Re: [Qemu-devel] [PATCH 2/2] target-i386: kvm: enable all supported KVM features for -cpu host

[Igor Mammedov <imammedo@redhat.com>]

On Fri, 28 Dec 2012 16:37:34 -0200
Eduardo Habkost <ehabkost@redhat.com> wrote:

> When using -cpu host, we don't need to use the kvm_default_features
> variable, as the user is explicitly asking QEMU to enable all feature
> supported by the host.
> 
> This changes the kvm_cpu_fill_host() code to use GET_SUPPORTED_CPUID to
> initialize the kvm_features field, so we get all host KVM features
> enabled.

1_2 and 1_3 compat machines diff on pv_eoi flag, with this patch 1_2 might
have it set.
Is it ok from compat machines pov?

> 
> This will also allow use to properly check/enforce KVM features inside
> kvm_check_features_against_host() later. For example, we will be able to
> make this:
> 
>   $ qemu-system-x86_64 -cpu ...,+kvm_pv_eoi,enforce
> 
> refuse to start if kvm_pv_eoi is not supported by the host (after we fix
> kvm_check_features_against_host() to check KVM flags as well).
It would be nice to have kvm_check_features_against_host() patch in this
series to verify that this patch and previous patch works as expected.

> 
> Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>
> ---
>  target-i386/cpu.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/target-i386/cpu.c b/target-i386/cpu.c
> index 6e2d32d..76f19f0 100644
> --- a/target-i386/cpu.c
> +++ b/target-i386/cpu.c
> @@ -900,6 +900,8 @@ static void kvm_cpu_fill_host(x86_def_t *x86_cpu_def)
>      /* Other KVM-specific feature fields: */
>      x86_cpu_def->svm_features =
>                  kvm_arch_get_supported_cpuid(s, 0x8000000A, 0, R_EDX);
> +    x86_cpu_def->kvm_features =
> +                kvm_arch_get_supported_cpuid(s, KVM_CPUID_FEATURES, 0,
> R_EAX); 
>  #endif /* CONFIG_KVM */
>  }