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Subject[PATCH 09/31] KVM: Add kvm trace userspace interface
Date
From: Feng(Eric) Liu <eric.e.liu@intel.com>

This interface allows user a space application to read the trace of kvm
related events through relayfs.

Signed-off-by: Feng (Eric) Liu <eric.e.liu@intel.com>
Signed-off-by: Avi Kivity <avi@qumranet.com>
---
arch/x86/kvm/Kconfig | 11 ++
arch/x86/kvm/Makefile | 3 +
include/linux/kvm_host.h | 14 +++
virt/kvm/kvm_main.c | 8 +-
virt/kvm/kvm_trace.c | 276 ++++++++++++++++++++++++++++++++++++++++++++++
5 files changed, 311 insertions(+), 1 deletions(-)
create mode 100644 virt/kvm/kvm_trace.c
diff --git a/arch/x86/kvm/Kconfig b/arch/x86/kvm/Kconfig
index 76c70ab..8d45fab 100644
--- a/arch/x86/kvm/Kconfig
+++ b/arch/x86/kvm/Kconfig
@@ -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
diff --git a/arch/x86/kvm/Makefile b/arch/x86/kvm/Makefile
index 4d0c22e..c97d35c 100644
--- a/arch/x86/kvm/Makefile
+++ b/arch/x86/kvm/Makefile
@@ -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

diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index 578c363..bd0c2d2 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -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
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 6a52c08..d5911d9 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -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);
diff --git a/virt/kvm/kvm_trace.c b/virt/kvm/kvm_trace.c
new file mode 100644
index 0000000..5425440
--- /dev/null
+++ b/virt/kvm/kvm_trace.c
@@ -0,0 +1,276 @@
+/*
+ * 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;
+}
--
1.5.5


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