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Re: [Qemu-ppc] [PATCH] RFC: powerpc: add PVR compatibility check
From: |
Alexander Graf |
Subject: |
Re: [Qemu-ppc] [PATCH] RFC: powerpc: add PVR compatibility check |
Date: |
Tue, 5 Nov 2013 17:18:34 +0100 |
On 05.11.2013, at 17:16, Andreas Färber <address@hidden> wrote:
> Am 05.11.2013 07:05, schrieb Alexander Graf:
>>
>>
>> Am 05.11.2013 um 05:00 schrieb Paul Mackerras <address@hidden>:
>>
>>> On Mon, Nov 04, 2013 at 10:05:58AM +0100, Alexander Graf wrote:
>>>>
>>>> Yeah, we really need to check that guest vpcu == host vcpu for HV KVM.
>>>
>>> In general I agree, but the one difficulty I see is that a check for
>>> exact equality will interact badly with qemu's habit of picking a
>>> specific processor version when the user specifies something general
>>> like "POWER7". So if the user does -cpu POWER7 on a machine with
>>> (for example) a POWER7 v2.1 processor, but qemu arbitrarily picks the
>>> PVR for POWER7 v2.3, then it will fail, which will be completely
>>> puzzling to the user -- "I asked for POWER7, and it is a POWER7,
>>> what's the problem??".
>>>
>>> Maybe if the user asks for a non-specific processor type, and the
>>> host's PVR matches the request, then qemu should take the host's PVR
>>> rather than just picking some arbitrary processor version.
>>
>> Yup.
>
> But then it's no longer generally reproducible: "POWER7" won't be
> "POWER7" on another machine.
>
> One thing I original did iirc was to hide the aliases from QMP. You can
> always do stupid things on the command line and then we can blame you,
> but if libvirt and upper layers don't offer "POWER7" to the end user
> then we don't need to worry about the average user misinterpreting its
> semantics.
We could also just be nice and error out with a sane error message:
Your selected CPU POWER7_v10 is not compatible with the host's CPU POWER7_20
with your currently selected KVM mode. Please use the latter or -cpu host.
Alex
- [Qemu-ppc] [PATCH] RFC: powerpc: add PVR compatibility check, Alexey Kardashevskiy, 2013/11/03
- Re: [Qemu-ppc] [PATCH] RFC: powerpc: add PVR compatibility check, Alexander Graf, 2013/11/04
- Re: [Qemu-ppc] [PATCH] RFC: powerpc: add PVR compatibility check, Alexey Kardashevskiy, 2013/11/04
- Re: [Qemu-ppc] [PATCH] RFC: powerpc: add PVR compatibility check, Paul Mackerras, 2013/11/04
- Re: [Qemu-ppc] [PATCH] RFC: powerpc: add PVR compatibility check, Alexander Graf, 2013/11/05
- Re: [Qemu-ppc] [PATCH] RFC: powerpc: add PVR compatibility check, Andreas Färber, 2013/11/05
- Re: [Qemu-ppc] [PATCH] RFC: powerpc: add PVR compatibility check,
Alexander Graf <=
- Re: [Qemu-ppc] [PATCH] RFC: powerpc: add PVR compatibility check, Paul Mackerras, 2013/11/05
- Re: [Qemu-ppc] [PATCH] RFC: powerpc: add PVR compatibility check, Alexander Graf, 2013/11/06