Re: [PATCH] microvm: do not use the lastest cpu version

[Igor Mammedov <imammedo@redhat.com>]

On Thu, 13 Feb 2025 15:11:00 +0530
Ani Sinha <anisinha@redhat.com> wrote:

> Microvm machines are not versioned and therefore there is no requirement to use
> the latest cpu model by default. Let microvms use the non-versioned cpu model.
> Those users who need spefific cpu versions can use explicit commandline to
> select the cpu version desired.

Above says why we can do this but,
I'd also add here a reason why we are doing that to begin with. 

> 
> CC: imammedo@redhat.com
> CC: zhao1.liu@intel.com
> Signed-off-by: Ani Sinha <anisinha@redhat.com>

Reviewed-by: Igor Mammedov <imammedo@redhat.com>

> ---
>  hw/i386/microvm.c |  2 +-
>  target/i386/cpu.c | 15 ---------------
>  target/i386/cpu.h |  4 ----
>  3 files changed, 1 insertion(+), 20 deletions(-)
> 
> Pipeline passes:
> https://gitlab.com/anisinha/qemu/-/pipelines/1669159835
> See also Igor's comment on
> https://patchwork.ozlabs.org/project/qemu-devel/patch/20250128035526.3750043-1-anisinha@redhat.com/
> 
> diff --git a/hw/i386/microvm.c b/hw/i386/microvm.c
> index a8d354aabe..b8be1542ff 100644
> --- a/hw/i386/microvm.c
> +++ b/hw/i386/microvm.c
> @@ -458,7 +458,7 @@ static void microvm_machine_state_init(MachineState *machine)
>  
>      microvm_memory_init(mms);
>  
> -    x86_cpus_init(x86ms, CPU_VERSION_LATEST);
> +    x86_cpus_init(x86ms, 1);
>  
>      microvm_devices_init(mms);
>  }
> diff --git a/target/i386/cpu.c b/target/i386/cpu.c
> index b5dd60d281..6d251c0025 100644
> --- a/target/i386/cpu.c
> +++ b/target/i386/cpu.c
> @@ -5513,18 +5513,6 @@ void x86_cpu_set_default_version(X86CPUVersion version)
>      default_cpu_version = version;
>  }
>  
> -static X86CPUVersion x86_cpu_model_last_version(const X86CPUModel *model)
> -{
> -    int v = 0;
> -    const X86CPUVersionDefinition *vdef =
> -        x86_cpu_def_get_versions(model->cpudef);
> -    while (vdef->version) {
> -        v = vdef->version;
> -        vdef++;
> -    }
> -    return v;
> -}
> -
>  /* Return the actual version being used for a specific CPU model */
>  static X86CPUVersion x86_cpu_model_resolve_version(const X86CPUModel *model)
>  {
> @@ -5532,9 +5520,6 @@ static X86CPUVersion x86_cpu_model_resolve_version(const X86CPUModel *model)
>      if (v == CPU_VERSION_AUTO) {
>          v = default_cpu_version;
>      }
> -    if (v == CPU_VERSION_LATEST) {
> -        return x86_cpu_model_last_version(model);
> -    }
>      return v;
>  }
>  
> diff --git a/target/i386/cpu.h b/target/i386/cpu.h
> index c67b42d34f..71f150a05f 100644
> --- a/target/i386/cpu.h
> +++ b/target/i386/cpu.h
> @@ -2701,10 +2701,6 @@ void apic_handle_tpr_access_report(DeviceState *d, target_ulong ip,
>                                     TPRAccess access);
>  
>  /* Special values for X86CPUVersion: */
> -
> -/* Resolve to latest CPU version */
> -#define CPU_VERSION_LATEST -1
> -
>  /*
>   * Resolve to version defined by current machine type.
>   * See x86_cpu_set_default_version()