Re: [Qemu-devel] [RFC 02/12] target-i386: Don't set any KVM flag by default if KVM is disabled

[Igor Mammedov <imammedo@redhat.com>]

On Wed,  9 Jan 2013 16:53:42 -0200
Eduardo Habkost <ehabkost@redhat.com> wrote:

> This is a cleanup that tries to solve two small issues:
> 
>  - We don't need a separate kvm_pv_eoi_features variable just to keep a
>    constant calculated at compile-time, and this style would require
>    adding a separate variable (that's declared twice because of the
>    CONFIG_KVM ifdef) for each feature that's going to be enabled/disable
>    by machine-type compat code.
>  - The pc-1.3 code is setting the kvm_pv_eoi flag on cpuid_kvm_features
>    even when KVM is disabled at runtime. This small incosistency in
>    the cpuid_kvm_features field isn't a problem today because
>    cpuid_kvm_features is ignored by the TCG code, but it may cause
>    unexpected problems later when refactoring the CPUID handling code.
> 
> This patch eliminates the kvm_pv_eoi_features variable and simply uses
> kvm_enabled() inside the enable_kvm_pv_eoi() compat function, so it
> enables kvm_pv_eoi only if KVM is enabled. I believe this makes the
> behavior of enable_kvm_pv_eoi() clearer and easier to understand.
> 
> Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>
> ---
> Cc: kvm@vger.kernel.org
> Cc: Michael S. Tsirkin <mst@redhat.com>
> Cc: Gleb Natapov <gleb@redhat.com>
> Cc: Marcelo Tosatti <mtosatti@redhat.com>
> 
[snip]
>  void host_cpuid(uint32_t function, uint32_t count,
> @@ -1343,13 +1337,15 @@ static int cpu_x86_parse_featurestr(x86_def_t *x86_cpu_def, char *features)
>      unsigned int i;
>      char *featurestr; /* Single 'key=value" string being parsed */
>      /* Features to be added */
> -    FeatureWordArray plus_features = {
> -        [FEAT_KVM] = kvm_default_features,
> -    };
> +    FeatureWordArray plus_features = { 0 };
>      /* Features to be removed */
>      FeatureWordArray minus_features = { 0 };
>      uint32_t numvalue;
>  
> +    if (kvm_enabled()) {
> +        plus_features[FEAT_KVM] = kvm_default_features;
> +    }
While touching it please move setting defaults to cpu_x86_register() or
cpu_x86_find_by_name() to so that cpu_x86_parse_featurestr() would deal only
with custom settings.

[snip]

-- 
Regards,
  Igor