Re: [Qemu-devel] [PATCH 04/19] cpu: call cpu_synchronize_post_init() from CPUClass.realize() if hotplugged

[Igor Mammedov <imammedo@redhat.com>]

On Thu, 11 Apr 2013 15:33:01 -0300
Eduardo Habkost <ehabkost@redhat.com> wrote:

> On Thu, Apr 11, 2013 at 04:51:43PM +0200, Igor Mammedov wrote:
> > ... to synchronize CPU state to KVM
> > 
> > Signed-off-by: Igor Mammedov <imammedo@redhat.com>
> > ---
> > v2:
> >   * linking kvm-stub.o to *-user target moved in separate patch
> > ---
> >  include/sysemu/kvm.h | 18 ++++++++++--------
> >  kvm-all.c            |  1 +
> >  kvm-stub.c           |  1 +
> >  qom/cpu.c            |  4 ++++
> >  vl.c                 |  1 -
> >  5 files changed, 16 insertions(+), 9 deletions(-)
> > 
> > diff --git a/include/sysemu/kvm.h b/include/sysemu/kvm.h
> > index 93cef28..8fb2489 100644
> > --- a/include/sysemu/kvm.h
> > +++ b/include/sysemu/kvm.h
> > @@ -250,8 +250,6 @@ int kvm_check_extension(KVMState *s, unsigned int extension);
> >  uint32_t kvm_arch_get_supported_cpuid(KVMState *env, uint32_t function,
> >                                        uint32_t index, int reg);
> >  void kvm_cpu_synchronize_state(CPUArchState *env);
> > -void kvm_cpu_synchronize_post_reset(CPUState *cpu);
> > -void kvm_cpu_synchronize_post_init(CPUState *cpu);
> >  
> >  /* generic hooks - to be moved/refactored once there are more users */
> >  
> > @@ -262,6 +260,16 @@ static inline void cpu_synchronize_state(CPUArchState *env)
> >      }
> >  }
> >  
> > +#if !defined(CONFIG_USER_ONLY)
> > +int kvm_physical_memory_addr_from_host(KVMState *s, void *ram_addr,
> > +                                       hwaddr *phys_addr);
> > +#endif
> > +
> > +#endif /* NEED_CPU_H */
> > +
> > +void kvm_cpu_synchronize_post_reset(CPUState *cpu);
> > +void kvm_cpu_synchronize_post_init(CPUState *cpu);
> > +
> >  static inline void cpu_synchronize_post_reset(CPUState *cpu)
> >  {
> >      if (kvm_enabled()) {
> > @@ -277,12 +285,6 @@ static inline void cpu_synchronize_post_init(CPUState *cpu)
> >  }
> >  
> >  
> > -#if !defined(CONFIG_USER_ONLY)
> > -int kvm_physical_memory_addr_from_host(KVMState *s, void *ram_addr,
> > -                                       hwaddr *phys_addr);
> > -#endif
> > -
> > -#endif
> >  int kvm_set_ioeventfd_mmio(int fd, uint32_t adr, uint32_t val, bool assign,
> >                             uint32_t size);
> >  
> > diff --git a/kvm-all.c b/kvm-all.c
> > index fc4e17c..1d17128 100644
> > --- a/kvm-all.c
> > +++ b/kvm-all.c
> > @@ -109,6 +109,7 @@ bool kvm_async_interrupts_allowed;
> >  bool kvm_irqfds_allowed;
> >  bool kvm_msi_via_irqfd_allowed;
> >  bool kvm_gsi_routing_allowed;
> > +bool kvm_allowed;
> >  
> >  static const KVMCapabilityInfo kvm_required_capabilites[] = {
> >      KVM_CAP_INFO(USER_MEMORY),
> > diff --git a/kvm-stub.c b/kvm-stub.c
> > index b34064a..8cb81c4 100644
> > --- a/kvm-stub.c
> > +++ b/kvm-stub.c
> > @@ -23,6 +23,7 @@ bool kvm_async_interrupts_allowed;
> >  bool kvm_irqfds_allowed;
> >  bool kvm_msi_via_irqfd_allowed;
> >  bool kvm_gsi_routing_allowed;
> > +bool kvm_allowed;
> >  
> >  int kvm_init_vcpu(CPUState *cpu)
> >  {
> > diff --git a/qom/cpu.c b/qom/cpu.c
> > index e242dcb..0c76712 100644
> > --- a/qom/cpu.c
> > +++ b/qom/cpu.c
> > @@ -20,6 +20,7 @@
> >  
> >  #include "qom/cpu.h"
> >  #include "qemu-common.h"
> > +#include "sysemu/kvm.h"
> >  
> >  void cpu_reset_interrupt(CPUState *cpu, int mask)
> >  {
> > @@ -57,6 +58,9 @@ static ObjectClass *cpu_common_class_by_name(const char *cpu_model)
> >  
> >  static void cpu_common_realizefn(DeviceState *dev, Error **errp)
> >  {
> > +    if (dev->hotplugged) {
> > +        cpu_synchronize_post_init(CPU(dev));
> > +    }
> 
> For reference: non-hotplugged CPUs have cpu_synchronize_post_init()
> called from cpu_synchronize_all_post_init(), that is called from main(),
> just after the machine->init() call.
> 
> That said, have you considered changing the code so that's possible to
> call cpu_synchronize_post_init() for all CPUs, so we could kill the
> cpu_synchronize_all_post_init() call entirely?
> 
> Maybe the solution for this is to realize non-hotplugged CPUs later,
> instead of realizing them very early inside the machine init function.
> If doing is not possible or not enough, we could use VM state notifiers
> to watch for the right moment to call cpu_synchronize_post_init().

I have not considered it, since question is out of scope CPU hot-plug.
It might be feasible to do so later in separate patch and remove
"if (dev->hotplugged)" condition tough.

I think it will be more appropriate when machine will QOM-ified, then
to make machine.realize() work it had to be done, but now I don't see
any gain doing so (providing all the trouble it might cause).

> 
> >  }
> >  
> >  static void cpu_class_init(ObjectClass *klass, void *data)
> > diff --git a/vl.c b/vl.c
> > index d694a90..21952c3 100644
> > --- a/vl.c
> > +++ b/vl.c
> > @@ -267,7 +267,6 @@ static NotifierList machine_init_done_notifiers =
> >      NOTIFIER_LIST_INITIALIZER(machine_init_done_notifiers);
> >  
> >  static bool tcg_allowed = true;
> > -bool kvm_allowed;
> >  bool xen_allowed;
> >  uint32_t xen_domid;
> >  enum xen_mode xen_mode = XEN_EMULATE;
> > -- 
> > 1.8.2
> > 
> 
> -- 
> Eduardo


-- 
Regards,
  Igor