On Tue, 13 Feb 2018 12:28:57 +0000 Christian Borntraeger <borntraeger@xxxxxxxxxx> wrote: > For interrupt injection of floating interrupts we queue the interrupt > either in the GISA or in the floating interrupt list. The first CPU > that looks at these data structures - either in KVM code or hardware > will then deliver that interrupt. To minimize latency we also: > -a: choose a VCPU to deliver that interrupt. We prefer idle CPUs > -b: we wake up the host thread that runs the VCPU > -c: set an I/O intervention bit for that CPU so that it exits guest > context as soon as the PSW I/O mask is enabled > This will make sure that this CPU will execute the interrupt delivery > code of KVM very soon. > > We can now optimize the injection case if we have exitless interrupts. > The wakeup is still necessary in case the target CPU sleeps. We can > avoid the I/O intervention request bit though. Whenever this > intervention request would be handled, the hardware could also directly > inject the interrupt on that CPU, no need to go through the interrupt > injection loop of KVM. > > Cc: Michael Mueller <mimu@xxxxxxxxxxxxxxxxxx> > Reviewed-by: Halil Pasic <pasic@xxxxxxxxxxxxxxxxxx> > Signed-off-by: Christian Borntraeger <borntraeger@xxxxxxxxxx> > --- > arch/s390/kvm/interrupt.c | 3 ++- > 1 file changed, 2 insertions(+), 1 deletion(-) > > diff --git a/arch/s390/kvm/interrupt.c b/arch/s390/kvm/interrupt.c > index aabf46f5f883..337a69bc04db 100644 > --- a/arch/s390/kvm/interrupt.c > +++ b/arch/s390/kvm/interrupt.c > @@ -1701,7 +1701,8 @@ static void __floating_irq_kick(struct kvm *kvm, u64 type) > kvm_s390_set_cpuflags(dst_vcpu, CPUSTAT_STOP_INT); > break; > case KVM_S390_INT_IO_MIN...KVM_S390_INT_IO_MAX: > - kvm_s390_set_cpuflags(dst_vcpu, CPUSTAT_IO_INT); > + if (!(type & KVM_S390_INT_IO_AI_MASK && kvm->arch.gisa)) > + kvm_s390_set_cpuflags(dst_vcpu, CPUSTAT_IO_INT); > break; > default: > kvm_s390_set_cpuflags(dst_vcpu, CPUSTAT_EXT_INT); Reviewed-by: Cornelia Huck <cohuck@xxxxxxxxxx> -- To unsubscribe from this list: send the line "unsubscribe linux-s390" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
