xen on i7-12700

[Greg Troxel <gdt%lexort.com@localhost>]

I have a new-to-me i7-12700, originally built by someone else to run
Arch or Debian.  It has 32 GB of RAM.  It survived extensive
shakedown/load testing with Linux.

I migrated by xen system to it, via install of base netbsd-10 to set
up efi/gpt on internal nvme, then rsync of / and /usr from my old ssd
(in the new system).  I have not yet migrated the zfs partition.  It
boots, zfs works, everything else works.  (X will start but doesn't
look great.  That's ok; this is a server.)

I boot this variously as GENERIC or XEN3_DOM0.  I flip back and forth by
editing /boot.cfg default= entry and reboot.

It has hyperthreading on, and I turned it off.  GENERIC was fine either
way.

My xen install is 4.18 from pkgsrc, up to date from about a month or two
ago, but I don't think it really changed since July.

After testing with GENERIC, I tried to boot xen.  I saw some output, and
then the screen went black and it restarted.  It's fast and hard to
tell, but I think it's crashing in Xen, about 1/3 of the way down the
screen.

The CPU has 8 P cores and 4 E cores.  As I understand it, NetBSD doesn't
understand the difference and just acts like it has 12 CPUs.  And, they
all work, just the E cores are lower power and slower, so scheduling is
theoretically suboptimal but I'm not sure it really matters.

I wondered if Xen was choking on E cores, so I went into the bios and
disabled the E cores.  Xen crashed apparently the same way.

So:

  I am guessing running the debug xen might help; I'll do that next.

  Is there an easy way to tell xen to sleep 1s between each boot step,
  so a video will capture the last output before fail?

  Does anyone have wisdom about P and E cores and Xen?

  Is anyone running xen on a 12th gen intel (or 13/14)?

  Does trying to boom xen dom0 under nvmm make sense?

  Should I just try pvh?  Might as well...

  Any other wisdom?