Re: [PATCH v4 04/19] target/i386/cpu: Remove X86CPU::check_cpuid field

[Xiaoyao Li <xiaoyao.li@intel.com>]

On 5/12/2025 4:39 PM, Philippe Mathieu-Daudé wrote:
> The X86CPU::check_cpuid boolean was only set in the
> pc_compat_2_4[] array, via the 'check=off' property.
> We removed all machines using that array, lets remove
> that CPU property and simplify x86_cpu_realizefn().

No.

We cannot do this. Because it changes the behavior of QEMU.

'check_cpuid' is true by default while 'enforce_cpuid' is false. So that 
QEMU emits warnings in x86_cpu_filter_features() by default when user 
requests unsupported CPU features. If remove "check" property and the 
internal 'check_cpuid', QEMU will not do it unless user sets 
enforce_cpuid explicitly.

> Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
> Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
> Reviewed-by: Zhao Liu <zhao1.liu@intel.com>
> ---
>   target/i386/cpu.h | 1 -
>   target/i386/cpu.c | 3 +--
>   2 files changed, 1 insertion(+), 3 deletions(-)
> 
> diff --git a/target/i386/cpu.h b/target/i386/cpu.h
> index 4f8ed8868e9..0db70a70439 100644
> --- a/target/i386/cpu.h
> +++ b/target/i386/cpu.h
> @@ -2164,7 +2164,6 @@ struct ArchCPU {
>       uint8_t hyperv_ver_id_sb;
>       uint32_t hyperv_ver_id_sn;
>   
> -    bool check_cpuid;
>       bool enforce_cpuid;
>       /*
>        * Force features to be enabled even if the host doesn't support them.
> diff --git a/target/i386/cpu.c b/target/i386/cpu.c
> index 1ca6307c72e..cd4361b4227 100644
> --- a/target/i386/cpu.c
> +++ b/target/i386/cpu.c
> @@ -8174,7 +8174,7 @@ static void x86_cpu_realizefn(DeviceState *dev, Error **errp)
>           }
>       }
>   
> -    if (x86_cpu_filter_features(cpu, cpu->check_cpuid || cpu->enforce_cpuid)) {
> +    if (x86_cpu_filter_features(cpu, cpu->enforce_cpuid)) {
>           if (cpu->enforce_cpuid) {
>               error_setg(&local_err,
>                          accel_uses_host_cpuid() ?
> @@ -8813,7 +8813,6 @@ static const Property x86_cpu_properties[] = {
>       DEFINE_PROP_UINT8("hv-version-id-sbranch", X86CPU, hyperv_ver_id_sb, 0),
>       DEFINE_PROP_UINT32("hv-version-id-snumber", X86CPU, hyperv_ver_id_sn, 0),
>   
> -    DEFINE_PROP_BOOL("check", X86CPU, check_cpuid, true),
>       DEFINE_PROP_BOOL("enforce", X86CPU, enforce_cpuid, false),
>       DEFINE_PROP_BOOL("x-force-features", X86CPU, force_features, false),
>       DEFINE_PROP_BOOL("kvm", X86CPU, expose_kvm, true),