kvm: add halt-polling cpu usage stats

Two new stats for exposing halt-polling cpu usage:
halt_poll_success_ns
halt_poll_fail_ns

Thus sum of these 2 stats is the total cpu time spent polling. "success"
means the VCPU polled until a virtual interrupt was delivered. "fail"
means the VCPU had to schedule out (either because the maximum poll time
was reached or it needed to yield the CPU).

To avoid touching every arch's kvm_vcpu_stat struct, only update and
export halt-polling cpu usage stats if we're on x86.

Exporting cpu usage as a u64 and in nanoseconds means we will overflow at
~500 years, which seems reasonably large.

Signed-off-by: David Matlack <dmatlack@google.com>
Signed-off-by: Jon Cargille <jcargill@google.com>
Reviewed-by: Jim Mattson <jmattson@google.com>

Message-Id: <20200508182240.68440-1-jcargill@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

10 files changed, 33 insertions, 3 deletions

diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
index 32c8a675e5a4..3833736dd064 100644
--- a/arch/arm64/include/asm/kvm_host.h
+++ b/arch/arm64/include/asm/kvm_host.h
@@ -415,6 +415,8 @@ struct kvm_vm_stat {
 struct kvm_vcpu_stat {
 	u64 halt_successful_poll;
 	u64 halt_attempted_poll;
+	u64 halt_poll_success_ns;
+	u64 halt_poll_fail_ns;
 	u64 halt_poll_invalid;
 	u64 halt_wakeup;
 	u64 hvc_exit_stat;
diff --git a/arch/arm64/kvm/guest.c b/arch/arm64/kvm/guest.c
index 863a0d158fb8..55ebb9ea74f6 100644
--- a/arch/arm64/kvm/guest.c
+++ b/arch/arm64/kvm/guest.c
@@ -40,6 +40,8 @@ struct kvm_stats_debugfs_item debugfs_entries[] = {
 	VCPU_STAT("mmio_exit_user", mmio_exit_user),
 	VCPU_STAT("mmio_exit_kernel", mmio_exit_kernel),
 	VCPU_STAT("exits", exits),
+	VCPU_STAT("halt_poll_success_ns", halt_poll_success_ns),
+	VCPU_STAT("halt_poll_fail_ns", halt_poll_fail_ns),
 	{ NULL }
 };
 
diff --git a/arch/mips/include/asm/kvm_host.h b/arch/mips/include/asm/kvm_host.h
index 2c343c346b79..e28b5a946e26 100644
--- a/arch/mips/include/asm/kvm_host.h
+++ b/arch/mips/include/asm/kvm_host.h
@@ -174,6 +174,8 @@ struct kvm_vcpu_stat {
 #endif
 	u64 halt_successful_poll;
 	u64 halt_attempted_poll;
+	u64 halt_poll_success_ns;
+	u64 halt_poll_fail_ns;
 	u64 halt_poll_invalid;
 	u64 halt_wakeup;
 };
diff --git a/arch/mips/kvm/mips.c b/arch/mips/kvm/mips.c
index 9787cdec33e6..99ed08aff31e 100644
--- a/arch/mips/kvm/mips.c
+++ b/arch/mips/kvm/mips.c
@@ -72,6 +72,8 @@ struct kvm_stats_debugfs_item debugfs_entries[] = {
 	VCPU_STAT("halt_attempted_poll", halt_attempted_poll),
 	VCPU_STAT("halt_poll_invalid", halt_poll_invalid),
 	VCPU_STAT("halt_wakeup", halt_wakeup),
+	VCPU_STAT("halt_poll_success_ns", halt_poll_success_ns),
+	VCPU_STAT("halt_poll_fail_ns", halt_poll_fail_ns),
 	{NULL}
 };
 
