On 15/06/16 11:26, Jan Beulich wrote:
> Using the bare return value from read_platform_stime() is not suitable
> when local_time_calibration() is going to use its fast path: Divergence
> of several dozen microseconds between NOW() return values on different
> CPUs results when platform and local time don't stay in close sync.
>
> Latch local and platform time on the CPU initiating AP bringup, such
> that the AP can use these values to seed its stime_local_stamp with as
> little of an error as possible. The boot CPU, otoh, can simply
> calculate the correct initial value (other CPUs could do so too with
> even greater accuracy than the approach being introduced, but that can
> work only if all CPUs' TSCs start ticking at the same time, which
> generally can't be assumed to be the case on multi-socket systems).
>
> This slightly defers init_percpu_time() (moved ahead by commit
> dd2658f966 ["x86/time: initialise time earlier during
> start_secondary()"]) in order to reduce as much as possible the gap
> between populating the stamps and consuming them.
>
> Signed-off-by: Jan Beulich <jbeulich@suse.com>

Subject to the style issue spotted by Joao, Reviewed-by: Andrew Cooper
<andrew.cooper3@citrix.com>