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

[Vivek Goyal <vgoyal@in.ibm.com>]

On Fri, Nov 18, 2005 at 02:52:33PM -0700, Eric W. Biederman wrote:
> 
> > 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. 
> 

Hi Eric,

Initially we had written the patch without disable_local_APIC and
disable_IO_APIC only. But realized later that fix provided by you to
move apic initialization in init_IRQ has not been merged yet.

Like i386, here also this is a stop gap solution only till your patch is
merged. After that we shall drop this code.

I understand that it is less reliable but at least it provides us a base
to move forward and test kdump on x86_64 and address the other issues.

Thanks
Vivek