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authorChristian Borntraeger <borntraeger@de.ibm.com>2018-01-29 12:22:45 +0100
committerChristian Borntraeger <borntraeger@de.ibm.com>2018-02-14 08:16:42 +0000
commita9810327726b01404ecde082c075a7468c433ddf (patch)
treedd8553dc823ea01e9d7b4803933c6e1febdc15ff
parent7928b2cbe55b2a410a0f5c1f154610059c57b1b2 (diff)
KVM: s390: optimize wakeup for exitless interrupts
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@linux.vnet.ibm.com> Reviewed-by: Halil Pasic <pasic@linux.vnet.ibm.com> Reviewed-by: David Hildenbrand <david@redhat.com> Reviewed-by: Cornelia Huck <cohuck@redhat.com> Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
-rw-r--r--arch/s390/kvm/interrupt.c3
1 files changed, 2 insertions, 1 deletions
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);