Help my SMP is broken???

[John Baldwin]

On Tuesday 13 July 2004 05:00 pm, Willem Jan Withagen wrote:
> ----- Original Message -----
> From: "John Baldwin" <jhb at FreeBSD.org>
>
> > On Tuesday 13 July 2004 09:22 am, Willem Jan Withagen wrote:
> > > > I'm trying to boot my dual opteron box with a recent kernel.
> > > > Without ACPI is boots single processor, with ACPI I get the stuff
> > > > downbelow.
> > > > ACPI APIC Table: <VIAK8  AWRDACPI>
> > > > panic: AP #1 (PHY# 1) failed!
> > > > cpuid = 0;
> > > > Stack backtrace:
> > > > backtrace() at backtrace+0x17
> > > > panic() at panic+0x1d2
> > > > start_all_aps() at start_all_aps+0x187
> > > > cpu_mp_start() at cpu_mp_start+0x199
> > > > mp_start() at mp_start+0x54
> > > > mi_startup() at mi_startup+0xb8
> > > > btext() at btext+0x2c
> > > > Debugger("panic")
> > > > Stopped at      Debugger+0x4d:  xchgl   %ebx,0x27d461
> > >
> > > I'm trying to figure this one out.....
> > > So I added a printf into init_secondary. This is namely the place where
> > > a variable (mp_naps) is incremented to make it out of the waiting loop
> > > in start_all_aps.
> > >
> > > BUT we never get to init_secondary, which I expected to be called from
> > > an interrupt routine. ini_secondary is called from an asm-sequence in
> > > mpboot.S which suggest that it is the first thing to be called once we
> > > get into 64bit mode???
> > >
> > > Is there anywhere a description on how booting is done on UP or SMP
> > > (let alone SMP amd64??)
> >
> > Basically, when a CPU is started up, it starts up in 8086-style real mode
> > executing the code in mpboot.s.  That code brings the computer into
> > protected mode and eventually into the same virtual addresses used by the
> > kernel (the mpboot code is dual-mapped to allow for this transition).  At
> > that point the AP can safely call into the kernel and it calls
> > init_secondary().  If the AP faults during the early boot code it will
> > basically die and never get into init_secondary().  Also, if the IPI is
> > somehow lost then it will never get into init_secondary().
>
> Some of this I sort figured from comments in mpboot.s
>
> So any suggestions on how to debug this...
> Or could this be broken hardware:
>     CPU
>     APIC
>     Motherboard
>     ????

Well, it might be that there's a bug in mpboot.s. :)  I'm not familiar with 
the amd64 bootstrap though, peter at FreeBSD.org is the most familiar with it.

> I'll try and boot
>  - the amd64 version of Windows XP, to see what happens.
>  - FreeBSD/amd64 in UP with APCI
> and see what goes??
>
> What exactly is the AP??? and what is an IPI??
> Perhaps stuppid questions, but I'm sort of 10 years out of processors and
> stuff.

AP = Application Processor in Intel lingo.  The boot processor is called the 
BSP and all other CPUs are called APs.
IPI = Inter-Processor Interrupt.  Basically, one CPU sends an interrupt 
message to one or more CPUs.

-- 
John Baldwin <jhb at FreeBSD.org>  <><  http://www.FreeBSD.org/~jhb/
"Power Users Use the Power to Serve"  =  http://www.FreeBSD.org