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, 262 insertions, 0 deletions

diff --git a/arch/powerpc/kvm/timing.c b/arch/powerpc/kvm/timing.c
new file mode 100644
index 00000000000..f42d2728a6a
--- /dev/null
+++ b/arch/powerpc/kvm/timing.c
@@ -0,0 +1,262 @@
+/*
+ * 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. 2007
+ *
+ * Authors: Hollis Blanchard <hollisb@us.ibm.com>
+ *          Christian Ehrhardt <ehrhardt@linux.vnet.ibm.com>
+ */
+
+#include <linux/kvm_host.h>
+#include <linux/fs.h>
+#include <linux/seq_file.h>
+#include <linux/debugfs.h>
+#include <linux/uaccess.h>
+
+#include "timing.h"
+#include <asm/time.h>
+#include <asm-generic/div64.h>
+
+void kvmppc_init_timing_stats(struct kvm_vcpu *vcpu)
+{
+	int i;
+
+	/* pause guest execution to avoid concurrent updates */
+	local_irq_disable();
+	mutex_lock(&vcpu->mutex);
+
+	vcpu->arch.last_exit_type = 0xDEAD;
+	for (i = 0; i < __NUMBER_OF_KVM_EXIT_TYPES; i++) {
+		vcpu->arch.timing_count_type[i] = 0;
+		vcpu->arch.timing_max_duration[i] = 0;
+		vcpu->arch.timing_min_duration[i] = 0xFFFFFFFF;
+		vcpu->arch.timing_sum_duration[i] = 0;
+		vcpu->arch.timing_sum_quad_duration[i] = 0;
+	}
+	vcpu->arch.timing_last_exit = 0;
+	vcpu->arch.timing_exit.tv64 = 0;
+	vcpu->arch.timing_last_enter.tv64 = 0;
+
+	mutex_unlock(&vcpu->mutex);
+	local_irq_enable();
+}
+
+static void add_exit_timing(struct kvm_vcpu *vcpu,
+					u64 duration, int type)
+{
+	u64 old;
+
+	do_div(duration, tb_ticks_per_usec);
+	if (unlikely(duration > 0xFFFFFFFF)) {
+		printk(KERN_ERR"%s - duration too big -> overflow"
+			" duration %lld type %d exit #%d\n",
+			__func__, duration, type,
+			vcpu->arch.timing_count_type[type]);
+		return;
+	}
+
+	vcpu->arch.timing_count_type[type]++;
+
+	/* sum */
+	old = vcpu->arch.timing_sum_duration[type];
+	vcpu->arch.timing_sum_duration[type] += duration;
+	if (unlikely(old > vcpu->arch.timing_sum_duration[type])) {
+		printk(KERN_ERR"%s - wrap adding sum of durations"
+			" old %lld new %lld type %d exit # of type %d\n",
+			__func__, old, vcpu->arch.timing_sum_duration[type],
+			type, vcpu->arch.timing_count_type[type]);
+	}
+
+	/* square sum */
+	old = vcpu->arch.timing_sum_quad_duration[type];
+	vcpu->arch.timing_sum_quad_duration[type] += (duration*duration);
+	if (unlikely(old > vcpu->arch.timing_sum_quad_duration[type])) {
+		printk(KERN_ERR"%s - wrap adding sum of squared durations"
+			" old %lld new %lld type %d exit # of type %d\n",
+			__func__, old,
+			vcpu->arch.timing_sum_quad_duration[type],
+			type, vcpu->arch.timing_count_type[type]);
+	}
+
+	/* set min/max */
+	if (unlikely(duration < vcpu->arch.timing_min_duration[type]))
+		vcpu->arch.timing_min_duration[type] = duration;
+	if (unlikely(duration > vcpu->arch.timing_max_duration[type]))
+		vcpu->arch.timing_max_duration[type] = duration;
+}
+
+void kvmppc_update_timing_stats(struct kvm_vcpu *vcpu)
+{
+	u64 exit = vcpu->arch.timing_last_exit;
+	u64 enter = vcpu->arch.timing_last_enter.tv64;
+
+	/* save exit time, used next exit when the reenter time is known */
+	vcpu->arch.timing_last_exit = vcpu->arch.timing_exit.tv64;
+
+	if (unlikely(vcpu->arch.last_exit_type == 0xDEAD || exit == 0))
+		return; /* skip incomplete cycle (e.g. after reset) */
+
+	/* update statistics for average and standard deviation */
+	add_exit_timing(vcpu, (enter - exit), vcpu->arch.last_exit_type);
+	/* enter -> timing_last_exit is time spent in guest - log this too */
+	add_exit_timing(vcpu, (vcpu->arch.timing_last_exit - enter),
+			TIMEINGUEST);
+}
+
+static const char *kvm_exit_names[__NUMBER_OF_KVM_EXIT_TYPES] = {
+	[MMIO_EXITS] = 			"MMIO",
+	[DCR_EXITS] =			"DCR",
+	[SIGNAL_EXITS] =		"SIGNAL",
