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

From: Alexey Kardashevskiy
Subject: Re: [Qemu-devel] [PATCH v7] spapr: Add support for time base offset migration
Date: Fri, 16 May 2014 01:52:25 +1000
User-agent: Mozilla/5.0 (X11; Linux i686 on x86_64; rv:24.0) Gecko/20100101 Thunderbird/24.5.0

On 05/08/2014 10:27 PM, Alexander Graf wrote:
> 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 <address@hidden>
>>> ---
>>> 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 :)

Thanks to Cornelia, it is now!


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