Re: [kvm-devel] Second KVM process hangs eating 80-100% CPU on host during startup

[Alex D. <ale...@ya...>]

--- On Sat, 4/19/08, Marcelo Tosatti <mto...@re...> wrote:

> From: Marcelo Tosatti <mto...@re...>
> Subject: Re: [kvm-devel] Second KVM process hangs eating 80-100% CPU on host during startup
> To: "Alex Davis" <ale...@ya...>
> Cc: av...@qu..., kvm...@li...
> Date: Saturday, April 19, 2008, 7:11 PM
> On Sat, Apr 19, 2008 at 03:47:31PM -0700, Alex Davis wrote:
> > --- On Fri, 4/18/08, Avi Kivity
> <av...@qu...> wrote:
> > 
> > > From: Avi Kivity <av...@qu...>
> > > Subject: Re: [kvm-devel] Second KVM process hangs
> eating 80-100% CPU on host during startup
> > [snip]
> > 
> > I tried booting the guest with 'lpj=10682525'
> to work around the 
> > calibrate_delay issue, but that gave me:
> > 
> > [    0.004100] ENABLING IO-APIC IRQs
> > [    0.004100] ..TIMER: vector=0x31 apic1=0 pin1=0
> apic2=-1 pin2=-1
> > [    0.004100] ..MP-BIOS bug: 8254 timer not connected
> to IO-APIC
> > [    0.004100] ...trying to set up timer (IRQ0)
> through the 8259A ... failed.
> > [    0.004100] ...trying to set up timer as Virtual
> Wire IRQ ... failed.
> > [    0.004100] ...trying to set up timer as ExtINT IRQ
> ... failed :(.
> > [    0.004100] Kernel panic - not syncing: IO-APIC +
> timer doesn't work! Boot
> > with apic=debug and send a report.Then try booting
> with the 'noapic' option.
> > 
> > Booting with 'apic=debug' gives these
> additional lines:
> > [    0.004100] Getting VERSION: 50014
> > [    0.004100] Getting VERSION: 50014
> > [    0.004100] Getting ID: 0
> > [    0.004100] Getting LVT0: 700
> > [    0.004100] Getting LVT1: 10000
> 
> Hi Alex,
> 
> Can you please try the following.
> 
> KVM: PIT: make last_injected_time per-guest
> 
> Otherwise multiple guests use the same variable and boom.
> 
> Also use kvm_vcpu_kick() to make sure that if a timer
> triggers on 
> a different CPU the event won't be missed.
> 
> Signed-off-by: Marcelo Tosatti <mto...@re...>
> 
> 
> diff --git a/arch/x86/kvm/i8254.c b/arch/x86/kvm/i8254.c
> index 2852dd1..5697ad2 100644
> --- a/arch/x86/kvm/i8254.c
> +++ b/arch/x86/kvm/i8254.c
> @@ -200,10 +200,8 @@ int __pit_timer_fn(struct
> kvm_kpit_state *ps)
>  
>  	atomic_inc(&pt->pending);
>  	smp_mb__after_atomic_inc();
> -	if (vcpu0 && waitqueue_active(&vcpu0->wq))
> {
> -		vcpu0->arch.mp_state = KVM_MP_STATE_RUNNABLE;
> -		wake_up_interruptible(&vcpu0->wq);
> -	}
> +	if (vcpu0)
> +		kvm_vcpu_kick(vcpu0);
>  
>  	pt->timer.expires = ktime_add_ns(pt->timer.expires,
> pt->period);
>  	pt->scheduled = ktime_to_ns(pt->timer.expires);
> @@ -572,7 +570,6 @@ void kvm_inject_pit_timer_irqs(struct
> kvm_vcpu *vcpu)
>  	struct kvm_pit *pit = vcpu->kvm->arch.vpit;
>  	struct kvm *kvm = vcpu->kvm;
>  	struct kvm_kpit_state *ps;
> -	static unsigned long last_injected_time;
>  
>  	if (vcpu && pit) {
>  		ps = &pit->pit_state;
> @@ -582,11 +579,11 @@ void kvm_inject_pit_timer_irqs(struct
> kvm_vcpu *vcpu)
>  		 * 2. Last interrupt was accepted or waited for too long
> time*/
>  		if (atomic_read(&ps->pit_timer.pending)
> &&
>  		    (ps->inject_pending ||
> -		    (jiffies - last_injected_time
> +		    (jiffies - ps->last_injected_time
>  				>= KVM_MAX_PIT_INTR_INTERVAL))) {
>  			ps->inject_pending = 0;
>  			__inject_pit_timer_intr(kvm);
> -			last_injected_time = jiffies;
> +			ps->last_injected_time = jiffies;
>  		}
>  	}
>  }
> diff --git a/arch/x86/kvm/i8254.h b/arch/x86/kvm/i8254.h
> index e63ef38..db25c2a 100644
> --- a/arch/x86/kvm/i8254.h
> +++ b/arch/x86/kvm/i8254.h
> @@ -35,6 +35,7 @@ struct kvm_kpit_state {
>  	struct mutex lock;
>  	struct kvm_pit *pit;
>  	bool inject_pending; /* if inject pending interrupts */
> +	unsigned long last_injected_time;
>  };
>  
>  struct kvm_pit {


Problem(s) solved. Everything is working now. Can now boot both with and
without 'lpj='. The BogoMIPs are also being calculated correctly in secondary guests without 'lpj='. I'll play with it some more just to make sure, then I'll close the original bug.

Thanks, Marcelo et al.


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