diff --git a/arch/powerpc/kvm/booke.c b/arch/powerpc/kvm/booke.c
index c2984cb6dfa7..888afe8d35cc 100644
--- a/arch/powerpc/kvm/booke.c
+++ b/arch/powerpc/kvm/booke.c
@@ -54,6 +54,8 @@ struct kvm_stats_debugfs_item debugfs_entries[] = {
 	VCPU_STAT("halt_wakeup", halt_wakeup),
 	VCPU_STAT("doorbell", dbell_exits),
 	VCPU_STAT("guest doorbell", gdbell_exits),
+	VCPU_STAT("halt_poll_success_ns", halt_poll_success_ns),
+	VCPU_STAT("halt_poll_fail_ns", halt_poll_fail_ns),
 	VM_STAT("remote_tlb_flush", remote_tlb_flush),
 	{ NULL }
 };
diff --git a/arch/s390/include/asm/kvm_host.h b/arch/s390/include/asm/kvm_host.h
index d6bcd34f3ec3..176f74cc2257 100644
--- a/arch/s390/include/asm/kvm_host.h
+++ b/arch/s390/include/asm/kvm_host.h
@@ -375,6 +375,8 @@ struct kvm_vcpu_stat {
 	u64 halt_poll_invalid;
 	u64 halt_no_poll_steal;
 	u64 halt_wakeup;
+	u64 halt_poll_success_ns;
+	u64 halt_poll_fail_ns;
 	u64 instruction_lctl;
 	u64 instruction_lctlg;
 	u64 instruction_stctl;
diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
index 389ff1b7cd43..a560a368f92c 100644
--- a/arch/s390/kvm/kvm-s390.c
+++ b/arch/s390/kvm/kvm-s390.c
@@ -75,6 +75,8 @@ struct kvm_stats_debugfs_item debugfs_entries[] = {
 	VCPU_STAT("halt_poll_invalid", halt_poll_invalid),
 	VCPU_STAT("halt_no_poll_steal", halt_no_poll_steal),
 	VCPU_STAT("halt_wakeup", halt_wakeup),
+	VCPU_STAT("halt_poll_success_ns", halt_poll_success_ns),
+	VCPU_STAT("halt_poll_fail_ns", halt_poll_fail_ns),
 	VCPU_STAT("instruction_lctlg", instruction_lctlg),
 	VCPU_STAT("instruction_lctl", instruction_lctl),
 	VCPU_STAT("instruction_stctl", instruction_stctl),
diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index a3ce391c9e7a..fd78bd44b2d6 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -1031,6 +1031,8 @@ struct kvm_vcpu_stat {
 	u64 irq_injections;
 	u64 nmi_injections;
 	u64 req_event;
+	u64 halt_poll_success_ns;
+	u64 halt_poll_fail_ns;
 };
 
 struct x86_instruction_info;
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 7fb7c1a8f1a5..471fccf7f850 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -217,6 +217,8 @@ struct kvm_stats_debugfs_item debugfs_entries[] = {
 	VCPU_STAT("nmi_injections", nmi_injections),
 	VCPU_STAT("req_event", req_event),
 	VCPU_STAT("l1d_flush", l1d_flush),
+	VCPU_STAT("halt_poll_success_ns", halt_poll_success_ns),
+	VCPU_STAT("halt_poll_fail_ns", halt_poll_fail_ns),
 	VM_STAT("mmu_shadow_zapped", mmu_shadow_zapped),
 	VM_STAT("mmu_pte_write", mmu_pte_write),
 	VM_STAT("mmu_pte_updated", mmu_pte_updated),
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 11844fad60fd..da6da386b591 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -2667,18 +2667,27 @@ out:
 	return ret;
 }
 
+static inline void
+update_halt_poll_stats(struct kvm_vcpu *vcpu, u64 poll_ns, bool waited)
+{
+	if (waited)
+		vcpu->stat.halt_poll_fail_ns += poll_ns;
+	else
+		vcpu->stat.halt_poll_success_ns += poll_ns;
+}
+
 /*
  * The vCPU has executed a HLT instruction with in-kernel mode enabled.
  */
 void kvm_vcpu_block(struct kvm_vcpu *vcpu)
 {
-	ktime_t start, cur;
+	ktime_t start, cur, poll_end;
 	bool waited = false;
 	u64 block_ns;
 
 	kvm_arch_vcpu_blocking(vcpu);
 
-	start = cur = ktime_get();
+	start = cur = poll_end = ktime_get();
 	if (vcpu->halt_poll_ns && !kvm_arch_no_poll(vcpu)) {
 		ktime_t stop = ktime_add_ns(ktime_get(), vcpu->halt_poll_ns);
 
@@ -2694,7 +2703,7 @@ void kvm_vcpu_block(struct kvm_vcpu *vcpu)
 					++vcpu->stat.halt_poll_invalid;
 				goto out;
 			}
-			cur = ktime_get();
+			poll_end = cur = ktime_get();
 		} while (single_task_running() && ktime_before(cur, stop));
 	}
 
@@ -2714,6 +2723,9 @@ out:
 	kvm_arch_vcpu_unblocking(vcpu);
 	block_ns = ktime_to_ns(cur) - ktime_to_ns(start);
 
+	update_halt_poll_stats(
+		vcpu, ktime_to_ns(ktime_sub(poll_end, start)), waited);
+
 	if (!kvm_arch_no_poll(vcpu)) {
 		if (!vcpu_valid_wakeup(vcpu)) {
 			shrink_halt_poll_ns(vcpu);