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>
diff --git a/arch/powerpc/kvm/booke_interrupts.S b/arch/powerpc/kvm/booke_interrupts.S
index eb21868..084ebcd 100644
--- a/arch/powerpc/kvm/booke_interrupts.S
+++ b/arch/powerpc/kvm/booke_interrupts.S
@@ -107,6 +107,18 @@
li r6, 1
slw r6, r6, r5
+#ifdef CONFIG_KVM_EXIT_TIMING
+ /* save exit time */
+1:
+ mfspr r7, SPRN_TBRU
+ mfspr r8, SPRN_TBRL
+ mfspr r9, SPRN_TBRU
+ cmpw r9, r7
+ bne 1b
+ stw r8, VCPU_TIMING_EXIT_TBL(r4)
+ stw r9, VCPU_TIMING_EXIT_TBU(r4)
+#endif
+
/* Save the faulting instruction and all GPRs for emulation. */
andi. r7, r6, NEED_INST_MASK
beq ..skip_inst_copy
@@ -375,6 +387,18 @@
lwz r3, VCPU_SPRG7(r4)
mtspr SPRN_SPRG7, r3
+#ifdef CONFIG_KVM_EXIT_TIMING
+ /* save enter time */
+1:
+ mfspr r6, SPRN_TBRU
+ mfspr r7, SPRN_TBRL
+ mfspr r8, SPRN_TBRU
+ cmpw r8, r6
+ bne 1b
+ stw r7, VCPU_TIMING_LAST_ENTER_TBL(r4)
+ stw r8, VCPU_TIMING_LAST_ENTER_TBU(r4)
+#endif
+
/* Finish loading guest volatiles and jump to guest. */
lwz r3, VCPU_CTR(r4)
mtctr r3