/*
* kvm trace
*
* It is designed to allow debugging traces of kvm to be generated
* on UP / SMP machines. Each trace entry can be timestamped so that
* it's possible to reconstruct a chronological record of trace events.
* The implementation refers to blktrace kernel support.
*
* Copyright (c) 2008 Intel Corporation
* Copyright (C) 2006 Jens Axboe <axboe@kernel.dk>
*
* Authors: Feng(Eric) Liu, eric.e.liu@intel.com
*
* Date: Feb 2008
*/
#include <linux/module.h>
#include <linux/relay.h>
#include <linux/debugfs.h>
#include <linux/ktime.h>
#include <linux/kvm_host.h>
#define KVM_TRACE_STATE_RUNNING (1 << 0)
#define KVM_TRACE_STATE_PAUSE (1 << 1)
#define KVM_TRACE_STATE_CLEARUP (1 << 2)
struct kvm_trace {
int trace_state;
struct rchan *rchan;
struct dentry *lost_file;
atomic_t lost_records;
};
static struct kvm_trace *kvm_trace;
struct kvm_trace_probe {
const char *name;
const char *format;
u32 timestamp_in;
marker_probe_func *probe_func;
};
static inline int calc_rec_size(int timestamp, int extra)
{
int rec_size = KVM_TRC_HEAD_SIZE;
rec_size += extra;
return timestamp ? rec_size += KVM_TRC_CYCLE_SIZE : rec_size;
}
static void kvm_add_trace(void *probe_private, void *call_data,
const char *format, va_list *args)
{
struct kvm_trace_probe *p = probe_private;
struct kvm_trace *kt = kvm_trace;
struct kvm_trace_rec rec;
struct kvm_vcpu *vcpu;
int i, size;
u32 extra;
if (unlikely(kt->trace_state != KVM_TRACE_STATE_RUNNING))
return;
rec.rec_val = TRACE_REC_EVENT_ID(va_arg(*args, u32));
vcpu = va_arg(*args, struct kvm_vcpu *);
rec.pid = current->tgid;
rec.vcpu_id = vcpu->vcpu_id;
extra = va_arg(*args, u32);
WARN_ON(!(extra <= KVM_TRC_EXTRA_MAX));
extra = min_t(u32, extra, KVM_TRC_EXTRA_MAX);
rec.rec_val |= TRACE_REC_TCS(p->timestamp_in)
| TRACE_REC_NUM_DATA_ARGS(extra);
if (p->timestamp_in) {
rec.u.timestamp.timestamp = ktime_to_ns(ktime_get());
for (i = 0; i < extra; i++)
rec.u.timestamp.extra_u32[i] = va_arg(*args, u32);
} else {
for (i = 0; i < extra; i++)
rec.u.notimestamp.extra_u32[i] = va_arg(*args, u32);
}
size = calc_rec_size(p->timestamp_in, extra * sizeof(u32));
relay_write(kt->rchan, &rec, size);
}
static struct kvm_trace_probe kvm_trace_probes[] = {
{ "kvm_trace_entryexit", "%u %p %u %u %u %u %u %u", 1, kvm_add_trace },
{ "kvm_trace_handler", "%u %p %u %u %u %u %u %u", 0, kvm_add_trace },
};
static int lost_records_get(void *data, u64 *val)
{
struct kvm_trace *kt = data;
*val = atomic_read(&kt->lost_records);
return 0;
}
DEFINE_SIMPLE_ATTRIBUTE(kvm_trace_lost_ops, lost_records_get, NULL, "%llu\n");
/*
* The relay channel is used in "no-overwrite" mode, it keeps trace of how
* many times we encountered a full subbuffer, to tell user space app the
* lost records there were.
