KVM: host side for eoi optimization

Implementation of PV EOI using shared memory.
This reduces the number of exits an interrupt
causes as much as by half.

The idea is simple: there's a bit, per APIC, in guest memory,
that tells the guest that it does not need EOI.
We set it before injecting an interrupt and clear
before injecting a nested one. Guest tests it using
a test and clear operation - this is necessary
so that host can detect interrupt nesting -
and if set, it can skip the EOI MSR.

There's a new MSR to set the address of said register
in guest memory. Otherwise not much changed:
- Guest EOI is not required
- Register is tested & ISR is automatically cleared on exit

For testing results see description of previous patch
'kvm_para: guest side for eoi avoidance'.

Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Avi Kivity <avi@redhat.com>

1 files changed, 34 insertions, 0 deletions

diff --git a/arch/x86/kvm/trace.h b/arch/x86/kvm/trace.h
index 911d2641f14c..851914e207fc 100644
--- a/arch/x86/kvm/trace.h
+++ b/arch/x86/kvm/trace.h
@@ -517,6 +517,40 @@ TRACE_EVENT(kvm_apic_accept_irq,
                   __entry->coalesced ? " (coalesced)" : "")
 );
 
+TRACE_EVENT(kvm_eoi,
+            TP_PROTO(struct kvm_lapic *apic, int vector),
+            TP_ARGS(apic, vector),
+
+        TP_STRUCT__entry(
+                __field(        __u32,          apicid          )
+                __field(        int,            vector          )
+        ),
+
+        TP_fast_assign(
+                __entry->apicid         = apic->vcpu->vcpu_id;
+                __entry->vector         = vector;
+        ),
+
+        TP_printk("apicid %x vector %d", __entry->apicid, __entry->vector)
+);
+
+TRACE_EVENT(kvm_pv_eoi,
+            TP_PROTO(struct kvm_lapic *apic, int vector),
+            TP_ARGS(apic, vector),
+
+        TP_STRUCT__entry(
+                __field(        __u32,          apicid          )
+                __field(        int,            vector          )
+        ),
+
+        TP_fast_assign(
+                __entry->apicid         = apic->vcpu->vcpu_id;
+                __entry->vector         = vector;
+        ),
+
+        TP_printk("apicid %x vector %d", __entry->apicid, __entry->vector)
+);
+
 /*
  * Tracepoint for nested VMRUN
  */