Re: [Xen-devel] [PATCH] libxc: Expose the MPX cpuid flag to guest

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

On Mon, Jan 11, 2016 at 04:52:10PM +0800, Liang Li wrote:
> If hardware support memory protect externsion, expose this feature

extension
> to guest by default. Users don't have to use a 'cpuid= ' option in
> config file to turn it on.
> 
> Signed-off-by: Liang Li <liang.z.li@xxxxxxxxx>
> ---
>  tools/libxc/xc_cpufeature.h | 1 +
>  tools/libxc/xc_cpuid_x86.c  | 6 ++++++
>  2 files changed, 7 insertions(+)
> 
> diff --git a/tools/libxc/xc_cpufeature.h b/tools/libxc/xc_cpufeature.h
> index c3ddc80..cda9305 100644
> --- a/tools/libxc/xc_cpufeature.h
> +++ b/tools/libxc/xc_cpufeature.h
> @@ -137,6 +137,7 @@
>  #define X86_FEATURE_ERMS         9 /* Enhanced REP MOVSB/STOSB */
>  #define X86_FEATURE_INVPCID     10 /* Invalidate Process Context ID */
>  #define X86_FEATURE_RTM         11 /* Restricted Transactional Memory */
> +#define X86_FEATURE_MPX         14 /* Memory Protection Extensions */
>  #define X86_FEATURE_RDSEED      18 /* RDSEED instruction */
>  #define X86_FEATURE_ADX         19 /* ADCX, ADOX instructions */
>  #define X86_FEATURE_SMAP        20 /* Supervisor Mode Access Protection */
> diff --git a/tools/libxc/xc_cpuid_x86.c b/tools/libxc/xc_cpuid_x86.c
> index 8882c01..4c88db4 100644
> --- a/tools/libxc/xc_cpuid_x86.c
> +++ b/tools/libxc/xc_cpuid_x86.c
> @@ -423,6 +423,8 @@ static void xc_cpuid_hvm_policy(xc_interface *xch,
>                          bitmaskof(X86_FEATURE_ERMS) |
>                          bitmaskof(X86_FEATURE_INVPCID) |
>                          bitmaskof(X86_FEATURE_RTM)  |
> +                        ((info->xfeature_mask != 0) ?
> +                        bitmaskof(X86_FEATURE_MPX) : 0)  |
>                          bitmaskof(X86_FEATURE_RDSEED)  |
>                          bitmaskof(X86_FEATURE_ADX)  |
>                          bitmaskof(X86_FEATURE_SMAP) |
> @@ -538,6 +540,7 @@ static void xc_cpuid_pv_policy(xc_interface *xch,
>  
>      case 0x00000007:
>          if ( input[1] == 0 )
> +        {
>              regs[1] &= (bitmaskof(X86_FEATURE_BMI1) |
>                          bitmaskof(X86_FEATURE_HLE)  |
>                          bitmaskof(X86_FEATURE_AVX2) |
> @@ -547,6 +550,9 @@ static void xc_cpuid_pv_policy(xc_interface *xch,
>                          bitmaskof(X86_FEATURE_RDSEED)  |
>                          bitmaskof(X86_FEATURE_ADX)  |
>                          bitmaskof(X86_FEATURE_FSGSBASE));
> +            if ( info->xfeature_mask == 0 )
> +                clear_bit(X86_FEATURE_MPX, regs[1]);
> +        }
>          else
>              regs[1] = 0;
>          regs[0] = regs[2] = regs[3] = 0;
> -- 
> 1.9.1
> 
> 
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