linux-kernel - Re: [PATCH] random: Fix kernel panic due to system

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Date:   Mon, 19 Sep 2016 10:48:12 -0400
From:   Waiman Long <waiman.long@....com>
To:     Matt Fleming <matt@...eblueprint.co.uk>
CC:     Linus Torvalds <torvalds@...ux-foundation.org>,
        Theodore Ts'o <tytso@....edu>, Arnd Bergmann <arnd@...db.de>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Scott J Norton <scott.norton@....com>,
        Douglas Hatch <doug.hatch@....com>,
        Borislav Petkov <bp@...e.de>
Subject: Re: [PATCH] random: Fix kernel panic due to system_wq use before
 init

On 09/19/2016 08:43 AM, Matt Fleming wrote:
> On Sun, 18 Sep, at 11:09:08PM, Waiman Long wrote:
>> On 09/14/2016 03:19 PM, Linus Torvalds wrote:
>>> On Wed, Sep 14, 2016 at 12:14 PM, Waiman Long<waiman.long@....com>   wrote:
>>>> In the stack backtrace above, the kernel hadn't even reached SMP boot after
>>>> about 50s. That was extremely slow. I tried the 4.7.3 kernel and it booted
>>>> up fine. So I suspect that there may be too many interrupts going on and it
>>>> consumes most of the CPU cycles. The prime suspect is the random driver, I
>>>> think.
>>> Any chance of bisecting it at least partially? The random driver
>>> doesn't do interrupts itself, it just gets called by other drivers
>>> doing intterrupts. So if there are too many of them, that would be
>>> something else..
>>>
>>>                 Linus
>> I have finally finished bisecting the problem. I was wrong in saying that
>> the 4.7.3 kernel had no problem. It did have. There were some slight
>> differences between the 4.8 and 4.7 kernel config files that I used. After
>> some further testing, it was found that the bootup problem only happened
>> when the following kernel config option was defined:
>>
>> CONFIG_EFI_MIXED=y
>
> Could you try this patch? It won't be the final version, because it
> doesn't address the root cause of the crash, which looks like page
> table corruption of some kind, but it should at least confirm that
> this is the buggy code,
>
> ---
>
> diff --git a/arch/x86/platform/efi/efi_64.c b/arch/x86/platform/efi/efi_64.c
> index 677e29e29473..8dd3784eb075 100644
> --- a/arch/x86/platform/efi/efi_64.c
> +++ b/arch/x86/platform/efi/efi_64.c
> @@ -245,7 +245,7 @@ int __init efi_setup_page_tables(unsigned long pa_memmap, unsigned num_pages)
>   	 * text and allocate a new stack because we can't rely on the
>   	 * stack pointer being<  4GB.
>   	 */
> -	if (!IS_ENABLED(CONFIG_EFI_MIXED))
> +	if (!IS_ENABLED(CONFIG_EFI_MIXED) || efi_is_native())
>   		return 0;
>
>   	/*

With this patch applied, I am able to successfully boot both the 
16-socket 12-TB and 8-socket 6TB configurations without problem.

Tested-by: Waiman Long <Waiman.Long@....com>