On Sat, Apr 20, 2024 at 5:17 AM Atish Patra <atishp@xxxxxxxxxxxx> wrote: > > This series implements SBI PMU improvements done in SBI v2.0[1] i.e. PMU snapshot > and fw_read_hi() functions. > > SBI v2.0 introduced PMU snapshot feature which allows the SBI implementation > to provide counter information (i.e. values/overflow status) via a shared > memory between the SBI implementation and supervisor OS. This allows to minimize > the number of traps in when perf being used inside a kvm guest as it relies on > SBI PMU + trap/emulation of the counters. > > The current set of ratified RISC-V specification also doesn't allow scountovf > to be trap/emulated by the hypervisor. The SBI PMU snapshot bridges the gap > in ISA as well and enables perf sampling in the guest. However, LCOFI in the > guest only works via IRQ filtering in AIA specification. That's why, AIA > has to be enabled in the hardware (at least the Ssaia extension) in order to > use the sampling support in the perf. > > Here are the patch wise implementation details. > > PATCH 1,4,7,8,9,10,11,15 : Generic cleanups/improvements. > PATCH 2,3,14 : FW_READ_HI function implementation > PATCH 5-6: Add PMU snapshot feature in sbi pmu driver > PATCH 12-13: KVM implementation for snapshot and sampling in kvm guests > PATCH 16-17: Generic improvements for kvm selftests > PATCH 18-22: KVM selftests for SBI PMU extension > > The series is based on v6.9-rc4 and is available at: > > https://github.com/atishp04/linux/tree/kvm_pmu_snapshot_v8 > > The kvmtool patch is also available at: > https://github.com/atishp04/kvmtool/tree/sscofpmf > > It also requires Ssaia ISA extension to be present in the hardware in order to > get perf sampling support in the guest. In Qemu virt machine, it can be done > by the following config. > > ``` > -cpu rv64,sscofpmf=true,x-ssaia=true > ``` > > There is no other dependencies on AIA apart from that. Thus, Ssaia must be disabled > for the guest if AIA patches are not available. Here is the example command. > > ``` > ./lkvm-static run -m 256 -c2 --console serial -p "console=ttyS0 earlycon" --disable-ssaia -k ./Image --debug > ``` > > The series has been tested only in Qemu. > Here is the snippet of the perf running inside a kvm guest. > > =================================================== > $ perf record -e cycles -e instructions perf bench sched messaging -g 5 > ... > $ Running 'sched/messaging' benchmark: > ... > [ 45.928723] perf_duration_warn: 2 callbacks suppressed > [ 45.929000] perf: interrupt took too long (484426 > 483186), lowering kernel.perf_event_max_sample_rate to 250 > $ 20 sender and receiver processes per group > $ 5 groups == 200 processes run > > Total time: 14.220 [sec] > [ perf record: Woken up 1 times to write data ] > [ perf record: Captured and wrote 0.117 MB perf.data (1942 samples) ] > $ perf report --stdio > $ To display the perf.data header info, please use --header/--header-only optio> > $ > $ > $ Total Lost Samples: 0 > $ > $ Samples: 943 of event 'cycles' > $ Event count (approx.): 5128976844 > $ > $ Overhead Command Shared Object Symbol > > $ ........ ............... ........................... .....................> > $ > 7.59% sched-messaging [kernel.kallsyms] [k] memcpy > 5.48% sched-messaging [kernel.kallsyms] [k] percpu_counter_ad> > 5.24% sched-messaging [kernel.kallsyms] [k] __sbi_rfence_v02_> > 4.00% sched-messaging [kernel.kallsyms] [k] _raw_spin_unlock_> > 3.79% sched-messaging [kernel.kallsyms] [k] set_pte_range > 3.72% sched-messaging [kernel.kallsyms] [k] next_uptodate_fol> > 3.46% sched-messaging [kernel.kallsyms] [k] filemap_map_pages > 3.31% sched-messaging [kernel.kallsyms] [k] handle_mm_fault > 3.20% sched-messaging [kernel.kallsyms] [k] finish_task_switc> > 3.16% sched-messaging [kernel.kallsyms] [k] clear_page > 3.03% sched-messaging [kernel.kallsyms] [k] mtree_range_walk > 2.42% sched-messaging [kernel.kallsyms] [k] flush_icache_pte > > =================================================== > > [1] https://github.com/riscv-non-isa/riscv-sbi-doc > > Changes from v7->v8: > 1. Updated event states so that shared memory is updated only during stop > operations. > 2. Avoid clobbering lower XLEN counter/overflow values in shared memory > by maintaining a temporary copy for RV32. > 3. Improved overflow handling in snapshot case by supporting