Re: [PATCH] x86: Fix static_key in load_mm_cr4()

[Mikulas Patocka]

On Thu, 9 Jul 2015, Peter Zijlstra wrote:

> 
> Mikulas reported his K6-3 not booting. This is because the static_key
> confusion struck and bit Andy, this wants to be static_key_false().
> 
> Fixes: a66734297f78 ("perf/x86: Add /sys/devices/cpu/rdpmc=2 to allow rdpmc for all tasks")
> Cc: Andy Lutomirski <luto@xxxxxxxxxxxxxx>
> Reported-by: Mikulas Patocka <mpatocka@xxxxxxxxxx>
> Tested-by: Mikulas Patocka <mpatocka@xxxxxxxxxx>
> Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>


You should also add
Cc: stable@xxxxxxxxxxxxxxx	# v4.0
so that it will be backported to 4.0 and 4.1.

> ---
>  arch/x86/include/asm/mmu_context.h | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/arch/x86/include/asm/mmu_context.h b/arch/x86/include/asm/mmu_context.h
> index 5e8daee7c5c9..804a3a6030ca 100644
> --- a/arch/x86/include/asm/mmu_context.h
> +++ b/arch/x86/include/asm/mmu_context.h
> @@ -23,7 +23,7 @@ extern struct static_key rdpmc_always_available;
>  
>  static inline void load_mm_cr4(struct mm_struct *mm)
>  {
> -	if (static_key_true(&rdpmc_always_available) ||
> +	if (static_key_false(&rdpmc_always_available) ||
>  	    atomic_read(&mm->context.perf_rdpmc_allowed))
>  		cr4_set_bits(X86_CR4_PCE);
>  	else
> 
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