Re: [PATCH] call kvm_cpu_synchronize_state() on target vcpu

[Gleb Natapov <gleb@redhat.com>]

On Wed, Sep 09, 2009 at 05:47:13PM +0200, Jan Kiszka wrote:
> Gleb Natapov wrote:
> > regs_modified logic doesn't work if io thread calls
> > kvm_cpu_synchronize_state() since kvm_arch_get_registers()
> > returns only after vcpu thread is back to kernel. Setting
> > regs_modified to 1 at this stage causes loading of wrong vcpu
> > state on the next vcpu_run().
> 
> We need this upstream too, right? Could you file the corresponding patch?
> 
Upstream is single threaded. It shouldn't suffer from this bug.

> Thanks,
> Jan
> 
> > 
> > Signed-off-by: Gleb Natapov <gleb@redhat.com>
> > diff --git a/qemu-kvm.c b/qemu-kvm.c
> > index 06efd41..9ab0cec 100644
> > --- a/qemu-kvm.c
> > +++ b/qemu-kvm.c
> > @@ -874,14 +874,6 @@ int kvm_set_mpstate(kvm_vcpu_context_t vcpu, struct kvm_mp_state *mp_state)
> >  }
> >  #endif
> >  
> > -void kvm_cpu_synchronize_state(CPUState *env)
> > -{
> > -    if (!env->kvm_cpu_state.regs_modified) {
> > -        kvm_arch_get_registers(env);
> > -        env->kvm_cpu_state.regs_modified = 1;
> > -    }
> > -}
> > -
> >  static int handle_mmio(kvm_vcpu_context_t vcpu)
> >  {
> >      unsigned long addr = vcpu->run->mmio.phys_addr;
> > @@ -1539,6 +1531,22 @@ static void on_vcpu(CPUState *env, void (*func)(void *data), void *data)
> >          qemu_cond_wait(&qemu_work_cond);
> >  }
> >  
> > +static void do_kvm_cpu_synchronize_state(void *_env)
> > +{
> > +    CPUState *env = _env;
> > +    if (!env->kvm_cpu_state.regs_modified) {
> > +        kvm_arch_save_regs(env);
> > +        kvm_arch_load_mpstate(env);
> > +        env->kvm_cpu_state.regs_modified = 1;
> > +    }
> > +}
> > +
> > +void kvm_cpu_synchronize_state(CPUState *env)
> > +{
> > +    if (!env->kvm_cpu_state.regs_modified)
> > +        on_vcpu(env, do_kvm_cpu_synchronize_state, env);
> > +}
> > +
> >  static void inject_interrupt(void *data)
> >  {
> >      cpu_interrupt(current_env, (long) data);
> > diff --git a/qemu-kvm.h b/qemu-kvm.h
> > index 2c1730b..32f74b3 100644
> > --- a/qemu-kvm.h
> > +++ b/qemu-kvm.h
> > @@ -1153,12 +1153,6 @@ static inline int kvm_sync_vcpus(void)
> >      return 0;
> >  }
> >  
> > -static inline void kvm_arch_get_registers(CPUState *env)
> > -{
> > -    kvm_save_registers(env);
> > -    kvm_save_mpstate(env);
> > -}
> > -
> >  static inline void kvm_arch_put_registers(CPUState *env)
> >  {
> >      kvm_load_registers(env);
> > diff --git a/target-i386/helper.c b/target-i386/helper.c
> > index 4a16887..57c74a2 100644
> > --- a/target-i386/helper.c
> > +++ b/target-i386/helper.c
> > @@ -746,7 +746,7 @@ void cpu_dump_state(CPUState *env, FILE *f,
> >      static const char *seg_name[6] = { "ES", "CS", "SS", "DS", "FS", "GS" };
> >  
> >      if (kvm_enabled())
> > -        kvm_arch_get_registers(env);
> > +        kvm_cpu_synchronize_state(env);
> >  
> >      eflags = env->eflags;
> >  #ifdef TARGET_X86_64
> > --
> > 			Gleb.
> 
> -- 
> Siemens AG, Corporate Technology, CT SE 2
> Corporate Competence Center Embedded Linux

--
			Gleb.