Re: [PATCH v2 1/4] x86/boot: print CPU and APIC ID in bring up failure

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

On 22/05/2025 10:10 am, Jan Beulich wrote:
> On 22.05.2025 09:54, Roger Pau Monne wrote:
>> Print the CPU and APIC ID that fails to respond to the init sequence, or
>> that didn't manage to reach the "callin" state.  Expand a bit the printed
>> error messages.  Otherwise the "Not responding." message is not easy to
>> understand by users.
>>
>> Reported-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
>> Signed-off-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>
>> ---
>> Changes since v1:
>>  - Also print APIC ID.
>> ---
>>  xen/arch/x86/smpboot.c | 6 ++++--
>>  1 file changed, 4 insertions(+), 2 deletions(-)
>>
>> diff --git a/xen/arch/x86/smpboot.c b/xen/arch/x86/smpboot.c
>> index 0189d6c332a4..dbc2f2f1d411 100644
>> --- a/xen/arch/x86/smpboot.c
>> +++ b/xen/arch/x86/smpboot.c
>> @@ -618,10 +618,12 @@ static int do_boot_cpu(int apicid, int cpu)
>>              smp_mb();
>>              if ( bootsym(trampoline_cpu_started) == 0xA5 )
>>                  /* trampoline started but...? */
>> -                printk("Stuck ??\n");
>> +                printk("CPU%u/APICID%u: Didn't finish startup sequence\n",
>> +                       cpu, apicid);
>>              else
>>                  /* trampoline code not run */
>> -                printk("Not responding.\n");
>> +                printk("CPU%u/APICID%u: Not responding to startup\n",
>> +                       cpu, apicid);
>>          }
>>      }
>>  
> Elsewhere I think we print AIC IDs in hex; may be better to do so here, too.
> That may then want some text re-arrangement though, e.g.
>
> "CPU%u: APICID %#x not responding to startup\n"
>
> Thoughts?

Definitely hex.  Elsewhere APIC_ID always has an underscore.

I'd suggest:

"APIC_ID %#x (CPU%u) didn't respond to SIPI\n"

The APIC_ID is the critical detail, and the CPU number is fairly incidental.

Also as we're changing things, lets not retain the STARTUP name seeing
as it only exists on pre-Pentium APICs.  SIPI is what we use these days.

~Andrew