Let APs wait until the BSP has completed the register updates to remove
the CPU. This makes sure all APs stay in SMM mode until the CPU
hot-unplug operation is complete, which in turn makes sure the ACPI lock
is released only after the CPU hot-unplug operation is complete.
Some background: The CPU hotplug SMI is triggered from an ACPI function
which is protected by an ACPI lock. The ACPI function is in the ACPI
tables generated by qemu.
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
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