all 64 values. > 4. Minor cleanups based on suggestions on v7. > > Changes from v6->v7: > 1. Used SBI_SHMEM_DISABLE in the driver. > 2. Added RB Tags. > 3. Improved the sbi_pmu_test commandline to allow disabling multiple > tests. > > Changes from v5->v6: > 1. Added a patch for command line option for the sbi pmu tests. > 2. Removed redundant prints and restructure the code little bit. > 3. Added a patch for computing the sbi minor version correctly. > 4. Addressed all other comments on v5. > > Changes from v4->v5: > 1. Moved sbi related definitions to its own header file from processor.h > 2. Added few helper functions for selftests. > 3. Improved firmware counter read and RV32 start/stop functions. > 4. Converted all the shifting operations to use BIT macro > 5. Addressed all other comments on v4. > > Changes from v3->v4: > 1. Added selftests. > 2. Fixed an issue to clear the interrupt pending bits. > 3. Fixed the counter index in snapshot memory start function. > > Changes from v2->v3: > 1. Fixed a patchwork warning on patch6. > 2. Fixed a comment formatting & nit fix in PATCH 3 & 5. > 3. Moved the hvien update and sscofpmf enabling to PATCH 9 from PATCH 8. > > Changes from v1->v2: > 1. Fixed warning/errors from patchwork CI. > 2. Rebased on top of kvm-next. > 3. Added Acked-by tags. > > Changes from RFC->v1: > 1. Addressed all the comments on RFC series. > 2. Removed PATCH2 and merged into later patches. > 3. Added 2 more patches for minor fixes. > 4. Fixed KVM boot issue without Ssaia and made sscofpmf in guest dependent on > Ssaia in the host. > > Atish Patra (24): > RISC-V: Fix the typo in Scountovf CSR name > RISC-V: Add FIRMWARE_READ_HI definition > drivers/perf: riscv: Read upper bits of a firmware counter > drivers/perf: riscv: Use BIT macro for shifting operations > RISC-V: Add SBI PMU snapshot definitions > RISC-V: KVM: Rename the SBI_STA_SHMEM_DISABLE to a generic name > RISC-V: Use the minor version mask while computing sbi version > drivers/perf: riscv: Fix counter mask iteration for RV32 > drivers/perf: riscv: Implement SBI PMU snapshot function > RISC-V: KVM: Fix the initial sample period value > RISC-V: KVM: No need to update the counter value during reset > RISC-V: KVM: No need to exit to the user space if perf event failed > RISC-V: KVM: Implement SBI PMU Snapshot feature > RISC-V: KVM: Add perf sampling support for guests > RISC-V: KVM: Support 64 bit firmware counters on RV32 > RISC-V: KVM: Improve firmware counter read function > KVM: riscv: selftests: Move sbi definitions to its own header file > KVM: riscv: selftests: Add helper functions for extension checks > KVM: riscv: selftests: Add Sscofpmf to get-reg-list test > KVM: riscv: selftests: Add SBI PMU extension definitions > KVM: riscv: selftests: Add SBI PMU selftest > KVM: riscv: selftests: Add a test for PMU snapshot functionality > KVM: riscv: selftests: Add a test for counter overflow > KVM: riscv: selftests: Add commandline option for SBI PMU test Queued this series for Linux-6.10 If new issues are discovered then send patches based on the KVM riscv queue. Thanks, Anup > > arch/riscv/include/asm/csr.h | 5 +- > arch/riscv/include/asm/kvm_vcpu_pmu.h | 16 +- > arch/riscv/include/asm/sbi.h | 38 +- > arch/riscv/include/uapi/asm/kvm.h | 1 + > arch/riscv/kernel/paravirt.c | 6 +- > arch/riscv/kvm/aia.c | 5 + > arch/riscv/kvm/vcpu.c | 15 +- > arch/riscv/kvm/vcpu_onereg.c | 6 + > arch/riscv/kvm/vcpu_pmu.c | 260 ++++++- > arch/riscv/kvm/vcpu_sbi_pmu.c | 17 +- > arch/riscv/kvm/vcpu_sbi_sta.c | 4 +- > drivers/perf/riscv_pmu.c | 1 + > drivers/perf/riscv_pmu_sbi.c | 309 +++++++- > include/linux/perf/riscv_pmu.h | 6 + > tools/testing/selftests/kvm/Makefile | 1 + > .../selftests/kvm/include/riscv/processor.h | 49 +- > .../testing/selftests/kvm/include/riscv/sbi.h | 141 ++++ > .../selftests/kvm/include/riscv/ucall.h | 1 + > .../selftests/kvm/lib/riscv/processor.c | 12 + > .../testing/selftests/kvm/riscv/arch_timer.c | 2 +- > .../selftests/kvm/riscv/get-reg-list.c | 4 + > .../selftests/kvm/riscv/sbi_pmu_test.c | 681 ++++++++++++++++++ > tools/testing/selftests/kvm/steal_time.c | 4 +- > 23 files changed, 1467 insertions(+), 117 deletions(-) > create mode 100644 tools/testing/selftests/kvm/include/riscv/sbi.h > create mode 100644 tools/testing/selftests/kvm/riscv/sbi_pmu_test.c > > -- > 2.34.1 >
