On Sat, Oct 22, 2005 at 09:23:34AM -0600, Eric W. Biederman wrote:
> Vivek Goyal <[email protected]> writes:
[..]
>
>
> >> apic_id_registered expands to:
> >> static inline int apic_id_registered(void)
> >> {
> >> return physid_isset(GET_APIC_ID(apic_read(APIC_ID)), phys_cpu_present_map);
> >> }
> >>
> >> Which indicates to me that the code that, there is something
> >> wrong in the logic of:
> >> if (!check_phys_apicid_present(boot_cpu_physical_apicid)) {
> >> printk("weird, boot CPU (#%d) not listed by the BIOS.\n",
> >> boot_cpu_physical_apicid);
> >> physid_set(hard_smp_processor_id(), phys_cpu_present_map);
> >> }
> >>
> >> Currently we are refering to the boot cpus apicid with 3 different expressions
> >> one of them appears to be wrong.
> >>
> >
> > Looks like apic_id_registered() is failing. I had put two debug printk()
> > statements and to my surprise hard_smp_processor_id() is returning different
> > value then GET_APIC_ID(apic_read(APIC_ID)).
> >
> > source code of hard_smp_processor_id() shows that it is also reading APIC_ID
> > register only. Then how can two values be different. (Until and unless
> > somebody modified the value in between two reads).
>
> It appears the buggy expression is hard_smp_processor_id. Quite
> possibly because it doesn't call apic_read() and instead open codes
> it.
>
> boot_cpu_physical_apicid also returns apicid #1, before we have
> a problem.
>
> So either we want to change hard_smp_processor_id to use apic_read()
> or we can just use boot_cpu_physical_apicid when fixing the apicid present
> bitmap.
>
> > I am pasting another failure log with my debug messages(prefixed with "Debug:").
> > My debug patch is also attached with the mail.
>
> See above but I am pretty certain we know enough to get farther. For
> testing you may want to hard code your first kernel to use the second
> cpu.
>
> The fact that hard_smp_processor_id gets the wrong value makes me wonder
> if your kernel will boot all of the way once we get past this problem.
>
> I suspect if you disassemble the code for hard_smp_processor_id we
> will see the compiler doing the wrong thing.
You are right. hard_smp_processor_id() is hard-coded to zero in case of a
non SMP kernel (include/linux/smp.h) and that's why the problem is happening.
I am booting a non-SMP capture kernel. In case of kexec on panic, we can very
well boot on a cpu whose id is not zero.
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.
Thanks
Vivek
o Removes the unnecessary call to local_irq_disable().
o Kdump was failing while second kernel was coming up. Check for presence
of boot cpu apic id was failing in (apic_id_registered), hence hitting
BUG().
o This should not have failed because before calling setup_local_APIC(), it is
ensured that even if BIOS has not reported boot cpu, then hard set the
prence of it. Problem happens because of usage of hard_smp_processor_id()
which is hardcoded to zero in case of non SMP kernel. In kdump case second
kernel can boot on a cpu whose boot cpu id is not zero.
o Using boot_cpu_physical_apicid instead to hard set the presence of boot cpu.
Signed-off-by: Vivek Goyal <[email protected]>
---
linux-2.6.14-rc4-mm1-16M-root/arch/i386/kernel/apic.c | 3 +--
1 files changed, 1 insertion(+), 2 deletions(-)
diff -puN arch/i386/kernel/apic.c~kdump-i386-apic-verification-failure-fix arch/i386/kernel/apic.c
--- linux-2.6.14-rc4-mm1-16M/arch/i386/kernel/apic.c~kdump-i386-apic-verification-failure-fix 2005-10-24 17:40:08.000000000 +0530
+++ linux-2.6.14-rc4-mm1-16M-root/arch/i386/kernel/apic.c 2005-10-24 18:19:53.000000000 +0530
@@ -1055,7 +1055,6 @@ void __init setup_boot_APIC_clock(void)
using_apic_timer = 1;
local_irq_save(flags);
- local_irq_disable();
calibration_result = calibrate_APIC_clock();
/*
@@ -1299,7 +1298,7 @@ int __init APIC_init(void)
if (!check_phys_apicid_present(boot_cpu_physical_apicid)) {
printk("weird, boot CPU (#%d) not listed by the BIOS.\n",
boot_cpu_physical_apicid);
- physid_set(hard_smp_processor_id(), phys_cpu_present_map);
+ physid_set(boot_cpu_physical_apicid, phys_cpu_present_map);
}
/*
_
-
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