Re: invalidate caches before going into suspend

[Ingo Molnar <mingo@elte.hu>]

* Mark Langsdorf <mark.langsdorf@amd.com> wrote:

> When a CPU core is shut down, all of its caches need to be flushed to 
> prevent stale data from causing errors if the core is resumed. Current 
> Linux suspend code performs an assignment after the flush, which can 
> add dirty data back to the cache.  On some AMD platforms, additional 
> speculative reads have caused crashes on resume because of this dirty 
> data.
> 
> Relocate the cache flush to be the very last thing done before 
> halting.

nice catch! Applied to x86/urgent.

I'm really curious: how did you find this bug? Did you see a CPU come up 
as !CPU_DEAD?

> Signed-off-by: Mark Langsdorf <mark.langsdorf@amd.com>
> Acked-by: Mark Borden <mark.borden@amd.com>
> Acked-by: Michael Hohmuth <michael.hohmuth@amd.com>
> 
> diff -r f3f819497a68 arch/x86/kernel/process_64.c
> --- a/arch/x86/kernel/process_64.c	Thu Aug 07 04:24:53 2008 -0500
> +++ b/arch/x86/kernel/process_64.c	Tue Aug 12 07:11:36 2008 -0500
> @@ -93,11 +93,11 @@ static inline void play_dead(void)
>  static inline void play_dead(void)
>  {
>  	idle_task_exit();
> -	wbinvd();
>  	mb();
>  	/* Ack it */
>  	__get_cpu_var(cpu_state) = CPU_DEAD;
>  
> +	wbinvd();
>  	local_irq_disable();
>  	while (1)
>  		halt();

please send a patch for the 32-bit side too, it has the same bug.

also, we might be safer if the wbinvd(), the CLI and the halt was in a 
single assembly sequence:

	if (cpu >= i486)
		asm ("cli; wbinvd; cli; 1: hlt; jmp 1b")
	else
		asm ("cli; 1: hlt; jmp 1b")

to make sure the compiler doesnt ever insert something into this 
codepath? [ And note the double cli which would be further 
robustification - in theory we could get a spurious interrupt straight 
after the wbinvd. ] Hm?

	Ingo