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Re: [Qemu-ppc] [PATCH] spapr: add "compat" machine option
From: |
Alexander Graf |
Subject: |
Re: [Qemu-ppc] [PATCH] spapr: add "compat" machine option |
Date: |
Tue, 5 Nov 2013 11:27:14 +0100 |
On 05.11.2013, at 10:52, Paolo Bonzini <address@hidden> wrote:
> 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.
The only thing that this really changes is an SPR (MSR in x86 speech) on an
existing cpu model. It's definitely not a new CPU type. If anything it'd be an
option to an existing type.
Alex
- Re: [Qemu-ppc] [PATCH] spapr: add "compat" machine option, Alexey Kardashevskiy, 2013/11/04
- Re: [Qemu-ppc] [PATCH] spapr: add "compat" machine option, Paolo Bonzini, 2013/11/05
- Re: [Qemu-ppc] [PATCH] spapr: add "compat" machine option, Andreas Färber, 2013/11/05
- Re: [Qemu-ppc] [PATCH] spapr: add "compat" machine option, Igor Mammedov, 2013/11/06
- Re: [Qemu-ppc] [PATCH] spapr: add "compat" machine option, Alexey Kardashevskiy, 2013/11/07
- Re: [Qemu-ppc] [PATCH] spapr: add "compat" machine option, Igor Mammedov, 2013/11/07
- Re: [Qemu-ppc] [PATCH] spapr: add "compat" machine option, Alexey Kardashevskiy, 2013/11/08
- Re: [Qemu-ppc] [PATCH] spapr: add "compat" machine option, Andreas Färber, 2013/11/08
- Re: [Qemu-ppc] [PATCH] spapr: add "compat" machine option, Alexey Kardashevskiy, 2013/11/08