[PATCH RFC V4 2/3] kvm: Note down when cpu relax intercepted or pause loop exited

[Raghavendra K T]

From: Raghavendra K T <raghavendra...@linux.vnet.ibm.com>

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...@linux.vnet.ibm.com>
---
V2 was:
Reviewed-by: Rik van Riel <r...@redhat.com>

 include/linux/kvm_host.h |   37 +++++++++++++++++++++++++++++++++++++
 virt/kvm/kvm_main.c      |    5 +++++
 2 files changed, 42 insertions(+), 0 deletions(-)

diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index c446435..fa353bd 100644
--- 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
+        * cpu_relax_intercepted: 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 cpu_relax_intercepted;
+               bool dy_eligible;
+       } ple;
+#endif
        struct kvm_vcpu_arch arch;
 };
 
@@ -890,5 +902,30 @@ 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_cpu_relax_intercepted(struct kvm_vcpu *vcpu,
+                                                       bool val)
+{
+       vcpu->ple.cpu_relax_intercepted = val;
+}
+static inline void kvm_vcpu_set_dy_eligible(struct kvm_vcpu *vcpu, bool val)
+{
+       vcpu->ple.dy_eligible = val;
+}
+
+#else /* !CONFIG_HAVE_KVM_CPU_RELAX_INTERCEPT */
+
+static inline void kvm_vcpu_set_cpu_relax_intercepted(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 7e14068..c50213f 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -236,6 +236,9 @@ int kvm_vcpu_init(struct kvm_vcpu *vcpu, struct kvm *kvm, 
unsigned id)
        }
        vcpu->run = page_address(page);
 
+       kvm_vcpu_set_cpu_relax_intercepted(vcpu, false);
+       kvm_vcpu_set_dy_eligible(vcpu, false);
+
        r = kvm_arch_vcpu_init(vcpu);
        if (r < 0)
                goto fail_free_run;
@@ -1577,6 +1580,7 @@ void kvm_vcpu_on_spin(struct kvm_vcpu *me)
        int pass;
        int i;
 
+       kvm_vcpu_set_cpu_relax_intercepted(me, true);
        /*
         * We boost the priority of a VCPU that is runnable but not
         * currently running, because it got preempted by something
@@ -1602,6 +1606,7 @@ void kvm_vcpu_on_spin(struct kvm_vcpu *me)
                        }
                }
        }
+       kvm_vcpu_set_cpu_relax_intercepted(me, false);
 }
 EXPORT_SYMBOL_GPL(kvm_vcpu_on_spin);
 

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