Re: [Qemu-devel] [PATCH for-1.4 02/12] target-i386: Don't set any KVM flag by default if KVM is disabled

[Gleb Natapov <gleb@redhat.com>]

On Fri, Jan 18, 2013 at 11:58:34AM +0100, Andreas Färber wrote:
> Am 17.01.2013 21:59, schrieb Eduardo Habkost:
> > 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>
> 
> Fine with me if KVM folks agree.
> 
Acked-by: Gleb Natapov <gleb@redhat.com>

> Andreas
> 
> > ---
> > Cc: kvm@vger.kernel.org
> > Cc: Michael S. Tsirkin <mst@redhat.com>
> > Cc: Gleb Natapov <gleb@redhat.com>
> > Cc: Marcelo Tosatti <mtosatti@redhat.com>
> > 
> > Changes v2:
> >  - Coding style fix
> > 
> > Changes v3:
> >  - Eliminate #ifdef by using the fake KVM_FEATURE_PV_EOI #define
> > 
> > Changes v4:
> >  - Check kvm_enabled() when actually using kvm_default_features
> >  - Eliminate Yet Another #ifdef by using the fake KVM_FEATURE_*
> >    #defines on kvm_default_features initialization
> > 
> > Changes v5:
> >  - Rebase and move the kvm_enabled() check to cpu_x86_register()
> > ---
> >  target-i386/cpu.c | 12 ++++--------
> >  1 file changed, 4 insertions(+), 8 deletions(-)
> > 
> > diff --git a/target-i386/cpu.c b/target-i386/cpu.c
> > index 333745b..754eb6f 100644
> > --- a/target-i386/cpu.c
> > +++ b/target-i386/cpu.c
> > @@ -206,22 +206,16 @@ typedef struct model_features_t {
> >  int check_cpuid = 0;
> >  int enforce_cpuid = 0;
> >  
> > -#if defined(CONFIG_KVM)
> >  static uint32_t kvm_default_features = (1 << KVM_FEATURE_CLOCKSOURCE) |
> >          (1 << KVM_FEATURE_NOP_IO_DELAY) |
> >          (1 << KVM_FEATURE_CLOCKSOURCE2) |
> >          (1 << KVM_FEATURE_ASYNC_PF) |
> >          (1 << KVM_FEATURE_STEAL_TIME) |
> >          (1 << KVM_FEATURE_CLOCKSOURCE_STABLE_BIT);
> > -static const uint32_t kvm_pv_eoi_features = (0x1 << KVM_FEATURE_PV_EOI);
> > -#else
> > -static uint32_t kvm_default_features = 0;
> > -static const uint32_t kvm_pv_eoi_features = 0;
> > -#endif
> >  
> >  void enable_kvm_pv_eoi(void)
> >  {
> > -    kvm_default_features |= kvm_pv_eoi_features;
> > +    kvm_default_features |= (1UL << KVM_FEATURE_PV_EOI);
> >  }
> >  
> >  void host_cpuid(uint32_t function, uint32_t count,
> > @@ -1602,7 +1596,9 @@ int cpu_x86_register(X86CPU *cpu, const char *cpu_model)
> >          goto out;
> >      }
> >  
> > -    def->kvm_features |= kvm_default_features;
> > +    if (kvm_enabled()) {
> > +        def->kvm_features |= kvm_default_features;
> > +    }
> >      def->ext_features |= CPUID_EXT_HYPERVISOR;
> >  
> >      if (cpu_x86_parse_featurestr(def, features) < 0) {
> > 
> 
> 
> -- 
> SUSE LINUX Products GmbH, Maxfeldstr. 5, 90409 Nürnberg, Germany
> GF: Jeff Hawn, Jennifer Guild, Felix Imendörffer; HRB 16746 AG Nürnberg

--
			Gleb.