Hi there,
This series of patches enables callchains for guests (used by perf kvm),
which holds the top spot on the perf wiki TODO list [1]. This allows users
to perform guest OS callchain or performance analysis from external
using PMU events.
The event processing flow is as follows (shown as backtrace):
#0 kvm_arch_vcpu_get_frame_pointer / kvm_arch_vcpu_read_virt (per arch)
#1 kvm_guest_get_frame_pointer / kvm_guest_read_virt
<callback function pointers in `struct perf_guest_info_callbacks`>
#2 perf_guest_get_frame_pointer / perf_guest_read_virt
#3 perf_callchain_guest
#4 get_perf_callchain
#5 perf_callchain
Between #0 and #1 is the interface between KVM and the arch-specific
impl, while between #1 and #2 is the interface between Perf and KVM.
The 1st patch implements #0. The 2nd patch extends interfaces between #1
and #2, while the 3rd patch implements #1. The 4th patch implements #3
and modifies #4 #5. The last patch is for userspace utils.
Since arm64 hasn't provided some foundational infrastructure (interface
for reading from a virtual address of guest), the arm64 implementation
is stubbed for now because it's a bit complex, and will be implemented
later.
Tested with both 32-bit and 64-bit guest operating systems / unikernels,
that `perf script` could correctly show the certain callchains.
FlameGraphs can also be generated with this series of patches and [2].
Any feedback will be greatly appreciated.
[1] https://perf.wiki.kernel.org/index.php/Todo
[2] https://github.com/brendangregg/FlameGraph
v1:
https://lore.kernel.org/kvm/SYYP282MB108686A73C0F896D90D246569DE5A@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx/
Changes since v1:
- v1 only includes partial KVM modifications, while v2 is a complete
implementation. Also updated based on Sean's feedback.
Tianyi Liu (5):
KVM: Add arch specific interfaces for sampling guest callchains
perf kvm: Introduce guest interfaces for sampling callchains
KVM: implement new perf interfaces
perf kvm: Support sampling guest callchains
perf tools: Support PERF_CONTEXT_GUEST_* flags
arch/arm64/kvm/arm.c | 17 +++++++++
arch/x86/events/core.c | 56 +++++++++++++++++++++++------
arch/x86/kvm/x86.c | 18 ++++++++++
include/linux/kvm_host.h | 4 +++
include/linux/perf_event.h | 18 +++++++++-
kernel/bpf/stackmap.c | 8 ++---
kernel/events/callchain.c | 27 +++++++++++++-
kernel/events/core.c | 17 ++++++++-
tools/perf/builtin-timechart.c | 6 ++++
tools/perf/util/data-convert-json.c | 6 ++++
tools/perf/util/machine.c | 6 ++++
virt/kvm/kvm_main.c | 25 +++++++++++++
12 files changed, 191 insertions(+), 17 deletions(-)
base-commit: 8a749fd1a8720d4619c91c8b6e7528c0a355c0aa
--
2.42.0
