Commit d4c9ff2d authored by Feng(Eric) Liu's avatar Feng(Eric) Liu Committed by Avi Kivity
Browse files

KVM: Add kvm trace userspace interface



This interface allows user a space application to read the trace of kvm
related events through relayfs.
Signed-off-by: default avatarFeng (Eric) Liu <eric.e.liu@intel.com>
Signed-off-by: default avatarAvi Kivity <avi@qumranet.com>
parent 048354c8
......@@ -50,6 +50,17 @@ config KVM_AMD
Provides support for KVM on AMD processors equipped with the AMD-V
(SVM) extensions.
config KVM_TRACE
bool "KVM trace support"
depends on KVM && MARKERS && SYSFS
select RELAY
select DEBUG_FS
default n
---help---
This option allows reading a trace of kvm-related events through
relayfs. Note the ABI is not considered stable and will be
modified in future updates.
# OK, it's a little counter-intuitive to do this, but it puts it neatly under
# the virtualization menu.
source drivers/lguest/Kconfig
......
......@@ -3,6 +3,9 @@
#
common-objs = $(addprefix ../../../virt/kvm/, kvm_main.o ioapic.o)
ifeq ($(CONFIG_KVM_TRACE),y)
common-objs += $(addprefix ../../../virt/kvm/, kvm_trace.o)
endif
EXTRA_CFLAGS += -Ivirt/kvm -Iarch/x86/kvm
......
......@@ -15,6 +15,7 @@
#include <linux/sched.h>
#include <linux/mm.h>
#include <linux/preempt.h>
#include <linux/marker.h>
#include <asm/signal.h>
#include <linux/kvm.h>
......@@ -309,5 +310,18 @@ struct kvm_stats_debugfs_item {
struct dentry *dentry;
};
extern struct kvm_stats_debugfs_item debugfs_entries[];
extern struct dentry *debugfs_dir;
#ifdef CONFIG_KVM_TRACE
int kvm_trace_ioctl(unsigned int ioctl, unsigned long arg);
void kvm_trace_cleanup(void);
#else
static inline
int kvm_trace_ioctl(unsigned int ioctl, unsigned long arg)
{
return -EINVAL;
}
#define kvm_trace_cleanup() ((void)0)
#endif
#endif
......@@ -60,7 +60,7 @@ EXPORT_SYMBOL_GPL(kvm_vcpu_cache);
static __read_mostly struct preempt_ops kvm_preempt_ops;
static struct dentry *debugfs_dir;
struct dentry *debugfs_dir;
static long kvm_vcpu_ioctl(struct file *file, unsigned int ioctl,
unsigned long arg);
......@@ -1191,6 +1191,11 @@ static long kvm_dev_ioctl(struct file *filp,
r += PAGE_SIZE; /* pio data page */
#endif
break;
case KVM_TRACE_ENABLE:
case KVM_TRACE_PAUSE:
case KVM_TRACE_DISABLE:
r = kvm_trace_ioctl(ioctl, arg);
break;
default:
return kvm_arch_dev_ioctl(filp, ioctl, arg);
}
......@@ -1519,6 +1524,7 @@ EXPORT_SYMBOL_GPL(kvm_init);
void kvm_exit(void)
{
kvm_trace_cleanup();
misc_deregister(&kvm_dev);
kmem_cache_destroy(kvm_vcpu_cache);
sysdev_unregister(&kvm_sysdev);
......
/*
* 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/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 cycle_in;
marker_probe_func *probe_func;
};
static inline int calc_rec_size(int cycle, int extra)
{
int rec_size = KVM_TRC_HEAD_SIZE;
rec_size += extra;
return cycle ? 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, extra, size;
if (unlikely(kt->trace_state != KVM_TRACE_STATE_RUNNING))
return;
rec.event = 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.extra_u32 = extra;
rec.cycle_in = p->cycle_in;
if (rec.cycle_in) {
u64 cycle = 0;
cycle = get_cycles();
rec.u.cycle.cycle_lo = (u32)cycle;
rec.u.cycle.cycle_hi = (u32)(cycle >> 32);
for (i = 0; i < rec.extra_u32; i++)
rec.u.cycle.extra_u32[i] = va_arg(*args, u32);
} else {
for (i = 0; i < rec.extra_u32; i++)
rec.u.nocycle.extra_u32[i] = va_arg(*args, u32);
}
size = calc_rec_size(rec.cycle_in, rec.extra_u32 * 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))
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, debugfs_dir,
kt, &kvm_trace_lost_ops);
if (!kt->lost_file)
goto err;
kt->rchan = relay_open("trace", 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);
}
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;
}
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