Re: [PATCH v1] KVM: s390: use switch vs jump table in interrupt.c

[Cornelia Huck <cohuck@redhat.com>]

On Wed, 7 Feb 2018 19:28:04 +0100
Christian Borntraeger <borntraeger@de.ibm.com> wrote:

> I see a minimal regression for uperf 1byte ping pong between two guests (~3%)
> Probably because the old code first handled IO interrupts and then did the remaing
> stuff.  Not sure if its worth to keep the old io_ioirq hack.

Hm, that confuses me a bit. We search the pending bit map, which should
give us the irq with the highest priority, and the switch/case still
starts out with I/O interrupts.

> 
> Other than that this looks good.
> 
> 
> On 02/06/2018 03:17 PM, David Hildenbrand wrote:
> > Just like for the interception handlers, let's also use a switch-case
> > in our interrupt delivery code.
> > 
> > Signed-off-by: David Hildenbrand <david@redhat.com>
> > ---
> >  arch/s390/kvm/interrupt.c | 84 ++++++++++++++++++++++++++++-------------------
> >  1 file changed, 50 insertions(+), 34 deletions(-)
> > 
> > diff --git a/arch/s390/kvm/interrupt.c b/arch/s390/kvm/interrupt.c
> > index aabf46f5f883..3ea9cfa31b16 100644
> > --- a/arch/s390/kvm/interrupt.c
> > +++ b/arch/s390/kvm/interrupt.c
> > @@ -187,12 +187,6 @@ static int cpu_timer_irq_pending(struct kvm_vcpu *vcpu)
> >  	return kvm_s390_get_cpu_timer(vcpu) >> 63;
> >  }
> > 
> > -static inline int is_ioirq(unsigned long irq_type)
> > -{
> > -	return ((irq_type >= IRQ_PEND_IO_ISC_7) &&
> > -		(irq_type <= IRQ_PEND_IO_ISC_0));
> > -}
> > -
> >  static uint64_t isc_to_isc_bits(int isc)
> >  {
> >  	return (0x80 >> isc) << 24;
> > @@ -1011,24 +1005,6 @@ static int __must_check __deliver_io(struct kvm_vcpu *vcpu,
> >  	return rc;
> >  }
> > 
> > -typedef int (*deliver_irq_t)(struct kvm_vcpu *vcpu);
> > -
> > -static const deliver_irq_t deliver_irq_funcs[] = {
> > -	[IRQ_PEND_MCHK_EX]        = __deliver_machine_check,
> > -	[IRQ_PEND_MCHK_REP]       = __deliver_machine_check,
> > -	[IRQ_PEND_PROG]           = __deliver_prog,
> > -	[IRQ_PEND_EXT_EMERGENCY]  = __deliver_emergency_signal,
> > -	[IRQ_PEND_EXT_EXTERNAL]   = __deliver_external_call,
> > -	[IRQ_PEND_EXT_CLOCK_COMP] = __deliver_ckc,
> > -	[IRQ_PEND_EXT_CPU_TIMER]  = __deliver_cpu_timer,
> > -	[IRQ_PEND_RESTART]        = __deliver_restart,
> > -	[IRQ_PEND_SET_PREFIX]     = __deliver_set_prefix,
> > -	[IRQ_PEND_PFAULT_INIT]    = __deliver_pfault_init,
> > -	[IRQ_PEND_EXT_SERVICE]    = __deliver_service,
> > -	[IRQ_PEND_PFAULT_DONE]    = __deliver_pfault_done,
> > -	[IRQ_PEND_VIRTIO]         = __deliver_virtio,
> > -};
> > -
> >  /* Check whether an external call is pending (deliverable or not) */
> >  int kvm_s390_ext_call_pending(struct kvm_vcpu *vcpu)
> >  {
> > @@ -1192,7 +1168,6 @@ void kvm_s390_clear_local_irqs(struct kvm_vcpu *vcpu)
> >  int __must_check kvm_s390_deliver_pending_interrupts(struct kvm_vcpu *vcpu)
> >  {
> >  	struct kvm_s390_local_interrupt *li = &vcpu->arch.local_int;
> > -	deliver_irq_t func;
> >  	int rc = 0;
> >  	unsigned long irq_type;
> >  	unsigned long irqs;
> > @@ -1212,16 +1187,57 @@ int __must_check kvm_s390_deliver_pending_interrupts(struct kvm_vcpu *vcpu)
> >  	while ((irqs = deliverable_irqs(vcpu)) && !rc) {
> >  		/* bits are in the reverse order of interrupt priority */
> >  		irq_type = find_last_bit(&irqs, IRQ_PEND_COUNT);
> > -		if (is_ioirq(irq_type)) {
> > +		switch (irq_type) {
> > +		case IRQ_PEND_IO_ISC_0:
> > +		case IRQ_PEND_IO_ISC_1:
> > +		case IRQ_PEND_IO_ISC_2:
> > +		case IRQ_PEND_IO_ISC_3:
> > +		case IRQ_PEND_IO_ISC_4:
> > +		case IRQ_PEND_IO_ISC_5:
> > +		case IRQ_PEND_IO_ISC_6:
> > +		case IRQ_PEND_IO_ISC_7:
> >  			rc = __deliver_io(vcpu, irq_type);
> > -		} else {
> > -			func = deliver_irq_funcs[irq_type];
> > -			if (!func) {
> > -				WARN_ON_ONCE(func == NULL);
> > -				clear_bit(irq_type, &li->pending_irqs);
> > -				continue;
> > -			}
> > -			rc = func(vcpu);
> > +			break;
> > +		case IRQ_PEND_MCHK_EX:
> > +		case IRQ_PEND_MCHK_REP:
> > +			rc = __deliver_machine_check(vcpu);
> > +			break;
> > +		case IRQ_PEND_PROG:
> > +			rc = __deliver_prog(vcpu);
> > +			break;
> > +		case IRQ_PEND_EXT_EMERGENCY:
> > +			rc = __deliver_emergency_signal(vcpu);
> > +			break;
> > +		case IRQ_PEND_EXT_EXTERNAL:
> > +			rc = __deliver_external_call(vcpu);
> > +			break;
> > +		case IRQ_PEND_EXT_CLOCK_COMP:
> > +			rc = __deliver_ckc(vcpu);
> > +			break;
> > +		case IRQ_PEND_EXT_CPU_TIMER:
> > +			rc = __deliver_cpu_timer(vcpu);
> > +			break;
> > +		case IRQ_PEND_RESTART:
> > +			rc = __deliver_restart(vcpu);
> > +			break;
> > +		case IRQ_PEND_SET_PREFIX:
> > +			rc = __deliver_set_prefix(vcpu);
> > +			break;
> > +		case IRQ_PEND_PFAULT_INIT:
> > +			rc = __deliver_pfault_init(vcpu);
> > +			break;
> > +		case IRQ_PEND_EXT_SERVICE:
> > +			rc = __deliver_service(vcpu);
> > +			break;
> > +		case IRQ_PEND_PFAULT_DONE:
> > +			rc = __deliver_pfault_done(vcpu);
> > +			break;
> > +		case IRQ_PEND_VIRTIO:
> > +			rc = __deliver_virtio(vcpu);
> > +			break;
> > +		default:
> > +			WARN_ONCE(1, "Unknown pending irq type %ld", irq_type);
> > +			clear_bit(irq_type, &li->pending_irqs);
> >  		}
> >  	}
> >   
>