Re: [coreboot] Patch set updated for coreboot: e0964bb Use broadcast SIPI to startup siblings

[Kyösti Mälkki]

On Mon, 2012-07-02 at 08:43 -0700, ron minnich wrote:
> Hi Sven, this is great, I approved it.
>
> I am going to be looking at something I wanted to mention here. On
> machines with SMP, I want to make hardware main send the SIPI right
> after console is set up, rather than waiting as long as we do now. The
> reason is I need them to get through their startup and be ready to do
> a function in parallel DURING device enumeration. The function in this
> case is loading payload while we enumerate the devices. These are
> quite independent functions and there is no reason to serialise them.
> This is a big change from current practice but we need it for startup
> performance. We have those cores and it is good to use them for
> something other than starting themselves up.
>
> I think the structure of your code lends itself to this use, hence my
> enthusiasm for it.
>
> So, if this causes you to have thoughts, I'd like to hear them :)
>
> ron

Hyper-Threading CPUs will continue to require broadcast SIPI before
romstage. Existing code in cache_as_ram_ht.inc already kicks AP CPUs but
halts them as soon as cache disable bit is unset on all threads.

Could ROMCC be trusted to do SIPI broadcast and SMP init before
romstage? That would move microcode update before cache-as-ram, which
may become a more common requirement too.

BTW: It is not just highend Xeons, many Atoms come in HT-enabled
versions too.

Kyösti