[v2,00/11] KVM perf support

Message

Atish Kumar Patra Dec. 15, 2022, 5 p.m. UTC

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.

1. PATCH1-4 are generic KVM/PMU driver improvements.
2. PATCH8 disables hpmcounter for now. It will be enabled to maintain ABI
requirement once the ONE reg interface is settled. 

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_v2

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

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 (11):
RISC-V: Define helper functions expose hpm counter width and count
RISC-V: KVM: Define a probe function for SBI extension data structures
RISC-V: KVM: Return correct code for hsm stop function
RISC-V: KVM: Modify SBI extension handler to return SBI error code
RISC-V: KVM: Improve privilege mode filtering for perf
RISC-V: KVM: Add skeleton support for perf
RISC-V: KVM: Add SBI PMU extension support
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: Implement firmware events

arch/riscv/include/asm/kvm_host.h     |   3 +
arch/riscv/include/asm/kvm_vcpu_pmu.h | 108 +++++
arch/riscv/include/asm/kvm_vcpu_sbi.h |  13 +-
arch/riscv/include/asm/sbi.h          |   2 +-
arch/riscv/kvm/Makefile               |   1 +
arch/riscv/kvm/main.c                 |   3 +-
arch/riscv/kvm/tlb.c                  |   6 +-
arch/riscv/kvm/vcpu.c                 |   5 +
arch/riscv/kvm/vcpu_insn.c            |   4 +-
arch/riscv/kvm/vcpu_pmu.c             | 585 ++++++++++++++++++++++++++
arch/riscv/kvm/vcpu_sbi.c             |  56 ++-
arch/riscv/kvm/vcpu_sbi_base.c        |  45 +-
arch/riscv/kvm/vcpu_sbi_hsm.c         |  22 +-
arch/riscv/kvm/vcpu_sbi_pmu.c         |  86 ++++
arch/riscv/kvm/vcpu_sbi_replace.c     |  51 ++-
drivers/perf/riscv_pmu_sbi.c          |  62 ++-
include/linux/perf/riscv_pmu.h        |   5 +
17 files changed, 963 insertions(+), 94 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