Re: [Qemu-devel] [PATCH v7] spapr: Add support for time base offset migration

[Alexander Graf <agraf@suse.de>]

On 05/06/2014 04:50 PM, Alexey Kardashevskiy wrote:
> On 05/01/2014 08:37 PM, Alexey Kardashevskiy wrote:
>> This allows guests to have a different timebase origin from the host.
>>
>> This is needed for migration, where a guest can migrate from one host
>> to another and the two hosts might have a different timebase origin.
>> However, the timebase seen by the guest must not go backwards, and
>> should go forwards only by a small amount corresponding to the time
>> taken for the migration.
>>
>> This is only supported for recent POWER hardware which has the TBU40
>> (timebase upper 40 bits) register. That includes POWER6, 7, 8 but not
>> 970.
>>
>> This adds kvm_access_one_reg() to access a special register which is not
>> in env->spr. This requires kvm_set_one_reg/kvm_get_one_reg patch.
>>
>> The feature must be present in the host kernel.
>>
>> This bumps vmstate_spapr::version_id and enables new vmstate_ppc_timebase
>> only for it. Since the vmstate_spapr::minimum_version_id remains
>> unchanged, migration from older QEMU is supported but without
>> vmstate_ppc_timebase.
>>
>> Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru>
>> ---
>> Changes:
>> v7:
>> * migration_duration_ns forced to be between [0...1s]
>> * s/tb/tb_remote/
>> * time_of_the_day_ns is int64_t now as this is what get_clock_realtime()
>> returns
> Still bad? :)

The dependency isn't fulfilled yet :)


Alex