Re: 4.12 REGRESSION, 4.12 does not boot as VirtualBox guest

[Hans de Goede <hdegoede@redhat.com>]

Hi,

On 12-06-17 13:52, Peter Zijlstra wrote:
> On Mon, Jun 12, 2017 at 10:16:53AM +0200, Thomas Gleixner wrote:
>> On Sat, 10 Jun 2017, Linus Torvalds wrote:
>>
>>> On Fri, Jun 9, 2017 at 3:33 AM, Hans de Goede <hdegoede@redhat.com> wrote:
>>>>
>>>> Sorry for escalating this right up to you, but this issue
>>>> does not seem to be getting any attention and I'm not sure
>>>> which subsys maintainer to poke about this.
>>>
>>> Looks like x86. Added people.
>>>
>>>> The problem is that the 4.12-rc# kernels fail to boot on
>>>> VirtualBox guests hosted on any machine with a Sky Lake
>>>> (and probably also a Kaby Lake) CPU, for details see:
>>>>
>>>> https://bugzilla.kernel.org/show_bug.cgi?id=195961
>>
>> Looks like the WARN/BUG rework. Peter????
> 
> I wasn't aware we'd call WARN _that_ early. Does something like so make
> it work?

Yes it does, with this patch the oops is back (unrelated problem) and
the kernel boots again :)

You can add my:

Tested-by: Hans de Goede <hdegoede@redhat.com>

Regards,

Hans



> 
> ---
>   arch/x86/include/asm/extable.h | 1 +
>   arch/x86/kernel/traps.c        | 2 +-
>   arch/x86/mm/extable.c          | 3 +++
>   3 files changed, 5 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/x86/include/asm/extable.h b/arch/x86/include/asm/extable.h
> index b8ad261d11dc..c66d19e3c23e 100644
> --- a/arch/x86/include/asm/extable.h
> +++ b/arch/x86/include/asm/extable.h
> @@ -29,6 +29,7 @@ struct pt_regs;
>   	} while (0)
>   
>   extern int fixup_exception(struct pt_regs *regs, int trapnr);
> +extern int fixup_bug(struct pt_regs *regs, int trapnr);
>   extern bool ex_has_fault_handler(unsigned long ip);
>   extern void early_fixup_exception(struct pt_regs *regs, int trapnr);
>   
> diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c
> index 3995d3a777d4..bf54309b85da 100644
> --- a/arch/x86/kernel/traps.c
> +++ b/arch/x86/kernel/traps.c
> @@ -182,7 +182,7 @@ int is_valid_bugaddr(unsigned long addr)
>   	return ud == INSN_UD0 || ud == INSN_UD2;
>   }
>   
> -static int fixup_bug(struct pt_regs *regs, int trapnr)
> +int fixup_bug(struct pt_regs *regs, int trapnr)
>   {
>   	if (trapnr != X86_TRAP_UD)
>   		return 0;
> diff --git a/arch/x86/mm/extable.c b/arch/x86/mm/extable.c
> index 35ea061010a1..0ea8afcb929c 100644
> --- a/arch/x86/mm/extable.c
> +++ b/arch/x86/mm/extable.c
> @@ -162,6 +162,9 @@ void __init early_fixup_exception(struct pt_regs *regs, int trapnr)
>   	if (fixup_exception(regs, trapnr))
>   		return;
>   
> +	if (fixup_bug(regs, trapnr))
> +		return;
> +
>   fail:
>   	early_printk("PANIC: early exception 0x%02x IP %lx:%lx error %lx cr2 0x%lx\n",
>   		     (unsigned)trapnr, (unsigned long)regs->cs, regs->ip,
>