Re: [Qemu-devel PATCH] target/i386: define a new MSR based feature word - FEAT_PERF_CAPABILITIES

[Paolo Bonzini]

On 29/05/20 09:43, Like Xu wrote:
> +        if (!cpu->enable_pmu) {
> +            *ecx &= ~CPUID_EXT_PDCM;
> +        }
>          break;
>      case 2:
>          /* cache info: needed for Pentium Pro compatibility */
> @@ -6505,6 +6528,12 @@ static void x86_cpu_realizefn(DeviceState *dev, Error **errp)
>          }
>      }
>  
> +    if (kvm_enabled() && cpu->enable_pmu &&
> +        (kvm_arch_get_supported_cpuid(kvm_state, 1, 0, R_ECX) &
> +         CPUID_EXT_PDCM)) {
> +        env->features[FEAT_1_ECX] |= CPUID_EXT_PDCM;
> +    }
> +

I'm dropping this hunk two hunks because it's going to break live
migration with e.g. "-cpu IvyBridge,pmu=on".  We will have to add PDCM
by default only to future CPU models, but "-cpu host,pmu=on" will pick
it up automatically.

Paolo