Re: [PATCH] fix "info cpus" halted state display

[Gleb Natapov <gleb@redhat.com>]

On Thu, May 13, 2010 at 03:57:05PM +0200, Jan Kiszka wrote:
> Gleb Natapov wrote:
> > When in-kernel irqchip is used env->halted is never used for anything
> > except "info cpus" command.
> 
> In fact, it's used in a few more places, namely cpu_dump_state and the
> gdbstub.
> 
Both of those places use env->halted the same way "info cpus" does:
print out cpu state. And the both call for cpu_synchronize_state()
before using env->halted.

> > Halted state is synced in
> > kvm_arch_save_mpstate() and showed by do_info_cpus() but otherwise never
> > looked at. Zeroing it here breaks "info cpus" since before
> > do_info_cpus() outputs env->halted in io thread it is zeroed here when
> > vcpu thread reenters kernel.
> 
> Looks good for current qemu-kvm.
> 
> Execution of kvm_cpu_exec once depended on env->halted, even for
> in-kernel irqchip, right?
Never in qemu-kvm AFAIR. May be at some point during merge between
upstream qemu and qemu-kvm such bug was introduced,

>                            Anyway, there are not such traces left here.
> We will just need to look at it again when pushing in-kernel irqchips
> upstream as its kvm loop looks different.
> 
> Jan
> 
> > 
> > Signed-off-by: Gleb Natapov <gleb@redhat.com>
> > diff --git a/qemu-kvm-x86.c b/qemu-kvm-x86.c
> > index 61d9331..0ec2881 100644
> > --- a/qemu-kvm-x86.c
> > +++ b/qemu-kvm-x86.c
> > @@ -922,10 +922,6 @@ void kvm_arch_load_regs(CPUState *env, int level)
> >          if (env->kvm_vcpu_update_vapic)
> >              kvm_tpr_enable_vapic(env);
> >      }
> > -    if (kvm_irqchip_in_kernel()) {
> > -        /* Avoid deadlock: no user space IRQ will ever clear it. */
> > -        env->halted = 0;
> > -    }
> >  
> >      kvm_put_vcpu_events(env, level);
> >      kvm_put_debugregs(env);
> > --
> > 			Gleb.
> 
> 



--
			Gleb.