Re: [PATCH v3 8/9] RISC-V: KVM: Implement get event info function

[Anup Patel <anup@brainfault.org>]

On Fri, May 23, 2025 at 12:33 AM Atish Patra <atishp@rivosinc.com> wrote:
>
> The new get_event_info funciton allows the guest to query the presence
> of multiple events with single SBI call. Currently, the perf driver
> in linux guest invokes it for all the standard SBI PMU events. Support
> the SBI function implementation in KVM as well.
>
> Signed-off-by: Atish Patra <atishp@rivosinc.com>

LGTM.

Reviewed-by: Anup Patel <anup@brainfault.org>

Regards,
Anup

> ---
>  arch/riscv/include/asm/kvm_vcpu_pmu.h |  3 ++
>  arch/riscv/kvm/vcpu_pmu.c             | 66 +++++++++++++++++++++++++++++++++++
>  arch/riscv/kvm/vcpu_sbi_pmu.c         |  3 ++
>  3 files changed, 72 insertions(+)
>
> diff --git a/arch/riscv/include/asm/kvm_vcpu_pmu.h b/arch/riscv/include/asm/kvm_vcpu_pmu.h
> index 1d85b6617508..9a930afc8f57 100644
> --- a/arch/riscv/include/asm/kvm_vcpu_pmu.h
> +++ b/arch/riscv/include/asm/kvm_vcpu_pmu.h
> @@ -98,6 +98,9 @@ void kvm_riscv_vcpu_pmu_init(struct kvm_vcpu *vcpu);
>  int kvm_riscv_vcpu_pmu_snapshot_set_shmem(struct kvm_vcpu *vcpu, unsigned long saddr_low,
>                                       unsigned long saddr_high, unsigned long flags,
>                                       struct kvm_vcpu_sbi_return *retdata);
> +int kvm_riscv_vcpu_pmu_event_info(struct kvm_vcpu *vcpu, unsigned long saddr_low,
> +                                 unsigned long saddr_high, unsigned long num_events,
> +                                 unsigned long flags, struct kvm_vcpu_sbi_return *retdata);
>  void kvm_riscv_vcpu_pmu_deinit(struct kvm_vcpu *vcpu);
>  void kvm_riscv_vcpu_pmu_reset(struct kvm_vcpu *vcpu);
>
> diff --git a/arch/riscv/kvm/vcpu_pmu.c b/arch/riscv/kvm/vcpu_pmu.c
> index 163bd4403fd0..70a6bdfc42f5 100644
> --- a/arch/riscv/kvm/vcpu_pmu.c
> +++ b/arch/riscv/kvm/vcpu_pmu.c
> @@ -453,6 +453,72 @@ int kvm_riscv_vcpu_pmu_snapshot_set_shmem(struct kvm_vcpu *vcpu, unsigned long s
>         return 0;
>  }
>
> +int kvm_riscv_vcpu_pmu_event_info(struct kvm_vcpu *vcpu, unsigned long saddr_low,
> +                                 unsigned long saddr_high, unsigned long num_events,
> +                                 unsigned long flags, struct kvm_vcpu_sbi_return *retdata)
> +{
> +       struct riscv_pmu_event_info *einfo;
> +       int shmem_size = num_events * sizeof(*einfo);
> +       gpa_t shmem;
> +       u32 eidx, etype;
> +       u64 econfig;
> +       int ret;
> +
> +       if (flags != 0 || (saddr_low & (SZ_16 - 1))) {
> +               ret = SBI_ERR_INVALID_PARAM;
> +               goto out;
> +       }
> +
> +       shmem = saddr_low;
> +       if (saddr_high != 0) {
> +               if (IS_ENABLED(CONFIG_32BIT)) {
> +                       shmem |= ((gpa_t)saddr_high << 32);
> +               } else {
> +                       ret = SBI_ERR_INVALID_ADDRESS;
> +                       goto out;
> +               }
> +       }
> +
> +       if (kvm_vcpu_validate_gpa_range(vcpu, shmem, shmem_size, true)) {
> +               ret = SBI_ERR_INVALID_ADDRESS;
> +               goto out;
> +       }
> +
> +       einfo = kzalloc(shmem_size, GFP_KERNEL);
> +       if (!einfo)
> +               return -ENOMEM;
> +
> +       ret = kvm_vcpu_read_guest(vcpu, shmem, einfo, shmem_size);
> +       if (ret) {
> +               ret = SBI_ERR_FAILURE;
> +               goto free_mem;
> +       }
> +
> +       for (int i = 0; i < num_events; i++) {
> +               eidx = einfo[i].event_idx;
> +               etype = kvm_pmu_get_perf_event_type(eidx);
> +               econfig = kvm_pmu_get_perf_event_config(eidx, einfo[i].event_data);
> +               ret = riscv_pmu_get_event_info(etype, econfig, NULL);
> +               if (ret > 0)
> +                       einfo[i].output = 1;
> +               else
> +                       einfo[i].output = 0;
> +       }
> +
> +       kvm_vcpu_write_guest(vcpu, shmem, einfo, shmem_size);
> +       if (ret) {
> +               ret = SBI_ERR_FAILURE;
> +               goto free_mem;
> +       }
> +
> +free_mem:
> +       kfree(einfo);
> +out:
> +       retdata->err_val = ret;
> +
> +       return 0;
> +}
> +
>  int kvm_riscv_vcpu_pmu_num_ctrs(struct kvm_vcpu *vcpu,
>                                 struct kvm_vcpu_sbi_return *retdata)
>  {
> diff --git a/arch/riscv/kvm/vcpu_sbi_pmu.c b/arch/riscv/kvm/vcpu_sbi_pmu.c
> index e4be34e03e83..a020d979d179 100644
> --- a/arch/riscv/kvm/vcpu_sbi_pmu.c
> +++ b/arch/riscv/kvm/vcpu_sbi_pmu.c
> @@ -73,6 +73,9 @@ static int kvm_sbi_ext_pmu_handler(struct kvm_vcpu *vcpu, struct kvm_run *run,
>         case SBI_EXT_PMU_SNAPSHOT_SET_SHMEM:
>                 ret = kvm_riscv_vcpu_pmu_snapshot_set_shmem(vcpu, cp->a0, cp->a1, cp->a2, retdata);
>                 break;
> +       case SBI_EXT_PMU_EVENT_GET_INFO:
> +               ret = kvm_riscv_vcpu_pmu_event_info(vcpu, cp->a0, cp->a1, cp->a2, cp->a3, retdata);
> +               break;
>         default:
>                 retdata->err_val = SBI_ERR_NOT_SUPPORTED;
>         }
>
> --
> 2.43.0
>