[PATCH v3 0/2] perf kvm: Add kvm stat support on riscv

[Shenlin Liang]

'perf kvm stat report/record' generates a statistical analysis of KVM
events and can be used to analyze guest exit reasons. This patch tries
to add stat support on riscv.

Map the return value of trace_kvm_exit() to the specific cause of the 
exception, and export it to userspace.

It records on two available KVM tracepoints for riscv: "kvm:kvm_entry"
and "kvm:kvm_exit", and reports statistical data which includes events
handles time, samples, and so on.

Cross compiling perf in X86 environment may encounter issues with missing
libraries and tools. Suggest compiling nativly in RISC-V environment

Simple tests go below:

# ./perf kvm record -e "kvm:kvm_entry" -e "kvm:kvm_exit"
Lowering default frequency rate from 4000 to 2500.
Please consider tweaking /proc/sys/kernel/perf_event_max_sample_rate.
[ perf record: Woken up 18 times to write data ]
[ perf record: Captured and wrote 5.433 MB perf.data.guest (62519 samples) 

# ./perf kvm report
31K kvm:kvm_entry
31K kvm:kvm_exit

# ./perf kvm stat record -a
[ perf record: Woken up 3 times to write data ]
[ perf record: Captured and wrote 8.502 MB perf.data.guest (99338 samples) ]

# ./perf kvm stat report --event=vmexit
Event name                Samples   Sample%    Time (ns)     Time%   Max Time (ns)   Min Time (ns)  Mean Time (ns)
STORE_GUEST_PAGE_FAULT     26968     54.00%    2003031800    40.00%     3361400         27600          74274
LOAD_GUEST_PAGE_FAULT      17645     35.00%    1153338100    23.00%     2513400         30800          65363
VIRTUAL_INST_FAULT         1247      2.00%     340820800     6.00%      1190800         43300          273312
INST_GUEST_PAGE_FAULT      1128      2.00%     340645800     6.00%      2123200         30200          301990
SUPERVISOR_SYSCALL         1019      2.00%     245989900     4.00%      1851500         29300          241403
LOAD_ACCESS                986       1.00%     671556200     13.00%     4180200         100700         681091
INST_ACCESS                655       1.00%     170054800     3.00%      1808300         54600          259625
HYPERVISOR_SYSCALL         21        0.00%     4276400       0.00%      716500          116000         203638 

Changes from v1->v2:
- Rebased on Linux 6.9-rc3.

Changes from v2->v3:
- Add the missing assignment for 'vcpu_id_str' in patch 2.
- Remove parentheses that cause compilation errors

Shenlin Liang (2):
  RISCV: KVM: add tracepoints for entry and exit events
  perf kvm/riscv: Port perf kvm stat to RISC-V

 arch/riscv/kvm/trace.h                        | 67 ++++++++++++++++
 arch/riscv/kvm/vcpu.c                         |  7 ++
 tools/perf/arch/riscv/Makefile                |  1 +
 tools/perf/arch/riscv/util/Build              |  1 +
 tools/perf/arch/riscv/util/kvm-stat.c         | 79 +++++++++++++++++++
 .../arch/riscv/util/riscv_exception_types.h   | 35 ++++++++
 6 files changed, 190 insertions(+)
 create mode 100644 arch/riscv/kvm/trace.h
 create mode 100644 tools/perf/arch/riscv/util/kvm-stat.c
 create mode 100644 tools/perf/arch/riscv/util/riscv_exception_types.h

-- 
2.37.2