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From: Paolo Bonzini <pbonzini@redhat.com>
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Date: Thu, 12 Apr 2018 16:11:30 +0200
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Subject: Re: [Qemu-devel] [PATCH] migration: discard RAMBlocks of type
 ram_device
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To: Peter Maydell <peter.maydell@linaro.org>, =?UTF-8?Q?C=c3=a9dric_Le_Goate?= =?UTF-8?Q?r?= <clg@kaod.org>
Cc: "Dr. David Alan Gilbert" <dgilbert@redhat.com>, QEMU Developers <qemu-devel@nongnu.org>, Juan Quintela <quintela@redhat.com>, David Gibson <david@gibson.dropbear.id.au>, Alex Williamson <alex.williamson@redhat.com>, Yulei Zhang <yulei.zhang@intel.com>, "Tian, Kevin" <kevin.tian@intel.com>, joonas.lahtinen@linux.intel.com, zhenyuw@linux.intel.com, Kirti Wankhede <kwankhede@nvidia.com>, zhi.a.wang@intel.com, Eric Blake <eblake@redhat.com>

On 12/04/2018 15:51, Peter Maydell wrote:
> Paolo may have an opinion what the API here should be, but
> at the MemoryRegion level we already have a mix of functions
> memory_region_init_foo_nomigrate() and memory_region_init_foo(),
> which at the moment just control whether we call
> vmstate_register_ram() or not. Is it possible to hook into that,
> so that we default to marking RAMBlocks as not-migrated, and
> when vmstate_register_ram() is called we set the flag to
> "migrated"?

Yes, that sounds pretty.

Paolo

> NB: this probably requires careful thought to make sure we
> don't accidentally break migration compat, but it seems like
> the cleaner approach. At the moment we do weird things if you
> migrate a RAM block that hasn't had its ID string set, IIRC,
> so just not migrating those RAM blocks seems like a better
> plan than mishandling them. It would also mean that the
> vmstate_register/unregister_ram() functions did what they
> claim to do based on the function name, I think.