[PATCH v4 0/2] riscv: Add perf support to collect KVM guest statistics from host side

[zhouquan at iscas.ac.cn]

From: Quan Zhou <zhouquan at iscas.ac.cn>

Add basic guest support to RISC-V perf, enabling it to distinguish
whether PMU interrupts occur in the host or the guest, and then
collect some basic guest information from the host side
(guest os callchain is not supported for now).

Based on the x86/arm implementation, tested with kvm-riscv.
test env:
- host: qemu-9.0.0
- guest: qemu-9.0.0 --enable-kvm (only start one guest and run top)

-----------------------------------------
1) perf kvm top
./perf kvm --host --guest \
  --guestkallsyms=/<path-to-kallsyms> \
  --guestmodules=/<path-to-modules> top

PerfTop:      41 irqs/sec  kernel:97.6% us: 0.0% guest kernel: 0.0% guest us: 0.0% exact:  0.0% [250Hz cycles:P],  (all, 4 CPUs)
-------------------------------------------------------------------------------

    64.57%  [kernel]        [k] default_idle_call
     3.12%  [kernel]        [k] _raw_spin_unlock_irqrestore
     3.03%  [guest.kernel]  [g] mem_serial_out
     2.61%  [kernel]        [k] handle_softirqs
     2.32%  [kernel]        [k] do_trap_ecall_u
     1.71%  [kernel]        [k] _raw_spin_unlock_irq
     1.26%  [guest.kernel]  [g] do_raw_spin_lock
     1.25%  [kernel]        [k] finish_task_switch.isra.0
     1.16%  [kernel]        [k] do_idle
     0.77%  libc.so.6       [.] ioctl
     0.76%  [kernel]        [k] queue_work_on
     0.69%  [kernel]        [k] __local_bh_enable_ip
     0.67%  [guest.kernel]  [g] __noinstr_text_start
     0.64%  [guest.kernel]  [g] mem_serial_in
     0.41%  libc.so.6       [.] pthread_sigmask
     0.39%  [kernel]        [k] mem_cgroup_uncharge_skmem
     0.39%  [kernel]        [k] __might_resched
     0.39%  [guest.kernel]  [g] _nohz_idle_balance.isra.0
     0.37%  [kernel]        [k] sched_balance_update_blocked_averages
     0.34%  [kernel]        [k] sched_balance_rq

2) perf kvm record
./perf kvm --host --guest \
  --guestkallsyms=/<path-to-kallsyms> \
  --guestmodules=/<path-to-modules> record -a sleep 60

[ perf record: Woken up 3 times to write data ]
[ perf record: Captured and wrote 1.292 MB perf.data.kvm (17990 samples) ]

3) perf kvm report
./perf kvm --host --guest \
  --guestkallsyms=/<path-to-kallsyms> \
  --guestmodules=/<path-to-modules> report -i perf.data.kvm

# Total Lost Samples: 0
#
# Samples: 17K of event 'cycles:P'
# Event count (approx.): 269968947184
#
# Overhead  Command          Shared Object            Symbol                                        
# ........  ...............  .......................  ..............................................
#
    61.86%  swapper          [kernel.kallsyms]        [k] default_idle_call
     2.93%  :6463            [guest.kernel.kallsyms]  [g] do_raw_spin_lock
     2.82%  :6462            [guest.kernel.kallsyms]  [g] mem_serial_out
     2.11%  sshd             [kernel.kallsyms]        [k] _raw_spin_unlock_irqrestore
     1.78%  :6462            [guest.kernel.kallsyms]  [g] do_raw_spin_lock
     1.37%  swapper          [kernel.kallsyms]        [k] handle_softirqs
     1.36%  swapper          [kernel.kallsyms]        [k] do_idle
     1.21%  sshd             [kernel.kallsyms]        [k] do_trap_ecall_u
     1.21%  sshd             [kernel.kallsyms]        [k] _raw_spin_unlock_irq
     1.11%  qemu-system-ris  [kernel.kallsyms]        [k] do_trap_ecall_u
     0.93%  qemu-system-ris  libc.so.6                [.] ioctl
     0.89%  sshd             [kernel.kallsyms]        [k] __local_bh_enable_ip
     0.77%  qemu-system-ris  [kernel.kallsyms]        [k] _raw_spin_unlock_irqrestore
     0.68%  qemu-system-ris  [kernel.kallsyms]        [k] queue_work_on
     0.65%  sshd             [kernel.kallsyms]        [k] handle_softirqs
     0.44%  :6462            [guest.kernel.kallsyms]  [g] mem_serial_in
     0.42%  sshd             libc.so.6                [.] pthread_sigmask
     0.34%  :6462            [guest.kernel.kallsyms]  [g] serial8250_tx_chars
     0.30%  swapper          [kernel.kallsyms]        [k] finish_task_switch.isra.0
     0.29%  swapper          [kernel.kallsyms]        [k] sched_balance_rq
     0.29%  sshd             [kernel.kallsyms]        [k] __might_resched
     0.26%  swapper          [kernel.kallsyms]        [k] tick_nohz_idle_exit
     0.26%  swapper          [kernel.kallsyms]        [k] sched_balance_update_blocked_averages
     0.26%  swapper          [kernel.kallsyms]        [k] _nohz_idle_balance.isra.0
     0.24%  qemu-system-ris  [kernel.kallsyms]        [k] finish_task_switch.isra.0
     0.23%  :6462            [guest.kernel.kallsyms]  [g] __noinstr_text_start

---
Change since v3:
- Rebased on v6.12-rc3

Change since v2:
- Rebased on v6.11-rc7
- Keep the misc type consistent with other architectures as `unsigned long` (Andrew)
- Add the same comment for `kvm_arch_pmi_in_guest` as in arm64. (Andrew)

Change since v1:
- Rebased on v6.11-rc3
- Fix incorrect misc type (Andrew)

---
v3 link:
https://lore.kernel.org/all/cover.1726126795.git.zhouquan@iscas.ac.cn/
v2 link:
https://lore.kernel.org/all/cover.1723518282.git.zhouquan@iscas.ac.cn/
v1 link:
https://lore.kernel.org/all/cover.1721271251.git.zhouquan@iscas.ac.cn/

Quan Zhou (2):
  riscv: perf: add guest vs host distinction
  riscv: KVM: add basic support for host vs guest profiling

 arch/riscv/include/asm/kvm_host.h   | 10 ++++++++
 arch/riscv/include/asm/perf_event.h |  6 +++++
 arch/riscv/kernel/perf_callchain.c  | 38 +++++++++++++++++++++++++++++
 arch/riscv/kvm/Kconfig              |  1 +
 arch/riscv/kvm/main.c               | 12 +++++++--
 arch/riscv/kvm/vcpu.c               |  7 ++++++
 6 files changed, 72 insertions(+), 2 deletions(-)


base-commit: 8e929cb546ee42c9a61d24fae60605e9e3192354
-- 
2.34.1