Andrew Fish [mailto:af...@apple.com] wrote:
On Aug 1, 2014, at 2:48 PM, Jordan Justen <jljus...@gmail.com
<mailto:jljus...@gmail.com> > wrote:
On Fri, Aug 1, 2014 at 8:12 AM, Scott Duplichan <sc...@notabs.org
<mailto:sc...@notabs.org> > wrote:
Chen Fan [mailto:chen.fan.f...@cn.fujitsu.com] wrote:
With this patch set, the APs are launched even when
a project never uses mpservice. To minimize boot time
it would be good if no AP launch code runs unless
mpservice is actually used.
I think most need need to start the APs regardless. For example,
nearly all systems should program the MTRRs the same for all APs.
You also have to setup SMM on the APs, and the APs have to be in a "well known
state" when the OS is booted. This state is defined
in the MP Spec 1.4 (might have moved to ACPI, since MP spec last update was
1997).
Thanks,
Andrew Fish
AMD reference code does all the AP init needed for OS use. I don't know if the
same is true for Intel.
I know IBV code bases launch APs for SMM setup as you mention, and also for
gathering info for
use in SMBIOS tables. On the other hand, is there any disadvantage to making AP
launch part
of MpService? This is how IBVs do it, as I recall.
I know of two cases where launching APs outside of MpService is undesirable.
One is the standard
EDK2 Duet. When Duet starts, any AP setup beyond that done by the reference
code has already
been handled by the existing BIOS. The second case is when Duet is used as a
coreboot payload.
Any needed AP launch will have already been done by coreboot.
Thanks,
Scott
If a system has a way to know that there are no APs, then some time
could be saved.
-Jordan
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