Re: [Qemu-devel] [PATCH v12 2/6] migration: add postcopy blocktime ctx into MigrationIncomingState

[Juan Quintela <quintela@redhat.com>]

Alexey Perevalov <a.perevalov@samsung.com> wrote:
> This patch adds request to kernel space for UFFD_FEATURE_THREAD_ID,
> in case when this feature is provided by kernel.
>
> PostcopyBlocktimeContext is incapsulated inside postcopy-ram.c,
> due to it's postcopy only feature.
> Also it defines PostcopyBlocktimeContext's instance live time.
> Information from PostcopyBlocktimeContext instance will be provided
> much after postcopy migration end, instance of PostcopyBlocktimeContext
> will live till QEMU exit, but part of it (vcpu_addr,
> page_fault_vcpu_time) used only during calculation, will be released
> when postcopy ended or failed.
>
> To enable postcopy blocktime calculation on destination, need to request
> proper capabiltiy (Patch for documentation will be at the tail of the patch
> set).
>
> As an example following command enable that capability, assume QEMU was
> started with
> -chardev socket,id=charmonitor,path=/var/lib/migrate-vm-monitor.sock
> option to control it
>
> [root@host]#printf "{\"execute\" : \"qmp_capabilities\"}\r\n \
> {\"execute\": \"migrate-set-capabilities\" , \"arguments\":   {
> \"capabilities\": [ { \"capability\": \"postcopy-blocktime\", \"state\":
> true } ] } }" | nc -U /var/lib/migrate-vm-monitor.sock
>
> Or just with HMP
> (qemu) migrate_set_capability postcopy-blocktime on
>
> Reviewed-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
> Signed-off-by: Alexey Perevalov <a.perevalov@samsung.com>

Reviewed-by: Juan Quintela <quintela@redhat.com>