Re: [Xen-devel] [PATCH V5 6/6] x86/hvm: pkeys, add pkeys support for cpuid handling

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 22.12.15 at 11:30, <huaitong.han@xxxxxxxxx> wrote:
> This patch adds pkeys support for cpuid handing.
> 
> Pkeys hardware support is CPUID.7.0.ECX[3]:PKU. software support is
> CPUID.7.0.ECX[4]:OSPKE and it reflects the support setting of CR4.PKE.
> 
> Signed-off-by: Huaitong Han <huaitong.han@xxxxxxxxx>
> ---
>  tools/libxc/xc_cpufeature.h |  2 ++
>  tools/libxc/xc_cpuid_x86.c  |  6 ++++--
>  xen/arch/x86/hvm/hvm.c      | 36 +++++++++++++++++++++++-------------
>  3 files changed, 29 insertions(+), 15 deletions(-)
> 
> diff --git a/tools/libxc/xc_cpufeature.h b/tools/libxc/xc_cpufeature.h
> index c3ddc80..f6a9778 100644
> --- a/tools/libxc/xc_cpufeature.h
> +++ b/tools/libxc/xc_cpufeature.h
> @@ -141,5 +141,7 @@
>  #define X86_FEATURE_ADX         19 /* ADCX, ADOX instructions */
>  #define X86_FEATURE_SMAP        20 /* Supervisor Mode Access Protection */
>  
> +/* Intel-defined CPU features, CPUID level 0x00000007:0 (ecx) */
> +#define X86_FEATURE_PKU     3
>  
>  #endif /* __LIBXC_CPUFEATURE_H */
> diff --git a/tools/libxc/xc_cpuid_x86.c b/tools/libxc/xc_cpuid_x86.c
> index 8882c01..1ce979b 100644
> --- a/tools/libxc/xc_cpuid_x86.c
> +++ b/tools/libxc/xc_cpuid_x86.c
> @@ -427,9 +427,11 @@ static void xc_cpuid_hvm_policy(xc_interface *xch,
>                          bitmaskof(X86_FEATURE_ADX)  |
>                          bitmaskof(X86_FEATURE_SMAP) |
>                          bitmaskof(X86_FEATURE_FSGSBASE));
> +            regs[2] &= bitmaskof(X86_FEATURE_PKU);
>          } else
> -            regs[1] = 0;
> -        regs[0] = regs[2] = regs[3] = 0;
> +            regs[1] = regs[2] = 0;
> +
> +        regs[0] = regs[3] = 0;
>          break;
>  
>      case 0x0000000d:
> diff --git a/xen/arch/x86/hvm/hvm.c b/xen/arch/x86/hvm/hvm.c
> index 59916ed..076313b 100644
> --- a/xen/arch/x86/hvm/hvm.c
> +++ b/xen/arch/x86/hvm/hvm.c
> @@ -4572,7 +4572,7 @@ void hvm_cpuid(unsigned int input, unsigned int *eax, 
> unsigned int *ebx,
>              __clear_bit(X86_FEATURE_APIC & 31, edx);
>  
>          /* Fix up OSXSAVE. */
> -        if ( cpu_has_xsave )
> +        if ( *ecx & cpufeat_mask(X86_FEATURE_XSAVE) )
>              *ecx |= (v->arch.hvm_vcpu.guest_cr[4] & X86_CR4_OSXSAVE) ?
>                       cpufeat_mask(X86_FEATURE_OSXSAVE) : 0;
>  
> @@ -4585,21 +4585,31 @@ void hvm_cpuid(unsigned int input, unsigned int *eax, 
> unsigned int *ebx,
>              *edx &= ~cpufeat_mask(X86_FEATURE_PSE36);
>          break;
>      case 0x7:
> -        if ( (count == 0) && !cpu_has_smep )
> -            *ebx &= ~cpufeat_mask(X86_FEATURE_SMEP);
> +        if ( count == 0 )
> +        {
> +            if ( !cpu_has_smep )
> +                *ebx &= ~cpufeat_mask(X86_FEATURE_SMEP);
>  
> -        if ( (count == 0) && !cpu_has_smap )
> -            *ebx &= ~cpufeat_mask(X86_FEATURE_SMAP);
> +            if ( !cpu_has_smap )
> +                *ebx &= ~cpufeat_mask(X86_FEATURE_SMAP);
>  
> -        /* Don't expose MPX to hvm when VMX support is not available */
> -        if ( (count == 0) &&
> -             (!(vmx_vmexit_control & VM_EXIT_CLEAR_BNDCFGS) ||
> -              !(vmx_vmentry_control & VM_ENTRY_LOAD_BNDCFGS)) )
> -            *ebx &= ~cpufeat_mask(X86_FEATURE_MPX);
> +            /* Don't expose MPX to hvm when VMX support is not available */

Please fix the comment style if you touch this anyway.

> +            if (!(vmx_vmexit_control & VM_EXIT_CLEAR_BNDCFGS) ||
> +                  !(vmx_vmentry_control & VM_ENTRY_LOAD_BNDCFGS))
> +                *ebx &= ~cpufeat_mask(X86_FEATURE_MPX);
>  
> -        /* Don't expose INVPCID to non-hap hvm. */
> -        if ( (count == 0) && !hap_enabled(d) )
> -            *ebx &= ~cpufeat_mask(X86_FEATURE_INVPCID);
> +            if ( !hap_enabled(d) )
> +            {
> +                /* Don't expose INVPCID to non-hap hvm. */
> +                *ebx &= ~cpufeat_mask(X86_FEATURE_INVPCID);
> +                /* X86_FEATURE_PKU is not yet implemented for shadow paging. 
> */
> +                *ecx &= ~cpufeat_mask(X86_FEATURE_PKU);
> +            }
> +
> +            if ( *ecx & cpufeat_mask(X86_FEATURE_PKU))
> +                *ecx |= (v->arch.hvm_vcpu.guest_cr[4] & X86_CR4_PKE) ?
> +                         cpufeat_mask(X86_FEATURE_OSPKE) : 0;

Bogus use of ?: considering that you or in zero in its "false" case.
Just extend the if() condition.

Jan

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