[PATCH v3 2/5] perf kvm: Introduce guest interfaces for sampling callchains

Tianyi Liu
2023-12-10T08:15:25Z

This patch introduces two callback interfaces used between perf and KVM:

- get_unwind_info: Return required data for unwinding at once; including
ip address, frame pointer, whether the guest vCPU is running in 32 or 64
bits, and possibly the base addresses of the segments.

- read_virt: Read data from a virtual address of the guest vm, used for
reading the stack frames from the guest.

Signed-off-by: Tianyi Liu <i.pear@outlook.com>
---
include/linux/perf_event.h | 17 +++++++++++++++++
kernel/events/core.c | 10 ++++++++++
2 files changed, 27 insertions(+)

diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h
index 5547ba68e6e4..dacc1623dcaa 100644
--- a/include/linux/perf_event.h
+++ b/include/linux/perf_event.h
@@ -17,6 +17,8 @@
#include <uapi/linux/perf_event.h>
#include <uapi/linux/bpf_perf_event.h>

+#include <linux/perf_kvm.h>
+
/*
* Kernel-internal data types and definitions:
*/
@@ -32,6 +34,9 @@
struct perf_guest_info_callbacks {
unsigned int (*state)(void);
unsigned long (*get_ip)(void);
+ bool (*get_unwind_info)(struct perf_kvm_guest_unwind_info *info);
+ bool (*read_virt)(unsigned long addr, void *dest,
+ unsigned int len);
unsigned int (*handle_intel_pt_intr)(void);
};

@@ -1500,6 +1505,8 @@ extern struct perf_guest_info_callbacks __rcu *perf_guest_cbs;

DECLARE_STATIC_CALL(__perf_guest_state, *perf_guest_cbs->state);
DECLARE_STATIC_CALL(__perf_guest_get_ip, *perf_guest_cbs->get_ip);
+DECLARE_STATIC_CALL(__perf_guest_get_unwind_info, *perf_guest_cbs->get_unwind_info);
+DECLARE_STATIC_CALL(__perf_guest_read_virt, *perf_guest_cbs->read_virt);
DECLARE_STATIC_CALL(__perf_guest_handle_intel_pt_intr, *perf_guest_cbs->handle_intel_pt_intr);

static inline unsigned int perf_guest_state(void)
@@ -1510,6 +1517,14 @@ static inline unsigned long perf_guest_get_ip(void)
{
return static_call(__perf_guest_get_ip)();
}
+static inline bool perf_guest_get_unwind_info(struct perf_kvm_guest_unwind_info *info)
+{
+ return static_call(__perf_guest_get_unwind_info)(info);
+}
+static inline bool perf_guest_read_virt(unsigned long addr, void *dest, unsigned int length)
+{
+ return static_call(__perf_guest_read_virt)(addr, dest, length);
+}
static inline unsigned int perf_guest_handle_intel_pt_intr(void)
{
return static_call(__perf_guest_handle_intel_pt_intr)();
@@ -1519,6 +1534,8 @@ extern void perf_unregister_guest_info_callbacks(struct perf_guest_info_callback
#else
static inline unsigned int perf_guest_state(void) { return 0; }
static inline unsigned long perf_guest_get_ip(void) { return 0; }
+static inline bool perf_guest_get_unwind_info(struct perf_kvm_guest_unwind_info *) { return 0; }
+static inline bool perf_guest_read_virt(unsigned long, void*, unsigned int) { return 0; }
static inline unsigned int perf_guest_handle_intel_pt_intr(void) { return 0; }
#endif /* CONFIG_GUEST_PERF_EVENTS */

diff --git a/kernel/events/core.c b/kernel/events/core.c
index b704d83a28b2..4c5e35006217 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -6807,6 +6807,8 @@ struct perf_guest_info_callbacks __rcu *perf_guest_cbs;

DEFINE_STATIC_CALL_RET0(__perf_guest_state, *perf_guest_cbs->state);
DEFINE_STATIC_CALL_RET0(__perf_guest_get_ip, *perf_guest_cbs->get_ip);
+DEFINE_STATIC_CALL_RET0(__perf_guest_get_unwind_info, *perf_guest_cbs->get_unwind_info);
+DEFINE_STATIC_CALL_RET0(__perf_guest_read_virt, *perf_guest_cbs->read_virt);
DEFINE_STATIC_CALL_RET0(__perf_guest_handle_intel_pt_intr, *perf_guest_cbs->handle_intel_pt_intr);

void perf_register_guest_info_callbacks(struct perf_guest_info_callbacks *cbs)
@@ -6818,6 +6820,12 @@ void perf_register_guest_info_callbacks(struct perf_guest_info_callbacks *cbs)
static_call_update(__perf_guest_state, cbs->state);
static_call_update(__perf_guest_get_ip, cbs->get_ip);

+ if (cbs->get_unwind_info)
+ static_call_update(__perf_guest_get_unwind_info, cbs->get_unwind_info);
+
+ if (cbs->read_virt)
+ static_call_update(__perf_guest_read_virt, cbs->read_virt);
+
/* Implementing ->handle_intel_pt_intr is optional. */
if (cbs->handle_intel_pt_intr)
static_call_update(__perf_guest_handle_intel_pt_intr,
@@ -6833,6 +6841,8 @@ void perf_unregister_guest_info_callbacks(struct perf_guest_info_callbacks *cbs)
rcu_assign_pointer(perf_guest_cbs, NULL);
static_call_update(__perf_guest_state, (void *)&__static_call_return0);
static_call_update(__perf_guest_get_ip, (void *)&__static_call_return0);
+ static_call_update(__perf_guest_get_unwind_info, (void *)&__static_call_return0);
+ static_call_update(__perf_guest_read_virt, (void *)&__static_call_return0);
static_call_update(__perf_guest_handle_intel_pt_intr,
(void *)&__static_call_return0);
synchronize_rcu();
--
2.34.1