KVM: ppc: Implement in-kernel exit timing statistics

Existing KVM statistics are either just counters (kvm_stat) reported for
KVM generally or trace based aproaches like kvm_trace.
For KVM on powerpc we had the need to track the timings of the different exit
types. While this could be achieved parsing data created with a kvm_trace
extension this adds too much overhead (at least on embedded PowerPC) slowing
down the workloads we wanted to measure.

Therefore this patch adds a in-kernel exit timing statistic to the powerpc kvm
code. These statistic is available per vm&vcpu under the kvm debugfs directory.
As this statistic is low, but still some overhead it can be enabled via a
.config entry and should be off by default.

Since this patch touched all powerpc kvm_stat code anyway this code is now
merged and simplified together with the exit timing statistic code (still
working with exit timing disabled in .config).

Signed-off-by: Christian Ehrhardt <ehrhardt@linux.vnet.ibm.com>
Signed-off-by: Hollis Blanchard <hollisb@us.ibm.com>
Signed-off-by: Avi Kivity <avi@redhat.com>

1 files changed, 102 insertions, 0 deletions

diff --git a/arch/powerpc/kvm/timing.h b/arch/powerpc/kvm/timing.h
new file mode 100644
index 000000000000..1af7181fa2b5
--- /dev/null
+++ b/arch/powerpc/kvm/timing.h
@@ -0,0 +1,102 @@
+/*
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License, version 2, as
+ * published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
+ *
+ * Copyright IBM Corp. 2008
+ *
+ * Authors: Christian Ehrhardt <ehrhardt@linux.vnet.ibm.com>
+ */
+
+#ifndef __POWERPC_KVM_EXITTIMING_H__
+#define __POWERPC_KVM_EXITTIMING_H__
+
+#include <linux/kvm_host.h>
+#include <asm/kvm_host.h>
+
+#ifdef CONFIG_KVM_EXIT_TIMING
+void kvmppc_init_timing_stats(struct kvm_vcpu *vcpu);
+void kvmppc_update_timing_stats(struct kvm_vcpu *vcpu);
+void kvmppc_create_vcpu_debugfs(struct kvm_vcpu *vcpu, unsigned int id);
+void kvmppc_remove_vcpu_debugfs(struct kvm_vcpu *vcpu);
+
+static inline void kvmppc_set_exit_type(struct kvm_vcpu *vcpu, int type)
+{
+        vcpu->arch.last_exit_type = type;
+}
+
+#else
+/* if exit timing is not configured there is no need to build the c file */
+static inline void kvmppc_init_timing_stats(struct kvm_vcpu *vcpu) {}
+static inline void kvmppc_update_timing_stats(struct kvm_vcpu *vcpu) {}
+static inline void kvmppc_create_vcpu_debugfs(struct kvm_vcpu *vcpu,
+                                                unsigned int id) {}
+static inline void kvmppc_remove_vcpu_debugfs(struct kvm_vcpu *vcpu) {}
+static inline void kvmppc_set_exit_type(struct kvm_vcpu *vcpu, int type) {}
+#endif /* CONFIG_KVM_EXIT_TIMING */
+
+/* account the exit in kvm_stats */
+static inline void account_exit_stat(struct kvm_vcpu *vcpu, int type)
+{
+        /* type has to be known at build time for optimization */
+        BUILD_BUG_ON(__builtin_constant_p(type));
+        switch (type) {
+        case EXT_INTR_EXITS:
+                vcpu->stat.ext_intr_exits++;
+                break;
+        case DEC_EXITS:
+                vcpu->stat.dec_exits++;
+                break;
+        case EMULATED_INST_EXITS:
+                vcpu->stat.emulated_inst_exits++;
+                break;
+        case DCR_EXITS:
+                vcpu->stat.dcr_exits++;
+                break;
+        case DSI_EXITS:
+                vcpu->stat.dsi_exits++;
+                break;
+        case ISI_EXITS:
+                vcpu->stat.isi_exits++;
+                break;
+        case SYSCALL_EXITS:
+                vcpu->stat.syscall_exits++;
+                break;
+        case DTLB_REAL_MISS_EXITS:
+                vcpu->stat.dtlb_real_miss_exits++;
+                break;
+        case DTLB_VIRT_MISS_EXITS:
+                vcpu->stat.dtlb_virt_miss_exits++;
+                break;
+        case MMIO_EXITS:
+                vcpu->stat.mmio_exits++;
+                break;
+        case ITLB_REAL_MISS_EXITS:
+                vcpu->stat.itlb_real_miss_exits++;
+                break;
+        case ITLB_VIRT_MISS_EXITS:
+                vcpu->stat.itlb_virt_miss_exits++;
+                break;
+        case SIGNAL_EXITS:
+                vcpu->stat.signal_exits++;
+                break;
+        }
+}
+
+/* wrapper to set exit time and account for it in kvm_stats */
+static inline void account_exit(struct kvm_vcpu *vcpu, int type)
+{
+        kvmppc_set_exit_type(vcpu, type);
+        account_exit_stat(vcpu, type);
+}
+
+#endif /* __POWERPC_KVM_EXITTIMING_H__ */