Re: [Qemu-devel] [PATCH 03/10] target-i386: cpu: move xcc->kvm_required check to realize time

[Eduardo Habkost]

On Fri, Jun 10, 2016 at 09:15:44AM +0200, Igor Mammedov wrote:
> On Thu, 9 Jun 2016 15:34:30 -0300
> Eduardo Habkost <address@hidden> wrote:
> 
> > On Mon, Jun 06, 2016 at 05:16:45PM +0200, Igor Mammedov wrote:
> > > it will allow to drop custom cpu_x86_init() and use
> > > cpu_generic_init() insteadi, reducing cpu_x86_create()
> > > to a simple 3-liner.
> > > 
> > > Signed-off-by: Igor Mammedov <address@hidden>
> > > Eduardo Habkost <address@hidden>  
> > 
> > This triggers an assert when trying to use -cpu host with TCG:
> > 
> >   # ./x86_64-softmmu/qemu-system-x86_64 -machine accel=tcg -cpu host 
> > -nographic
> >   qemu-system-x86_64: /root/qemu/target-i386/cpu.c:1558: 
> > host_x86_cpu_initfn: Assertion `(kvm_allowed)' failed.
> >   Aborted
> This is not related to this patch and it was there before.

It is caused by this patch. The assert() was there, but you
removed the check on cpu_x86_create() that prevented it from
being triggered.

> 
> Maybe a separate patch saying that it replaces assert() in
> host_x86_cpu_initfn() with error check and user friendly
> error message at later stage.

We could apply the fix below as a separate patch before 03/10, or
just squash the fix in it. What do you think? (We can't do it as
a follow-up patch.)

If you prefer to suggest another fix, I will remove the series
from x86-next and wait for v3.

> 
> > 
> > I will squash the following fix in it:
> > 
> > diff --git a/target-i386/cpu.c b/target-i386/cpu.c
> > index 3f886a5..dcbfa0b 100644
> > --- a/target-i386/cpu.c
> > +++ b/target-i386/cpu.c
> > @@ -1555,16 +1555,17 @@ static void host_x86_cpu_initfn(Object *obj)
> >      CPUX86State *env = &cpu->env;
> >      KVMState *s = kvm_state;
> >  
> > -    assert(kvm_enabled());
> > -
> >      /* We can't fill the features array here because we don't know yet if
> >       * "migratable" is true or false.
> >       */
> >      cpu->host_features = true;
> >  
> > -    env->cpuid_level = kvm_arch_get_supported_cpuid(s, 0x0, 0, R_EAX);
> > -    env->cpuid_xlevel = kvm_arch_get_supported_cpuid(s, 0x80000000, 0, 
> > R_EAX);
> > -    env->cpuid_xlevel2 = kvm_arch_get_supported_cpuid(s, 0xC0000000, 0, 
> > R_EAX);
> > +    /* If KVM is disabled, x86_cpu_realizefn() will report an error later 
> > */
> > +    if (kvm_enabled()) {
> > +        env->cpuid_level = kvm_arch_get_supported_cpuid(s, 0x0, 0, R_EAX);
> > +        env->cpuid_xlevel = kvm_arch_get_supported_cpuid(s, 0x80000000, 0, 
> > R_EAX);
> > +        env->cpuid_xlevel2 = kvm_arch_get_supported_cpuid(s, 0xC0000000, 
> > 0, R_EAX);
> > +    }
> >  
> >      object_property_set_bool(OBJECT(cpu), true, "pmu", &error_abort);
> >  }
> > 
> 

-- 
Eduardo