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Re: [PATCH] target/i386: always create kvmclock device
From: |
Vitaly Kuznetsov |
Subject: |
Re: [PATCH] target/i386: always create kvmclock device |
Date: |
Tue, 22 Sep 2020 17:19:02 +0200 |
"Dr. David Alan Gilbert" <dgilbert@redhat.com> writes:
> * Antoine Damhet (antoine.damhet@blade-group.com) wrote:
>> On Thu, Sep 17, 2020 at 06:44:10PM +0100, Dr. David Alan Gilbert wrote:
>>
>> [...]
>>
>> > > >> >
>> > > >> > Shouldn't the old check used when machine type <= 5.1 in order to
>> > > >> > avoid
>> > > >> > migration incompatibility ?
>> > > >>
>> > > >> Hm, when the check fails we just don't create the device and no error
>> > > >> is
>> > > >> reported, so even if we have kvmclock data in the migration stream but
>> > > >> fail to create it migration will still succeed, right? (not a
>> > > >> migration
>> > > >> expert here :-)
>> > > >
>> > > > When the migration stream is parsed, it'll try and find a "kvmclock"
>> > > > device to pass the data it's reading to; if one doesn't exist it'll
>> > > > fail.
>> > >
>> > > This may happen with an older machine type when the destination is
>> > > running an unfixed QEMU and the source has the fix, right?
>> >
>> > Yes I think so.
>> >
>> > > The solution
>> > > would be to introduce a flag for older machine types (or for new ones)
>> > > like 'kvmclock_always'.
>> >
>> > Yep sounds the normal answer.
>> > (You might want to try it first to trigger the bug)
>>
>> So, I tried the patch and:
>>
>> # patched -> patched
>>
>> Everything working as expected
>>
>> # patched -> unpatched
>>
>> Migration failure with:
>>
>> ```
>> Unknown savevm section or instance 'kvmclock' 0. Make sure that your current
>> VM setup matches your saved VM setup, including any hotplugged devices
>> load of migration failed: Invalid argument
>> ```
>
> Right, that's what I expected and said we need to wire this fix to the
> machine type.
>
v2 with the idea implemented is coming. As I'm not a regular contributor
to machine types, please review thoroughly :-)
--
Vitaly
- Re: [PATCH] target/i386: always create kvmclock device, (continued)
- Re: [PATCH] target/i386: always create kvmclock device, no-reply, 2020/09/17
- Re: [PATCH] target/i386: always create kvmclock device, Antoine Damhet, 2020/09/17
- Re: [PATCH] target/i386: always create kvmclock device, Vitaly Kuznetsov, 2020/09/17
- Re: [PATCH] target/i386: always create kvmclock device, Dr. David Alan Gilbert, 2020/09/17
- Re: [PATCH] target/i386: always create kvmclock device, Vitaly Kuznetsov, 2020/09/17
- Re: [PATCH] target/i386: always create kvmclock device, Dr. David Alan Gilbert, 2020/09/17
- Re: [PATCH] target/i386: always create kvmclock device, Paolo Bonzini, 2020/09/18
- Re: [PATCH] target/i386: always create kvmclock device, Antoine Damhet, 2020/09/18
- Re: [PATCH] target/i386: always create kvmclock device, Dr. David Alan Gilbert, 2020/09/18
- Re: [PATCH] target/i386: always create kvmclock device,
Vitaly Kuznetsov <=
- Re: [PATCH] target/i386: always create kvmclock device, Antoine Damhet, 2020/09/17
Re: [PATCH] target/i386: always create kvmclock device, Paolo Bonzini, 2020/09/18