Re: [Xen-devel] [PATCH v2 1/2] xc_cpuid_x86.c: Simplify masking conditions and remove redundant work

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 09.09.14 at 06:31, <alfred.z.song@xxxxxxxxx> wrote:
> @@ -195,16 +186,14 @@ static void intel_xc_cpuid_policy(
>          break;
>  
>      case 0x80000001: {
> -        int is_64bit = hypervisor_is_64bit(xch) && is_pae;
> -
>          /* Only a few features are advertised in Intel's 0x80000001. */
> -        regs[2] &= (is_64bit ? bitmaskof(X86_FEATURE_LAHF_LM) : 0) |
> -                               bitmaskof(X86_FEATURE_3DNOWPREFETCH) |
> -                               bitmaskof(X86_FEATURE_ABM);
> -        regs[3] &= ((is_pae ? bitmaskof(X86_FEATURE_NX) : 0) |
> -                    (is_64bit ? bitmaskof(X86_FEATURE_LM) : 0) |
> -                    (is_64bit ? bitmaskof(X86_FEATURE_SYSCALL) : 0) |
> -                    (is_64bit ? bitmaskof(X86_FEATURE_RDTSCP) : 0));
> +        regs[2] &= (bitmaskof(X86_FEATURE_LAHF_LM) |
> +                    bitmaskof(X86_FEATURE_3DNOWPREFETCH) |
> +                    bitmaskof(X86_FEATURE_ABM);
> +        regs[3] &= (bitmaskof(X86_FEATURE_NX) |
> +                    bitmaskof(X86_FEATURE_LM) |
> +                    (is_pae ? bitmaskof(X86_FEATURE_SYSCALL) : 0) |
> +                    (is_pae ? bitmaskof(X86_FEATURE_RDTSCP) : 0));

As said before, tying these two features to is_pae seems a
little strange, but if the tools maintainers can live with that, I
guess I can too (short of having a better suggestion other
than to drop the conditionals altogether).

Jan


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