Re: [PATCH V2 3/3] target/i386: Move host_cpu_enable_cpu_pm into kvm_cpu_realizefn()

[Zhao Liu]

On Fri, May 24, 2024 at 01:00:17PM -0700, Zide Chen wrote:
> Date: Fri, 24 May 2024 13:00:17 -0700
> From: Zide Chen <zide.chen@intel.com>
> Subject: [PATCH V2 3/3] target/i386: Move host_cpu_enable_cpu_pm into
>  kvm_cpu_realizefn()
> X-Mailer: git-send-email 2.34.1
> 
> It seems not a good idea to expand features in host_cpu_realizefn,
> which is for host CPU only. 

It is restricted by max_features and should be part of the "max" CPU,
and the current target/i386/host-cpu.c should only serve the “host” CPU.

> Additionally, cpu-pm option is KVM
> specific, and it's cleaner to put it in kvm_cpu_realizefn(), together
> with the WAITPKG code.
> 
> Fixes: f5cc5a5c1686 ("i386: split cpu accelerators from cpu.c, using 
> AccelCPUClass")
> Signed-off-by: Zide Chen <zide.chen@intel.com>
> ---
>  target/i386/host-cpu.c    | 12 ------------
>  target/i386/kvm/kvm-cpu.c | 11 +++++++++--
>  2 files changed, 9 insertions(+), 14 deletions(-)
> 
> diff --git a/target/i386/host-cpu.c b/target/i386/host-cpu.c
> index 280e427c017c..8b8bf5afeccf 100644
> --- a/target/i386/host-cpu.c
> +++ b/target/i386/host-cpu.c
> @@ -42,15 +42,6 @@ static uint32_t host_cpu_phys_bits(void)
>      return host_phys_bits;
>  }
>  
> -static void host_cpu_enable_cpu_pm(X86CPU *cpu)
> -{
> -    CPUX86State *env = &cpu->env;
> -
> -    host_cpuid(5, 0, &cpu->mwait.eax, &cpu->mwait.ebx,
> -               &cpu->mwait.ecx, &cpu->mwait.edx);
> -    env->features[FEAT_1_ECX] |= CPUID_EXT_MONITOR;
> -}
> -
>  static uint32_t host_cpu_adjust_phys_bits(X86CPU *cpu)
>  {
>      uint32_t host_phys_bits = host_cpu_phys_bits();
> @@ -83,9 +74,6 @@ bool host_cpu_realizefn(CPUState *cs, Error **errp)
>      X86CPU *cpu = X86_CPU(cs);
>      CPUX86State *env = &cpu->env;
>  
> -    if (cpu->max_features && enable_cpu_pm) {
> -        host_cpu_enable_cpu_pm(cpu);
> -    }
>      if (env->features[FEAT_8000_0001_EDX] & CPUID_EXT2_LM) {
>          uint32_t phys_bits = host_cpu_adjust_phys_bits(cpu);
>  
> diff --git a/target/i386/kvm/kvm-cpu.c b/target/i386/kvm/kvm-cpu.c
> index 3adcedf0dbc3..197c892da89a 100644
> --- a/target/i386/kvm/kvm-cpu.c
> +++ b/target/i386/kvm/kvm-cpu.c
> @@ -64,9 +64,16 @@ static bool kvm_cpu_realizefn(CPUState *cs, Error **errp)
>       *   cpu_common_realizefn() (via xcc->parent_realize)
>       */
>      if (cpu->max_features) {
> -        if (enable_cpu_pm && kvm_has_waitpkg()) {
> -            env->features[FEAT_7_0_ECX] |= CPUID_7_0_ECX_WAITPKG;
> +        if (enable_cpu_pm) {
> +            if (kvm_has_waitpkg()) {
> +                env->features[FEAT_7_0_ECX] |= CPUID_7_0_ECX_WAITPKG;
> +            }

If you agree with my comment in patch 2, here we need a mwait bit check.

> +            host_cpuid(5, 0, &cpu->mwait.eax, &cpu->mwait.ebx,
> +                       &cpu->mwait.ecx, &cpu->mwait.edx);
> +            env->features[FEAT_1_ECX] |= CPUID_EXT_MONITOR;
>          }
> +
>          if (cpu->ucode_rev == 0) {
>              cpu->ucode_rev =
>                  kvm_arch_get_supported_msr_feature(kvm_state,
> -- 
> 2.34.1
> 
>