+	[ITLB_REAL_MISS_EXITS] =	"ITLBREAL",
+	[ITLB_VIRT_MISS_EXITS] =	"ITLBVIRT",
+	[DTLB_REAL_MISS_EXITS] =	"DTLBREAL",
+	[DTLB_VIRT_MISS_EXITS] =	"DTLBVIRT",
+	[SYSCALL_EXITS] =		"SYSCALL",
+	[ISI_EXITS] =			"ISI",
+	[DSI_EXITS] =			"DSI",
+	[EMULATED_INST_EXITS] =		"EMULINST",
+	[EMULATED_MTMSRWE_EXITS] =	"EMUL_WAIT",
+	[EMULATED_WRTEE_EXITS] =	"EMUL_WRTEE",
+	[EMULATED_MTSPR_EXITS] =	"EMUL_MTSPR",
+	[EMULATED_MFSPR_EXITS] =	"EMUL_MFSPR",
+	[EMULATED_MTMSR_EXITS] =	"EMUL_MTMSR",
+	[EMULATED_MFMSR_EXITS] =	"EMUL_MFMSR",
+	[EMULATED_TLBSX_EXITS] =	"EMUL_TLBSX",
+	[EMULATED_TLBWE_EXITS] =	"EMUL_TLBWE",
+	[EMULATED_RFI_EXITS] =		"EMUL_RFI",
+	[DEC_EXITS] =			"DEC",
+	[EXT_INTR_EXITS] =		"EXTINT",
+	[HALT_WAKEUP] =			"HALT",
+	[USR_PR_INST] =			"USR_PR_INST",
+	[FP_UNAVAIL] =			"FP_UNAVAIL",
+	[DEBUG_EXITS] =			"DEBUG",
+	[TIMEINGUEST] =			"TIMEINGUEST"
+};
+
+static int kvmppc_exit_timing_show(struct seq_file *m, void *private)
+{
+	struct kvm_vcpu *vcpu = m->private;
+	int i;
+	u64 min, max;
+
+	for (i = 0; i < __NUMBER_OF_KVM_EXIT_TYPES; i++) {
+		if (vcpu->arch.timing_min_duration[i] == 0xFFFFFFFF)
+			min = 0;
+		else
+			min = vcpu->arch.timing_min_duration[i];
+		if (vcpu->arch.timing_max_duration[i] == 0)
+			max = 0;
+		else
+			max = vcpu->arch.timing_max_duration[i];
+
+		seq_printf(m, "%12s: count %10d min %10lld "
+			"max %10lld sum %20lld sum_quad %20lld\n",
+			kvm_exit_names[i], vcpu->arch.timing_count_type[i],
+			vcpu->arch.timing_min_duration[i],
+			vcpu->arch.timing_max_duration[i],
+			vcpu->arch.timing_sum_duration[i],
+			vcpu->arch.timing_sum_quad_duration[i]);
+	}
+	return 0;
+}
+
+static ssize_t kvmppc_exit_timing_write(struct file *file,
+				       const char __user *user_buf,
+				       size_t count, loff_t *ppos)
+{
+	size_t len;
+	int err;
+	const char __user *p;
+	char c;
+
+	len = 0;
+	p = user_buf;
+	while (len < count) {
+		if (get_user(c, p++))
+			err = -EFAULT;
+		if (c == 0 || c == '\n')
+			break;
+		len++;
+	}
+
+	if (len > 1) {
+		err = -EINVAL;
+		goto done;
+	}
+
+	if (copy_from_user(&c, user_buf, sizeof(c))) {
+		err = -EFAULT;
+		goto done;
+	}
+
+	if (c == 'c') {
+		struct seq_file *seqf = (struct seq_file *)file->private_data;
+		struct kvm_vcpu *vcpu = seqf->private;
+		/* write does not affect out buffers previsously generated with
+		 * show. Seq file is locked here to prevent races of init with
+		 * a show call */
+		mutex_lock(&seqf->lock);
+		kvmppc_init_timing_stats(vcpu);
+		mutex_unlock(&seqf->lock);
+		err = count;
+	} else {
+		err = -EINVAL;
+		goto done;
+	}
+
+done:
+	return err;
+}
+
+static int kvmppc_exit_timing_open(struct inode *inode, struct file *file)
+{
+	return single_open(file, kvmppc_exit_timing_show, inode->i_private);
+}
+
+static struct file_operations kvmppc_exit_timing_fops = {
+	.owner   = THIS_MODULE,
+	.open    = kvmppc_exit_timing_open,
+	.read    = seq_read,
+	.write   = kvmppc_exit_timing_write,
+	.llseek  = seq_lseek,
+	.release = single_release,
+};
+
+void kvmppc_create_vcpu_debugfs(struct kvm_vcpu *vcpu, unsigned int id)
+{
+	static char dbg_fname[50];
+	struct dentry *debugfs_file;
+
+	snprintf(dbg_fname, sizeof(dbg_fname), "vm%u_vcpu%03u_timing",
+		 current->pid, id);
+	debugfs_file = debugfs_create_file(dbg_fname, 0666,
+					kvm_debugfs_dir, vcpu,
+					&kvmppc_exit_timing_fops);
+
+	if (!debugfs_file) {
+		printk(KERN_ERR"%s: error creating debugfs file %s\n",
+			__func__, dbg_fname);
+		return;
+	}
+
+	vcpu->arch.debugfs_exit_timing = debugfs_file;
+}
+
+void kvmppc_remove_vcpu_debugfs(struct kvm_vcpu *vcpu)
+{
+	if (vcpu->arch.debugfs_exit_timing) {
+		debugfs_remove(vcpu->arch.debugfs_exit_timing);
+		vcpu->arch.debugfs_exit_timing = NULL;
+	}
+}