[PATCH v6 0/8] KVM perf support

[Anup Patel]

On Tue, Feb 7, 2023 at 3:26 PM Atish Patra <atishp at rivosinc.com> wrote:
>
> This series extends perf support for KVM. The KVM implementation relies
> on the SBI PMU extension and trap n emulation of hpmcounter CSRs.
> The KVM implementation exposes the virtual counters to the guest and internally
> manage the counters using kernel perf counters.
>
> This series doesn't support the counter overflow as the Sscofpmf extension
> doesn't allow trap & emulation mechanism of scountovf CSR yet. The required
> changes to allow that are being under discussions. Supporting overflow interrupt
> also requires AIA interrupt filtering support.
>
> perf stat works in kvm guests with this series.
>
> Here is example of running perf stat in a guest running in KVM.
>
> ===========================================================================
> / # /host/apps/perf stat -e instructions -e cycles -e r8000000000000005 \
> > -e r8000000000000006 -e r8000000000000007 -e r8000000000000008 \
> > -e r800000000000000a perf bench sched messaging -g 10 -l 10
>
> # Running 'sched/messaging' benchmark:
> # 20 sender and receiver processes per group
> # 10 groups == 400 processes run
>
>      Total time: 7.769 [sec]
>
>  Performance counter stats for 'perf bench sched messaging -g 10 -l 10':
>
>        73556259604      cycles
>        73387266056      instructions              #    1.00  insn per cycle
>                  0      dTLB-store-misses
>                  0      iTLB-load-misses
>                  0      r8000000000000005
>               2595      r8000000000000006
>               2272      r8000000000000007
>                 10      r8000000000000008
>                  0      r800000000000000a
>
>       12.173720400 seconds time elapsed
>
>        1.002716000 seconds user
>       21.931047000 seconds sys
>
>
> Note: The SBI_PMU_FW_SET_TIMER (eventid : r8000000000000005) is zero
> as kvm guest supports sstc now.
>
> This series can be found here as well.
> https://github.com/atishp04/linux/tree/kvm_perf_v6
>
> TODO:
> 1. Add sscofpmf support.
> 2. Add One reg interface for the following operations:
>         1. Enable/Disable PMU (should it at VM level rather than vcpu ?)
>         2. Number of hpmcounter and width of the counters
>         3. Init PMU
>         4. Allow guest user to access cycle & instret without trapping
> 3. Move counter mask to a bitmask instead of unsigned long so that it can work
>    for RV32 systems where number of total counters are more than 32.
>    This will also accomodate future systems which may define maximum counters
>    to be more than 64.
>
> Changes from v5->v6:
> 1. Addressed remainig RB tags.
> 2. Rebased on kvm-queue which already has merged first 6 patches from v5.
> 3. Added static time compilation checks for max counters.
> 4. Addressed other nit comments.
>
> Changes from v4->v5:
> 1. Few checkpatch --strict error fixes.
> 2. Some other minor nit comment addressed.
> 3. Fixed an issue around counter indexing.
>
> Changes from v3->v4:
> 1. Addressed all the comments on v3.
> 2. Modified the vcpu_pmu_init to void return type.
> 3. Redirect illegal instruction trap to guest for invalid hpmcounter access
>    instead of exiting to the userpsace.
> 4. Got rid of unecessary error messages.
>
> Changes v2->v3:
> 1. Changed the exported functions to GPL only export.
> 2. Addressed all the nit comments on v2.
> 3. Split non-kvm related changes into separate patches.
> 4. Reorgainze the PATCH 11 and 10 based on Drew's suggestions.
>
> Changes from v1->v2:
> 1. Addressed comments from Andrew.
> 2. Removed kvpmu sanity check.
> 3. Added a kvm pmu init flag and the sanity check to probe function.
> 4. Improved the linux vs sbi error code handling.
>
>
> Atish Patra (8):
> RISC-V: KVM: Add skeleton support for perf
> RISC-V: KVM: Add SBI PMU extension support
> RISC-V: KVM: Make PMU functionality depend on Sscofpmf
> RISC-V: KVM: Disable all hpmcounter access for VS/VU mode
> RISC-V: KVM: Implement trap & emulate for hpmcounters
> RISC-V: KVM: Implement perf support without sampling
> RISC-V: KVM: Support firmware events
> RISC-V: KVM: Increment firmware pmu events

I have queued this series for Linux-6.3

Thanks,
Anup

>
> arch/riscv/include/asm/kvm_host.h     |   4 +
> arch/riscv/include/asm/kvm_vcpu_pmu.h | 108 +++++
> arch/riscv/kvm/Makefile               |   1 +
> arch/riscv/kvm/main.c                 |   3 +-
> arch/riscv/kvm/tlb.c                  |   4 +
> arch/riscv/kvm/vcpu.c                 |   7 +
> arch/riscv/kvm/vcpu_insn.c            |   4 +-
> arch/riscv/kvm/vcpu_pmu.c             | 630 ++++++++++++++++++++++++++
> arch/riscv/kvm/vcpu_sbi.c             |  11 +
> arch/riscv/kvm/vcpu_sbi_pmu.c         |  86 ++++
> arch/riscv/kvm/vcpu_sbi_replace.c     |   7 +
> 11 files changed, 863 insertions(+), 2 deletions(-)
> create mode 100644 arch/riscv/include/asm/kvm_vcpu_pmu.h
> create mode 100644 arch/riscv/kvm/vcpu_pmu.c
> create mode 100644 arch/riscv/kvm/vcpu_sbi_pmu.c
>
> --
> 2.25.1
>