Re: [PATCH 8/10] kdump: x86_64 save cpu registers upon crash

[ebiederm@xmission.com (Eric W. Biederman)]

> diff -puN arch/x86_64/kernel/crash.c~x86_64-save-cpu-registers-upon-crash
> arch/x86_64/kernel/crash.c
> ---
> linux-2.6.15-rc1-1M-dynamic/arch/x86_64/kernel/crash.c~x86_64-save-cpu-registers-upon-crash

>  #ifdef CONFIG_SMP
>  static atomic_t waiting_for_crash_ipi;
>  
> @@ -38,6 +106,7 @@ static int crash_nmi_callback(struct pt_
>  		return 1;
>  	local_irq_disable();
>  
> +	crash_save_this_cpu(regs, cpu);
>  	disable_local_APIC();
>  	atomic_dec(&waiting_for_crash_ipi);
>  	/* Assume hlt works */
> @@ -113,4 +182,5 @@ void machine_crash_shutdown(struct pt_re
>  	disable_IO_APIC();
>  #endif
>  
> +	crash_save_self(regs);
>  }

Where did this disable_local_APIC and disable_IO_APIC on x86_64 come
from?  I know we had it on x86 but that was supposed to be a stop gap
until we have the real fix.  Now I know it needs a little more
debugging but the real fix has been written.  Putting it there on
x86_64 makes the code less reliable and it allows things to start
depending on it. 

Please don't saving of the apics to x86_64 propagate this to x86_64.

The rest of the patch looks fine fairly sane, although from a purely
paranoid perspective I can see a few things I would need to look
at more to be certain they are safe.

Eric