Re: [Xen-devel] [PATCH] x86: cap address bits CPUID output

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

On 02/05/16 16:11, Jan Beulich wrote:
> --- a/xen/arch/x86/e820.c
> +++ b/xen/arch/x86/e820.c
> @@ -451,11 +451,11 @@ static uint64_t __init mtrr_top_of_ram(v
>           return 0;
>  
>      /* Find the physical address size for this CPU. */
> -    cpuid(0x80000000, &eax, &ebx, &ecx, &edx);
> -    if ( eax >= 0x80000008 )
> +    if ( cpuid_eax(0x80000000) >= 0x80000008 )

You indicated in review of my cpuid series that this check is buggy, and
the upper half needs comparing exactly to 0x8000.

It occurs to me that early_cpu_detect() really should be callled
earlier, to avoid needing to recalculate this information.

~Andrew

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