[PATCH RFC 2/5] Create relay channels and add trace data

[PATCH RFC 2/5] Create relay channels and add trace data

[Liu, Eric E]

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>From 41d65b55580d3f07f9f1c50e89e3d64c5d10fbaf Mon Sep 17 00:00:00 2001
From: Feng (Eric) Liu <eric.e.liu@intel.com>
Date: Tue, 1 Apr 2008 07:26:14 -0400
Subject: [PATCH] KVM: Add kvm trace support. when config KVM_TRACE, it
allows userspace app to read the trace of kvm_related
events through the relayfs.

Signed-off-by: Feng (Eric) Liu <eric.e.liu@intel.com>
---
 arch/x86/kvm/Kconfig  |   10 ++
 arch/x86/kvm/Makefile |    3 +
 virt/kvm/kvm_trace.c  |  245
+++++++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 258 insertions(+), 0 deletions(-)
 create mode 100644 virt/kvm/kvm_trace.c

diff --git a/arch/x86/kvm/Kconfig b/arch/x86/kvm/Kconfig
index 76c70ab..d51ffb3 100644
--- a/arch/x86/kvm/Kconfig
+++ b/arch/x86/kvm/Kconfig
@@ -50,6 +50,16 @@ 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
+	  the relayfs. 
+
 # 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/virt/kvm/kvm_trace.c b/virt/kvm/kvm_trace.c
new file mode 100644
index 0000000..a07760d
--- /dev/null
+++ b/virt/kvm/kvm_trace.c
@@ -0,0 +1,245 @@
+/*
+ * 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.
+ *
+ * Copyright (c) 2008 Intel Corporation
+ *
+ * Authors: 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_CLEARUP 	(1 << 1)
+
+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;
+}
+
+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_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;
+
+	switch (ioctl) {
+	case KVM_TRACE_ENABLE:
+		r = kvm_trace_enable(argp);
+		break;
+	case KVM_TRACE_DISABLE:
+		r = 0;
+		kvm_trace_cleanup();
+		break;
+	}
+
+	return r;
+}
-- 
1.5.1


--Eric (Liu, Feng)

[-- Attachment #2: 0001-KVM-Add-kvm-trace-support.-when-config-KVM_TRACE-i.patch --]
[-- Type: application/octet-stream, Size: 7566 bytes --]

From 41d65b55580d3f07f9f1c50e89e3d64c5d10fbaf Mon Sep 17 00:00:00 2001
From: Feng (Eric) Liu <eric.e.liu@intel.com>
Date: Tue, 1 Apr 2008 07:26:14 -0400
Subject: [PATCH] KVM: Add kvm trace support. when config KVM_TRACE, it
allows userspace app to read the trace of kvm_related
events through the relayfs.

Signed-off-by: Feng (Eric) Liu <eric.e.liu@intel.com>
---
 arch/x86/kvm/Kconfig  |   10 ++
 arch/x86/kvm/Makefile |    3 +
 virt/kvm/kvm_trace.c  |  245 +++++++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 258 insertions(+), 0 deletions(-)
 create mode 100644 virt/kvm/kvm_trace.c

diff --git a/arch/x86/kvm/Kconfig b/arch/x86/kvm/Kconfig
index 76c70ab..d51ffb3 100644
--- a/arch/x86/kvm/Kconfig
+++ b/arch/x86/kvm/Kconfig
@@ -50,6 +50,16 @@ 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
+	  the relayfs. 
+
 # 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/virt/kvm/kvm_trace.c b/virt/kvm/kvm_trace.c
new file mode 100644
index 0000000..a07760d
--- /dev/null
+++ b/virt/kvm/kvm_trace.c
@@ -0,0 +1,245 @@
+/*
+ * 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.
+ *
+ * Copyright (c) 2008 Intel Corporation
+ *
+ * Authors: 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_CLEARUP 	(1 << 1)
+
+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;
+}
+
+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_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;
+
+	switch (ioctl) {
+	case KVM_TRACE_ENABLE:
+		r = kvm_trace_enable(argp);
+		break;
+	case KVM_TRACE_DISABLE:
+		r = 0;
+		kvm_trace_cleanup();
+		break;
+	}
+
+	return r;
+}
-- 
1.5.1


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Re: [PATCH RFC 2/5] Create relay channels and add trace data

[Avi Kivity]

Liu, Eric E wrote:
> >From 41d65b55580d3f07f9f1c50e89e3d64c5d10fbaf Mon Sep 17 00:00:00 2001
> From: Feng (Eric) Liu <eric.e.liu@intel.com>
> Date: Tue, 1 Apr 2008 07:26:14 -0400
> Subject: [PATCH] KVM: Add kvm trace support. when config KVM_TRACE, it
> allows userspace app to read the trace of kvm_related
> events through the relayfs.
>
>
> +int kvm_trace_ioctl(unsigned int ioctl, unsigned long arg)
> +{
> +	void __user *argp = (void __user *)arg;
> +	long r = -EINVAL;
> +
> +	switch (ioctl) {
> +	case KVM_TRACE_ENABLE:
> +		r = kvm_trace_enable(argp);
> +		break;
> +	case KVM_TRACE_DISABLE:
> +		r = 0;
> +		kvm_trace_cleanup();
> +		break;
> +	}
> +
> +	return r;
> +}
>   

Since we want to allow non-privileged users to open /dev/kvm, and 
tracing can provide data on other users' VMs, we need check on 
CAP_SYS_ADMIN (or maybe CAP_PTRACE?) and return -EPERM if the user is 
not privileged enough.

-- 
error compiling committee.c: too many arguments to function


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Re: [PATCH RFC 2/5] Create relay channels and add trace data

[Liu, Eric E]

Avi Kivity wrote:
> Liu, Eric E wrote:
>>> From 41d65b55580d3f07f9f1c50e89e3d64c5d10fbaf Mon Sep 17 00:00:00
>>> 2001 
>> From: Feng (Eric) Liu <eric.e.liu@intel.com>
>> Date: Tue, 1 Apr 2008 07:26:14 -0400
>> Subject: [PATCH] KVM: Add kvm trace support. when config KVM_TRACE,
>> it allows userspace app to read the trace of kvm_related
>> events through the relayfs.
>> 
>> 
>> +int kvm_trace_ioctl(unsigned int ioctl, unsigned long arg) +{
>> +	void __user *argp = (void __user *)arg;
>> +	long r = -EINVAL;
>> +
>> +	switch (ioctl) {
>> +	case KVM_TRACE_ENABLE:
>> +		r = kvm_trace_enable(argp);
>> +		break;
>> +	case KVM_TRACE_DISABLE:
>> +		r = 0;
>> +		kvm_trace_cleanup();
>> +		break;
>> +	}
>> +
>> +	return r;
>> +}
>> 
> 
> Since we want to allow non-privileged users to open /dev/kvm, and
> tracing can provide data on other users' VMs, we need check on
> CAP_SYS_ADMIN (or maybe CAP_PTRACE?) and return -EPERM if the user is
> not privileged enough.

Thanks for your comments, I think using CAP_SYS_ADMIN is better. 

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