Re: [PATCH v2 18/58] i386/tdx: Validate TD attributes

[Daniel P . Berrangé]

On Fri, Aug 18, 2023 at 05:50:01AM -0400, Xiaoyao Li wrote:
> Validate TD attributes with tdx_caps that fixed-0 bits must be zero and
> fixed-1 bits must be set.
> 
> Besides, sanity check the attribute bits that have not been supported by
> QEMU yet. e.g., debug bit, it will be allowed in the future when debug
> TD support lands in QEMU.
> 
> Signed-off-by: Xiaoyao Li <xiaoyao.li@intel.com>
> Acked-by: Gerd Hoffmann <kraxel@redhat.com>
> ---
>  target/i386/kvm/tdx.c | 27 +++++++++++++++++++++++++--
>  1 file changed, 25 insertions(+), 2 deletions(-)
> 
> diff --git a/target/i386/kvm/tdx.c b/target/i386/kvm/tdx.c
> index 629abd267da8..73da15377ec3 100644
> --- a/target/i386/kvm/tdx.c
> +++ b/target/i386/kvm/tdx.c
> @@ -32,6 +32,7 @@
>                                       (1U << KVM_FEATURE_PV_SCHED_YIELD) | \
>                                       (1U << KVM_FEATURE_MSI_EXT_DEST_ID))
>  
> +#define TDX_TD_ATTRIBUTES_DEBUG             BIT_ULL(0)
>  #define TDX_TD_ATTRIBUTES_SEPT_VE_DISABLE   BIT_ULL(28)
>  #define TDX_TD_ATTRIBUTES_PKS               BIT_ULL(30)
>  #define TDX_TD_ATTRIBUTES_PERFMON           BIT_ULL(63)
> @@ -462,13 +463,32 @@ int tdx_kvm_init(MachineState *ms, Error **errp)
>      return 0;
>  }
>  
> -static void setup_td_guest_attributes(X86CPU *x86cpu)
> +static int tdx_validate_attributes(TdxGuest *tdx)
> +{
> +    if (((tdx->attributes & tdx_caps->attrs_fixed0) | 
> tdx_caps->attrs_fixed1) !=
> +        tdx->attributes) {
> +            error_report("Invalid attributes 0x%lx for TDX VM (fixed0 
> 0x%llx, fixed1 0x%llx)",
> +                          tdx->attributes, tdx_caps->attrs_fixed0, 
> tdx_caps->attrs_fixed1);
> +            return -EINVAL;
> +    }
> +
> +    if (tdx->attributes & TDX_TD_ATTRIBUTES_DEBUG) {
> +        error_report("Current QEMU doesn't support attributes.debug[bit 0] 
> for TDX VM");
> +        return -EINVAL;
> +    }

Use error_setg() in both cases, passing in a 'Error **errp' object,
and 'return -1' instead of returning an errno value.

> +
> +    return 0;
> +}
> +
> +static int setup_td_guest_attributes(X86CPU *x86cpu)
>  {
>      CPUX86State *env = &x86cpu->env;
>  
>      tdx_guest->attributes |= (env->features[FEAT_7_0_ECX] & 
> CPUID_7_0_ECX_PKS) ?
>                               TDX_TD_ATTRIBUTES_PKS : 0;
>      tdx_guest->attributes |= x86cpu->enable_pmu ? TDX_TD_ATTRIBUTES_PERFMON 
> : 0;
> +
> +    return tdx_validate_attributes(tdx_guest);

Pass along "errp" into this

>  }
>  
>  int tdx_pre_create_vcpu(CPUState *cpu)
> @@ -493,7 +513,10 @@ int tdx_pre_create_vcpu(CPUState *cpu)

In an earlier patch I suggested adding 'Error **errp' to this method...

>          goto out_free;
>      }
>  
> -    setup_td_guest_attributes(x86cpu);
> +    r = setup_td_guest_attributes(x86cpu);

...it can also be passed into this method

> +    if (r) {
> +        goto out;
> +    }
>  
>      init_vm->cpuid.nent = kvm_x86_arch_cpuid(env, init_vm->cpuid.entries, 0);
>      init_vm->attributes = tdx_guest->attributes;
> -- 
> 2.34.1
> 

With regards,
Daniel
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