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

Christian Borntraeger
2018-02-07T18:28:04Z

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.

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);
> }
> }
>