Re: port-amd64/58410: x86_patch() panic with core ultra processor

[Martin Husemann <martin%duskware.de@localhost>]

The following reply was made to PR port-amd64/58410; it has been noted by GNATS.

From: Martin Husemann <martin%duskware.de@localhost>
To: matthew green <mrg%eterna23.net@localhost>
Cc: gnats-bugs%netbsd.org@localhost
Subject: Re: port-amd64/58410: x86_patch() panic with core ultra processor
Date: Tue, 6 Aug 2024 08:20:03 +0200

 On Tue, Aug 06, 2024 at 11:49:17AM +1000, matthew green wrote:
 > nicely found.
 > 
 > so, the problem is that the boot cpu is not the first cpu, and
 > we don't handle that right.  good job, us :)
 > 
 > hopefully this isn't too hard to figure out.  i remember we had
 > to do something for it on sparc long long ago, when you could
 > ask the prom to switch cpu, and booting from that cpu would mean
 > the boot cpu was not the first cpu.
 
 We don't really expect the first cpu to be the bootstrap processor,
 and the difference between that and other cpu's is mostly
 
  - start with running main() instead of the trampoline code to wait for
    MP startup
  - allocate the cpu info early (and probably differently) than other CPUs
  - (maybe, MD) make sure the boot CPUs is the last one running when halting
    the machine
 
 It happens on sparc64 a lot, I have several machines that boot on != cpu0
 by default.
 
 But even on x86 we seem to have code to deal (but maybe it has not been
 tested that much). See for example
 
 sys/arch/x86/x86/cpu.c:cpu_attach
 
         /*
          * Boot processor may not be attached first, but the below
          * must be done to allow booting other processors.
          */
         if (!again) {
                 /* Make sure DELAY() (likely i8254_delay()) is initialized. */
                 DELAY(1);
 
                 /*
                  * Basic init.  Compute an approximate frequency for the TSC
                  * using the i8254.  If there's a HPET we'll redo it later.
                  */
                 atomic_or_32(&ci->ci_flags, CPUF_PRESENT | CPUF_PRIMARY);
  
 
 Martin