Re: [Xen-devel] [PATCH 2/3] xen/x86: Query for paddr_bits in early_cpu_detect()

[Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>]

On Mon, Nov 02, 2015 at 05:59:44PM +0000, Andrew Cooper wrote:
> It is __read_mostly, so repeatedly writing to it is suboptiomal.  As the
> MTRRs have already been set up, nothing good will come from its value
> changing across CPUs.

Reviewed-by: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
> 
> Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
> ---
> CC: Jan Beulich <JBeulich@xxxxxxxx>
> ---
>  xen/arch/x86/cpu/common.c | 5 +++--
>  1 file changed, 3 insertions(+), 2 deletions(-)
> 
> diff --git a/xen/arch/x86/cpu/common.c b/xen/arch/x86/cpu/common.c
> index 02f2504..ac8a258 100644
> --- a/xen/arch/x86/cpu/common.c
> +++ b/xen/arch/x86/cpu/common.c
> @@ -207,6 +207,9 @@ static void __init early_cpu_detect(void)
>       /* Leaf 0x1 capabilities filled in early for Xen. */
>       c->x86_capability[cpufeat_word(X86_FEATURE_FPU)] = cap0;
>       c->x86_capability[cpufeat_word(X86_FEATURE_XMM3)] = cap4;
> +
> +     if ( cpuid_eax(0x80000000) >= 0x80000008 )
> +             paddr_bits = cpuid_eax(0x80000008) & 0xff;
>  }
>  
>  static void __cpuinit generic_identify(struct cpuinfo_x86 *c)
> @@ -254,8 +257,6 @@ static void __cpuinit generic_identify(struct cpuinfo_x86 
> *c)
>               }
>               if ( c->extended_cpuid_level >= 0x80000004 )
>                       get_model_name(c); /* Default name */
> -             if ( c->extended_cpuid_level >= 0x80000008 )
> -                     paddr_bits = cpuid_eax(0x80000008) & 0xff;
>       }
>  
>       /* Might lift BIOS max_leaf=3 limit. */
> -- 
> 2.1.4
> 
> 
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> http://lists.xen.org/xen-devel

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