KVM: Note down when cpu relax intercepted or pause loop exited

Noting pause loop exited vcpu or cpu relax intercepted helps in
filtering right candidate to yield. Wrong selection of vcpu;
i.e., a vcpu that just did a pl-exit or cpu relax intercepted may
contribute to performance degradation.

Signed-off-by: Raghavendra K T <raghavendra.kt@linux.vnet.ibm.com>
Reviewed-by: Marcelo Tosatti <mtosatti@redhat.com>
Reviewed-by: Rik van Riel <riel@redhat.com>
Tested-by: Christian Borntraeger <borntraeger@de.ibm.com> # on s390x
Signed-off-by: Avi Kivity <avi@redhat.com>

diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index db9aa91..361b36f 100644 (file)
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -183,6 +183,18 @@ struct kvm_vcpu {
        } async_pf;
 #endif
 
+#ifdef CONFIG_HAVE_KVM_CPU_RELAX_INTERCEPT
+       /*
+        * Cpu relax intercept or pause loop exit optimization
+        * in_spin_loop: set when a vcpu does a pause loop exit
+        *  or cpu relax intercepted.
+        * dy_eligible: indicates whether vcpu is eligible for directed yield.
+        */
+       struct {
+               bool in_spin_loop;
+               bool dy_eligible;
+       } spin_loop;
+#endif
        struct kvm_vcpu_arch arch;
 };
 
@@ -898,5 +910,27 @@ static inline bool kvm_check_request(int req, struct kvm_vcpu *vcpu)
        }
 }
 
+#ifdef CONFIG_HAVE_KVM_CPU_RELAX_INTERCEPT
+
+static inline void kvm_vcpu_set_in_spin_loop(struct kvm_vcpu *vcpu, bool val)
+{
+       vcpu->spin_loop.in_spin_loop = val;
+}
+static inline void kvm_vcpu_set_dy_eligible(struct kvm_vcpu *vcpu, bool val)
+{
+       vcpu->spin_loop.dy_eligible = val;
+}
+
+#else /* !CONFIG_HAVE_KVM_CPU_RELAX_INTERCEPT */
+
+static inline void kvm_vcpu_set_in_spin_loop(struct kvm_vcpu *vcpu, bool val)
+{
+}
+
+static inline void kvm_vcpu_set_dy_eligible(struct kvm_vcpu *vcpu, bool val)
+{
+}
+
+#endif /* CONFIG_HAVE_KVM_CPU_RELAX_INTERCEPT */
 #endif
 

diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 68dda51..0892b75 100644 (file)
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -239,6 +239,9 @@ int kvm_vcpu_init(struct kvm_vcpu *vcpu, struct kvm *kvm, unsigned id)
        }
        vcpu->run = page_address(page);
 
+       kvm_vcpu_set_in_spin_loop(vcpu, false);
+       kvm_vcpu_set_dy_eligible(vcpu, false);
+
        r = kvm_arch_vcpu_init(vcpu);
        if (r < 0)
                goto fail_free_run;
@@ -1585,6 +1588,7 @@ void kvm_vcpu_on_spin(struct kvm_vcpu *me)
        int pass;
        int i;
 
+       kvm_vcpu_set_in_spin_loop(me, true);
        /*
         * We boost the priority of a VCPU that is runnable but not
         * currently running, because it got preempted by something
@@ -1610,6 +1614,7 @@ void kvm_vcpu_on_spin(struct kvm_vcpu *me)
                        }
                }
        }
+       kvm_vcpu_set_in_spin_loop(me, false);
 }
 EXPORT_SYMBOL_GPL(kvm_vcpu_on_spin);