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Re: [Qemu-devel] [PATCHv4 3/4] cpuid: disable pv eoi for 1.1 and older c
From: |
Juan Quintela |
Subject: |
Re: [Qemu-devel] [PATCHv4 3/4] cpuid: disable pv eoi for 1.1 and older compat types |
Date: |
Wed, 29 Aug 2012 16:43:39 +0200 |
User-agent: |
Gnus/5.13 (Gnus v5.13) Emacs/24.1 (gnu/linux) |
"Michael S. Tsirkin" <address@hidden> wrote:
> On Tue, Aug 28, 2012 at 04:13:38PM -0300, Eduardo Habkost wrote:
>> On Tue, Aug 28, 2012 at 08:43:52PM +0300, Michael S. Tsirkin wrote:
>> > In preparation for adding PV EOI support, disable PV EOI by default for
>> > 1.1 and older machine types, to avoid CPUID changing during migration.
>> >
>> > PV EOI can still be enabled/disabled by specifying it explicitly.
>> > Enable for 1.1
>> > -M pc-1.1 -cpu kvm64,+kvm_pv_eoi
>> > Disable for 1.2
>> > -M pc-1.2 -cpu kvm64,-kvm_pv_eoi
>> >
>>
>> What about users that are already running "qemu-1.1 -M pc-1.1" on a host
>> kernel that supports PV EOI already? They would get PV EOI disabled when
>> migrating to a destination running "qemu-1.2 -M pc-1.1".
>>
>> (On the other hand, people running "qemu-1.1 -M pc-1.1" on a host kernel
>> supporting PV EOI already have migration broken, so there's not much we
>> can do for them)
>
> Exactly.
>
> Talked to Gleb, long term I think we should rework code to make
> it forward-compatible wrt adding new MSRs:
> - source gets list of MSRs to be migrated from KVM and simply sends
> them all
This is a bad idea, each time that we add a new MSR, we broke migration.
A better idea is just to _know_ what MSR's have been used by the guest,
and sent that ones.
> - send all MSRS in key/value format
Instead send all MSR's that have changed by its default value (for some
definition of default value).
> - destination gets list of MSRs to be migrated from KVM and
> only restores the supported ones
it should be the other way around. If source knows that an MSR is not
needed (it has never been read/writen/configured/... depends on the
MSR), then jsut dont' sent it.
> Too late for 1.2?
Yes.
ARM is trying to come with some fix for this (they have the CP15
registers, I think, that look a lot like MSR's. I think that only
solution is what I described here.
Current solution of explicitely list all of them is just a mass (TM).
Later, Juan.)
- Re: [Qemu-devel] [PATCHv4 3/4] cpuid: disable pv eoi for 1.1 and older compat types, (continued)
- Re: [Qemu-devel] [PATCHv4 3/4] cpuid: disable pv eoi for 1.1 and older compat types, Eduardo Habkost, 2012/08/29
- Re: [Qemu-devel] [PATCHv4 3/4] cpuid: disable pv eoi for 1.1 and older compat types, Michael S. Tsirkin, 2012/08/29
- Re: [Qemu-devel] [PATCHv4 3/4] cpuid: disable pv eoi for 1.1 and older compat types, Eduardo Habkost, 2012/08/29
- Re: [Qemu-devel] [PATCHv4 3/4] cpuid: disable pv eoi for 1.1 and older compat types, Michael S. Tsirkin, 2012/08/29
- Re: [Qemu-devel] [PATCHv4 3/4] cpuid: disable pv eoi for 1.1 and older compat types, Eduardo Habkost, 2012/08/29
- Re: [Qemu-devel] [PATCHv4 3/4] cpuid: disable pv eoi for 1.1 and older compat types, Marcelo Tosatti, 2012/08/29
- Re: [Qemu-devel] [PATCHv4 3/4] cpuid: disable pv eoi for 1.1 and older compat types, Marcelo Tosatti, 2012/08/29
- Re: [Qemu-devel] [PATCHv4 3/4] cpuid: disable pv eoi for 1.1 and older compat types, Michael S. Tsirkin, 2012/08/29
- Re: [Qemu-devel] [PATCHv4 3/4] cpuid: disable pv eoi for 1.1 and older compat types, Michael S. Tsirkin, 2012/08/29
- Re: [Qemu-devel] [PATCHv4 3/4] cpuid: disable pv eoi for 1.1 and older compat types, Michael S. Tsirkin, 2012/08/29
- Re: [Qemu-devel] [PATCHv4 3/4] cpuid: disable pv eoi for 1.1 and older compat types,
Juan Quintela <=
Re: [Qemu-devel] [PATCHv4 3/4] cpuid: disable pv eoi for 1.1 and older compat types, Anthony Liguori, 2012/08/29
- Re: [Qemu-devel] [PATCHv4 3/4] cpuid: disable pv eoi for 1.1 and older compat types, Gleb Natapov, 2012/08/29
- Re: [Qemu-devel] [PATCHv4 3/4] cpuid: disable pv eoi for 1.1 and older compat types, Anthony Liguori, 2012/08/29
- Re: [Qemu-devel] [PATCHv4 3/4] cpuid: disable pv eoi for 1.1 and older compat types, Michael S. Tsirkin, 2012/08/29
- Re: [Qemu-devel] [PATCHv4 3/4] cpuid: disable pv eoi for 1.1 and older compat types, Eduardo Habkost, 2012/08/29
- [Qemu-devel] [QEMU 1.2 PATCH] i386: kvm: have a predefined set of default KVM feature bits, Eduardo Habkost, 2012/08/29
- Re: [Qemu-devel] [QEMU 1.2 PATCH] i386: kvm: have a predefined set of default KVM feature bits, Michael S. Tsirkin, 2012/08/29
- Re: [Qemu-devel] [QEMU 1.2 PATCH] i386: kvm: have a predefined set of default KVM feature bits, Marcelo Tosatti, 2012/08/29
Re: [Qemu-devel] [PATCHv4 3/4] cpuid: disable pv eoi for 1.1 and older compat types, Eduardo Habkost, 2012/08/29
[Qemu-devel] [PATCHv4 2/4] pc: refactor compat code, Michael S. Tsirkin, 2012/08/28