linux-kernel - Re: [BUGFIX/x86] Fix initialization of wakeup

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Date:	Wed, 11 Feb 2009 10:46:59 +0100
From:	Ingo Molnar <mingo@...e.hu>
To:	Alok Kataria <akataria@...are.com>
Cc:	Yinghai Lu <yinghai@...nel.org>,
	the arch/x86 maintainers <x86@...nel.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [BUGFIX/x86] Fix initialization of wakeup_cpu.


* Alok Kataria <akataria@...are.com> wrote:

> On Tue, 2009-02-10 at 16:31 -0800, Yinghai Lu wrote:
> > > 
> > >> 2. also will break 64 bit....
> > > isn't the default_x86_quirks defined for 64 bit too ? 
> > > 
> > 64 bit doesn't have genapic_apic_probe()
> > 
> > need to change that to 
> > #ifdef CONFIG_X86_32
> > 	genapic_apic_probe();
> > #endif
> > 
> 
> Ok here it is. 
> --
> 
> With refactoring of wake_cpu macros the 32bit code in tip doesn't 
> execute generic_apic_probe if CONFIG_X86_32_NON_STANDARD is not set.
> 
> Even on a x86 STANDARD cpu we need to execute the generic_apic_probe
> function, as we rely on this function to execute the update_genapic
> quirk which initilizes apic->wakeup_cpu. 
> 
> Failing to do so results in we making a call to a null function in do_boot_cpu.
> 
> The stack trace without the patch goes like this.
> 
> Booting processor 1 APIC 0x1 ip 0x6000
> BUG: unable to handle kernel NULL pointer dereference at (null)
> IP: [<(null)>] (null)
> *pdpt = 0000000000839001 *pde = 0000000000c97067 *pte = 0000000000000163 
> Oops: 0000 [#1] SMP 
> last sysfs file: 
> Modules linked in:
> 
> Pid: 1, comm: swapper Not tainted (2.6.29-rc4-tip #18) VMware Virtual Platform
> EIP: 0062:[<00000000>] EFLAGS: 00010293 CPU: 0
> EIP is at 0x0
> EAX: 00000001 EBX: 00006000 ECX: c077ed00 EDX: 00006000
> ESI: 00000001 EDI: 00000001 EBP: ef04cf40 ESP: ef04cf1c
>  DS: 007b ES: 007b FS: 00d8 GS: 0000 SS: 006a
> Process swapper (pid: 1, ti=ef04c000 task=ef050000 task.ti=ef04c000)
> Stack:
>  c0644e52 00000000 ef04cf24 ef04cf24 c064468d c0886dc0 00000000 c0702aea
>  ef055480 00000001 00000101 dead4ead ffffffff ffffffff c08af530 00000000
>  c0709715 ef04cf60 ef04cf60 00000001 00000000 00000000 dead4ead ffffffff
> Call Trace:
>  [<c0644e52>] ? native_cpu_up+0x2de/0x45b
>  [<c064468d>] ? do_fork_idle+0x0/0x19
>  [<c0645c5e>] ? _cpu_up+0x88/0xe8
>  [<c0645d20>] ? cpu_up+0x42/0x4e
>  [<c07e7462>] ? kernel_init+0x99/0x14b
>  [<c07e73c9>] ? kernel_init+0x0/0x14b
>  [<c040375f>] ? kernel_thread_helper+0x7/0x10
> Code:  Bad EIP value.
> EIP: [<00000000>] 0x0 SS:ESP 006a:ef04cf1c
> 
> I think we should call generic_apic_probe unconditionally for 32 bit now.
> 
> Signed-off-by: Alok N Kataria <akataria@...are.com>
> Cc: Yinghai Lu <yinghai@...nel.org>
> 
> Index: linux-tip-master/arch/x86/kernel/setup.c
> ===================================================================
> --- linux-tip-master.orig/arch/x86/kernel/setup.c	2009-02-10 12:05:18.000000000 -0800
> +++ linux-tip-master/arch/x86/kernel/setup.c	2009-02-10 16:37:59.000000000 -0800
> @@ -936,7 +936,7 @@
>  	map_vsyscall();
>  #endif
>  
> -#if defined(CONFIG_X86_32_NON_STANDARD) || defined(CONFIG_X86_BIGSMP)
> +#ifdef CONFIG_X86_32
>  	generic_apic_probe();
>  #endif

Please extend 64-bit with generic_apic_probe() instead. (and please also
make sure your patches build on a 64-bit defconfig)

	Ingo
--
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