*/
static int kvm_subbuf_start_callback(struct rchan_buf *buf, void *subbuf,
void *prev_subbuf, size_t prev_padding)
{
struct kvm_trace *kt;
if (!relay_buf_full(buf)) {
if (!prev_subbuf) {
/*
* executed only once when the channel is opened
* save metadata as first record
*/
subbuf_start_reserve(buf, sizeof(u32));
*(u32 *)subbuf = 0x12345678;
}
return 1;
}
kt = buf->chan->private_data;
atomic_inc(&kt->lost_records);
return 0;
}
static struct dentry *kvm_create_buf_file_callack(const char *filename,
struct dentry *parent,
int mode,
struct rchan_buf *buf,
int *is_global)
{
return debugfs_create_file(filename, mode, parent, buf,
&relay_file_operations);
}
static int kvm_remove_buf_file_callback(struct dentry *dentry)
{
debugfs_remove(dentry);
return 0;
}
static struct rchan_callbacks kvm_relay_callbacks = {
.subbuf_start = kvm_subbuf_start_callback,
.create_buf_file = kvm_create_buf_file_callack,
.remove_buf_file = kvm_remove_buf_file_callback,
};
static int do_kvm_trace_enable(struct kvm_user_trace_setup *kuts)
{
struct kvm_trace *kt;
int i, r = -ENOMEM;
if (!kuts->buf_size || !kuts->buf_nr)
return -EINVAL;
kt = kzalloc(sizeof(*kt), GFP_KERNEL);
if (!kt)
goto err;
r = -EIO;
atomic_set(&kt->lost_records, 0);
kt->lost_file = debugfs_create_file("lost_records", 0444, kvm_debugfs_dir,
kt, &kvm_trace_lost_ops);
if (!kt->lost_file)
goto err;
kt->rchan = relay_open("trace", kvm_debugfs_dir, kuts->buf_size,
kuts->buf_nr, &kvm_relay_callbacks, kt);
if (!kt->rchan)
goto err;
kvm_trace = kt;
for (i = 0; i < ARRAY_SIZE(kvm_trace_probes); i++) {
struct kvm_trace_probe *p = &kvm_trace_probes[i];
r = marker_probe_register(p->name, p->format, p->probe_func, p);
if (r)
printk(KERN_INFO "Unable to register probe %s\n",
p->name);
}
kvm_trace->trace_state = KVM_TRACE_STATE_RUNNING;
return 0;
err:
if (kt) {
if (kt->lost_file)
debugfs_remove(kt->lost_file);
if (kt->rchan)
relay_close(kt->rchan);
kfree(kt);
}
return r;
}
static int kvm_trace_enable(char __user *arg)
{
struct kvm_user_trace_setup kuts;
int ret;
ret = copy_from_user(&kuts, arg, sizeof(kuts));
if (ret)
return -EFAULT;
ret = do_kvm_trace_enable(&kuts);
if (ret)
return ret;
return 0;
}
static int kvm_trace_pause(void)
{
struct kvm_trace *kt = kvm_trace;
int r = -EINVAL;
if (kt == NULL)
return r;
if (kt->trace_state == KVM_TRACE_STATE_RUNNING) {
kt->trace_state = KVM_TRACE_STATE_PAUSE;
relay_flush(kt->rchan);
r = 0;
}
return r;
}
void kvm_trace_cleanup(void)
{
struct kvm_trace *kt = kvm_trace;
int i;
if (kt == NULL)
return;
if (kt->trace_state == KVM_TRACE_STATE_RUNNING ||
kt->trace_state == KVM_TRACE_STATE_PAUSE) {
kt->trace_state = KVM_TRACE_STATE_CLEARUP;
for (i = 0; i < ARRAY_SIZE(kvm_trace_probes); i++) {
struct kvm_trace_probe *p = &kvm_trace_probes[i];
marker_probe_unregister(p->name, p->probe_func, p);
}
marker_synchronize_unregister();
relay_close(kt->rchan);
debugfs_remove(kt->lost_file);
kfree(kt);
}
}
int kvm_trace_ioctl(unsigned int ioctl, unsigned long arg)
{
void __user *argp = (void __user *)arg;
long r = -EINVAL;
if (!capable(CAP_SYS_ADMIN))
return -EPERM;
switch (ioctl) {
case KVM_TRACE_ENABLE:
r = kvm_trace_enable(argp);
break;
case KVM_TRACE_PAUSE:
r = kvm_trace_pause();
break;
case KVM_TRACE_DISABLE:
r = 0;
kvm_trace_cleanup();
break;
}
return r;
}
