use invd instead of wbinvd in real mode start code

[Andy Shevchenko]

On Tue, Feb 18, 2020 at 1:06 PM Heiko Schocher <hs at denx.de> wrote:
> Am 18.02.2020 um 11:45 schrieb Andy Shevchenko:
> > On Tue, Feb 18, 2020 at 7:48 AM Heiko Schocher <hs at denx.de> wrote:

...

> > How the feed back line is organized? I mean how host system will know that
> >   a) we done flash correctly?
> >   b) the booted image is bad or good?
>
> For both questions the answer is, that you need to write a testcase
> which answer this question.
>
> For a) you flash the image in some way through U-Boot commands. You
> start this commands from a tbot testcase written in python and parse
> the output and/or return code of the command and than decide ...
>
> Same for b) reboot the board, check if new version is installed
> by parsing the U-Boot bootlog, than start U-Boot commands to find
> out, if current installed version is good or bad.

Thank you for elaboration.
I hoped and still hope that x86 won't be broken so drastically that I
need real bisection.
Above mentioned test cases is somewhat time consuming (yes, I agree
that is ~one time big effort), and for now it seems much bigger effort
than just guess by reading the code. Maybe in the future I'll consider
to do something like this, but I think that U-Boot may gain some
patches and config option to have BAT cases enabled (like predefined
output on the serial when we consider commit is good and some C&C
interface during the test).

-- 
With Best Regards,
Andy Shevchenko