Re: [Xen-devel] [PATCH] tools/libxc: Properly increment ApicIdCoreSize field on AMD

[Wei Liu <wei.liu2@xxxxxxxxxx>]

On Fri, Jul 22, 2016 at 01:14:01PM -0400, Boris Ostrovsky wrote:
> Current code incorrectly adds 1 to full register instead of
> incrementing the field in bits 15:12.
> 
> Signed-off-by: Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>

Acked-by: Wei Liu <wei.liu2@xxxxxxxxxx>

I trust your expertise in this field. :-)

> ---
>  tools/libxc/xc_cpuid_x86.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/tools/libxc/xc_cpuid_x86.c b/tools/libxc/xc_cpuid_x86.c
> index 84f4e08..fbbac9e 100644
> --- a/tools/libxc/xc_cpuid_x86.c
> +++ b/tools/libxc/xc_cpuid_x86.c
> @@ -331,7 +331,8 @@ static void amd_xc_cpuid_policy(xc_interface *xch,
>           * ECX[15:12] is ApicIdCoreSize: ECX[7:0] is NumberOfCores (minus 
> one).
>           * Update to reflect vLAPIC_ID = vCPU_ID * 2.
>           */
> -        regs[2] = ((regs[2] & 0xf000u) + 1) | ((regs[2] & 0xffu) << 1) | 1u;
> +        regs[2] = ((regs[2] + (1u << 12)) & 0xf000u) |
> +                  ((regs[2] & 0xffu) << 1) | 1u;
>          break;
>  
>      case 0x8000000a: {
> -- 
> 1.8.3.1
> 

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