[PATCH] x86: Fix Haswell strong flags (BZ#23709)

[Florian Weimer]

* Adhemerval Zanella:

> diff --git a/sysdeps/x86/cpu-features.c b/sysdeps/x86/cpu-features.c
> index f4e0f5a2ed..80b3054cf8 100644
> --- a/sysdeps/x86/cpu-features.c
> +++ b/sysdeps/x86/cpu-features.c
> @@ -316,7 +316,13 @@ init_cpu_features (struct cpu_features *cpu_features)
>  		    | bit_arch_Fast_Unaligned_Copy
>  		    | bit_arch_Prefer_PMINUB_for_stringop);
>  	      break;
> +	    }
>  
> +	 /* Disable TSX on some Haswell processors to avoid TSX on kernels that
> +	    weren't updated with the latest microcode package (which disables
> +	    broken feature by default).  */
> +	 switch (model)
> +	    {
>  	    case 0x3f:
>  	      /* Xeon E7 v3 with stepping >= 4 has working TSX.  */
>  	      if (stepping >= 4)

I think the change is okay as posted.  It will need some testing in the
field because the newly selected implementations could have unexpected
performance drawbacks.

Thanks,
Florian