RE: [Fastboot] [PATCH] i386: move apic init in init_IRQs

["Protasevich, Natalie" <Natalie.Protasevich@UNISYS.com>]

> Vivek Goyal <vgoyal@in.ibm.com> writes:
> > I have attached a patch with the mail which is now using 
> > boot_cpu_physical_apicid to hard set presence of boot cpu 
> instead of 
> > hard_smp_processor_id(). But the interesting questoin 
> remains why BIOS 
> > is not reporting the boot cpu.
> 
> 
> Ok.  I don't know if we care but I do know why we were not 
> seeing the report from the bios about your boot processor.  
> We record information about cpus for up to NR_CPUS, and since 
> you had a UP kernel NR_CPUS was one.
> 
> From your earlier boot log.
> 
> > ACPI: LAPIC (acpi_id[0x00] lapic_id[0x03] enabled) 
> Processor #3 6:10 
> > APIC version 17
> > ACPI: LAPIC (acpi_id[0x01] lapic_id[0x00] enabled) 
> Processor #0 6:10 
> > APIC version 17
> > WARNING: NR_CPUS limit of 1 reached.  Processor ignored.
> > ACPI: LAPIC (acpi_id[0x02] lapic_id[0x01] enabled) 
> Processor #1 6:10 
> > APIC version 17
> > WARNING: NR_CPUS limit of 1 reached.  Processor ignored.
> > ACPI: LAPIC (acpi_id[0x03] lapic_id[0x02] enabled) 
> Processor #2 6:10 
> > APIC version 17
> > WARNING: NR_CPUS limit of 1 reached.  Processor ignored.
> 
> So it looks like we have this problem completely fixed.  
> 
> I don't see a good way to ensure that we always record our 
> boot apicid when we boot a multiple processor system and only 
> use one processor.

Hi Eric,

There is another problem with that patch - it broke ES7000, I kept
getting timer panics. It turned out that check_timer() runs before the
actual APIC destination is set up. The IO-APIC uses
cpu_to_logical_apicid to find the destination - which needs
cpu_2_logical_apicid[] to be filled - which only happens after
processors are booted. At the time when check_timer() runs, it will
always be BAD_APICID (0xFF - broadcast) as the IO-APIC rte destination
for the timer, but ES7000 hardware happened not to support 0xFF so it
panics. I used bios_cpu_apicid[] to bring it up, but
cpu_to_logical_apicid is the only one that is kept up-to-date in the
hotplug case, so I cannot replace it in the cpu_mask_to_apicid(). 

There are probably some ways to fix this such as one below that I tried
(in mpparse.c):

        if (m->mpc_cpuflag & CPU_BOOTPROCESSOR) {
                Dprintk("    Bootup CPU\n");
                boot_cpu_physical_apicid = m->mpc_apicid;
+               cpu_2_logical_apicid[num_processors] = m->mpc_apicid;
        }
it  worked, but looks more like a kludge of course. I think IO-APIC
setup has to happen after processors were brought online and so is
check_timer(), if timer is connected through the IO-APIC.

--Natalie

 
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