Re: [PATCH 06/21] target/i386/cpu: Pass Error** to x86_cpu_filter_features()

["Daniel P. Berrangé" <berrange@redhat.com>]

On Thu, Jan 16, 2025 at 12:22:32AM +0100, Philippe Mathieu-Daudé wrote:
> Simplify x86_cpu_realizefn() by passing an Error**
> argument to x86_cpu_filter_features().
> 
> Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
> ---
>  target/i386/cpu.c | 26 +++++++++-----------------
>  1 file changed, 9 insertions(+), 17 deletions(-)
> 
> diff --git a/target/i386/cpu.c b/target/i386/cpu.c
> index 42227643126..c48241fb902 100644
> --- a/target/i386/cpu.c
> +++ b/target/i386/cpu.c
> @@ -5896,7 +5896,7 @@ static void x86_cpu_parse_featurestr(const char *typename, char *features,
>      }
>  }
>  
> -static bool x86_cpu_filter_features(X86CPU *cpu, bool verbose);
> +static bool x86_cpu_filter_features(X86CPU *cpu, Error **errp);
>  
>  /* Build a list with the name of all features on a feature word array */
>  static void x86_cpu_list_feature_names(FeatureWordArray features,
> @@ -6084,7 +6084,7 @@ static void x86_cpu_class_check_missing_features(X86CPUClass *xcc,
>          error_free(err);
>      }
>  
> -    x86_cpu_filter_features(xc, false);
> +    x86_cpu_filter_features(xc, NULL);
>  
>      x86_cpu_list_feature_names(xc->filtered_features, tail);
>  
> @@ -7650,7 +7650,7 @@ void x86_cpu_expand_features(X86CPU *cpu, Error **errp)
>   *
>   * Returns: true if any flag is not supported by the host, false otherwise.
>   */
> -static bool x86_cpu_filter_features(X86CPU *cpu, bool verbose)
> +static bool x86_cpu_filter_features(X86CPU *cpu, Error **errp)
>  {
>      CPUX86State *env = &cpu->env;
>      FeatureWord w;
> @@ -7660,7 +7660,7 @@ static bool x86_cpu_filter_features(X86CPU *cpu, bool verbose)
>      uint32_t eax_0, ebx_0, ecx_0, edx_0;
>      uint32_t eax_1, ebx_1, ecx_1, edx_1;
>  
> -    if (verbose) {
> +    if (errp) {
>          prefix = accel_uses_host_cpuid()
>                   ? "host doesn't support requested feature"
>                   : "TCG doesn't support requested feature";
> @@ -7712,15 +7712,13 @@ static bool x86_cpu_filter_features(X86CPU *cpu, bool verbose)
>          uint8_t version = ebx_0 & 0xff;
>  
>          if (version < env->avx10_version) {
> -            if (prefix) {
> -                warn_report("%s: avx10.%d. Adjust to avx10.%d",
> -                            prefix, env->avx10_version, version);
> -            }
> +            error_setg(errp, "%s: avx10.%d. Adjust to avx10.%d",
> +                       prefix, env->avx10_version, version);
>              env->avx10_version = version;
>              have_filtered_features = true;

This doesn't look right.  Previously it was correct to carry on and
set  'env->avx10_version = version' or 'have_filtered_features',
because it was upto the caller whether this was an error scenario
or just a warning.

With your change though, we're unambiguously treating this as an
error condition. So we should return from this method immediately
after calling 'error_setg' now.

>          }
>      } else if (env->avx10_version && prefix) {
> -        warn_report("%s: avx10.%d.", prefix, env->avx10_version);
> +        error_setg(errp, "%s: avx10.%d.", prefix, env->avx10_version);
>          have_filtered_features = true;

Same here, needs a 'return'

>      }
>  
> @@ -7822,14 +7820,8 @@ static void x86_cpu_realizefn(DeviceState *dev, Error **errp)
>          }
>      }
>  
> -    if (x86_cpu_filter_features(cpu, cpu->enforce_cpuid)) {
> -        if (cpu->enforce_cpuid) {
> -            error_setg(&local_err,
> -                       accel_uses_host_cpuid() ?
> -                       "Host doesn't support requested features" :
> -                       "TCG doesn't support requested features");
> -            goto out;
> -        }
> +    if (x86_cpu_filter_features(cpu, cpu->enforce_cpuid ? &local_err : NULL)) {
> +        goto out;
>      }
>  
>      /* On AMD CPUs, some CPUID[8000_0001].EDX bits must match the bits on
> -- 
> 2.47.1
> 
> 

With regards,
Daniel
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