From: Paolo Bonzini <pbonzini@redhat.com>
To: Alexander Graf <agraf@suse.de>
Cc: "Nikunj A Dadhania" <nikunj@linux.vnet.ibm.com>,
"Alexey Kardashevskiy" <aik@ozlabs.ru>,
"QEMU Developers" <qemu-devel@nongnu.org>,
"list@suse.de:PReP" <qemu-ppc@nongnu.org>,
"Paul Mackerras" <paulus@samba.org>,
"Andreas Färber" <afaerber@suse.de>
Subject: Re: [Qemu-devel] [PATCH] spapr: add "compat" machine option
Date: Tue, 05 Nov 2013 10:52:48 +0100 [thread overview]
Message-ID: <5278BFF0.8010004@redhat.com> (raw)
In-Reply-To: <2B4B8088-FED7-43C5-A12F-2BDDDAB2A863@suse.de>
Il 05/11/2013 10:16, Alexander Graf ha scritto:
>
> On 05.11.2013, at 10:06, Paolo Bonzini <pbonzini@redhat.com> 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
next prev parent reply other threads:[~2013-11-05 9:53 UTC|newest]
Thread overview: 31+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-09-27 8:06 [Qemu-devel] [PATCH] spapr: add "compat" machine option Alexey Kardashevskiy
2013-09-30 11:25 ` Alexander Graf
2013-09-30 11:52 ` Paolo Bonzini
2013-09-30 12:57 ` Alexey Kardashevskiy
2013-11-05 9:06 ` Paolo Bonzini
2013-11-05 9:16 ` Alexander Graf
2013-11-05 9:52 ` Paolo Bonzini [this message]
2013-11-05 10:27 ` Alexander Graf
2013-11-05 10:33 ` Paolo Bonzini
2013-11-05 10:45 ` Alexey Kardashevskiy
2013-11-05 10:46 ` Paolo Bonzini
2013-11-05 13:53 ` Andreas Färber
2013-11-06 11:36 ` Igor Mammedov
2013-11-07 9:11 ` Alexey Kardashevskiy
2013-11-07 13:36 ` Igor Mammedov
2013-11-08 8:22 ` Alexey Kardashevskiy
2013-11-08 13:20 ` Andreas Färber
2013-11-08 14:57 ` Alexey Kardashevskiy
2013-11-08 15:07 ` Andreas Färber
2013-11-07 14:01 ` Andreas Färber
2013-11-08 8:22 ` [Qemu-devel] [PATCH v2 0/2] " Alexey Kardashevskiy
2013-11-08 8:22 ` [Qemu-devel] [PATCH v2 1/2] cpu: add suboptions support Alexey Kardashevskiy
2013-11-08 8:22 ` [Qemu-devel] [PATCH v2 2/2] target-ppc: add "compat" CPU option Alexey Kardashevskiy
2013-11-08 13:24 ` [Qemu-devel] [PATCH v2 0/2] spapr: add "compat" machine option Andreas Färber
2013-11-06 3:27 ` [Qemu-devel] [PATCH] " Paul Mackerras
2013-09-30 13:22 ` Alexey Kardashevskiy
2013-09-30 14:49 ` Alexander Graf
2013-11-05 2:19 ` Alexey Kardashevskiy
2013-11-05 9:23 ` Alexander Graf
2013-11-06 5:48 ` Paul Mackerras
2013-11-06 12:07 ` Alexander Graf
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