr: add "compat" machine option
From: |
Paolo Bonzini |
Subject: |
Re: [Qemu-devel] [PATCH] spapr: add "compat" machine option |
Date: |
Tue, 05 Nov 2013 10:52:48 +0100 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:17.0) Gecko/20130923 Thunderbird/17.0.9 |
Il 05/11/2013 10:16, Alexander Graf ha scritto:
>
> On 05.11.2013, at 10:06, Paolo Bonzini <address@hidden> wrote:
>
>> Il 30/09/2013 14:57, Alexey Kardashevskiy ha scritto:
>>>>> Why is the option under -machine instead of -cpu?
>>> Because it is still the same CPU and the guest will still read the real
>>> PVR from the hardware (which it may not support but this is why we need
>>> compatibility mode).
>>
>> How do you support migration from a newer to an older CPU then? I think
>> the guest should never see anything about the hardware CPU model.
>
> POWER can't model that. It always leaks the host CPU information into the
> guest. It's the guest kernel's responsibility to not expose that change to
> user space.
>
> Yes, it's broken :). I'm not even sure there is any sensible way to do live
> migration between different CPU types.
Still in my opinion it should be "-cpu", not "-machine". Even if it's
just a "virtual" CPU model.
Paolo
- Re: [Qemu-devel] [PATCH] spapr: add "compat" machine option, Alexey Kardashevskiy, 2013/11/04
- Re: [Qemu-devel] [PATCH] spapr: add "compat" machine option, Paolo Bonzini, 2013/11/05
- Re: [Qemu-devel] [PATCH] spapr: add "compat" machine option, Andreas Färber, 2013/11/05
- Re: [Qemu-devel] [PATCH] spapr: add "compat" machine option, Igor Mammedov, 2013/11/06
- Re: [Qemu-devel] [PATCH] spapr: add "compat" machine option, Alexey Kardashevskiy, 2013/11/07
- Re: [Qemu-devel] [PATCH] spapr: add "compat" machine option, Igor Mammedov, 2013/11/07
- Re: [Qemu-devel] [PATCH] spapr: add "compat" machine option, Alexey Kardashevskiy, 2013/11/08
- Re: [Qemu-devel] [PATCH] spapr: add "compat" machine option, Andreas Färber, 2013/11/08