Re: [PATCH v2 05/11] RISC-V: KVM: Improve privilege mode filtering for perf

[Atish Kumar Patra <atishp@rivosinc.com>]

On Thu, Dec 15, 2022 at 12:18 PM Conor Dooley <conor@kernel.org> wrote:
>
> Hey Atish,
>
> On Thu, Dec 15, 2022 at 09:00:40AM -0800, Atish Patra wrote:
> > RISC-V: KVM: Improve privilege mode filtering for perf
>
> I almost marked this as "not applicable" in patchwork as I was mislead
> by the $subject. I know our perf driver is a real mixed bag, but should
> it not be something more like:
> "perf: RISC-V: Improve privilege mode filtering for KVM"?

Sure. I will change it in the next version.

> It was only when I noticed that the rest of the series had been marked
> as "Handled Elsewhere" that I realised that this must not be a KVM patch
> ;)
>
> Thanks,
> Conor
>
> > Currently, the host driver doesn't have any method to identify if the
> > requested perf event is from kvm or bare metal. As KVM runs in HS
> > mode, there are no separate hypervisor privilege mode to distinguish
> > between the attributes for guest/host.
> >
> > Improve the privilege mode filtering by using the event specific
> > config1 field.
> >
> > Reviewed-by: Andrew Jones <ajones@ventanamicro.com>
> > Signed-off-by: Atish Patra <atishp@rivosinc.com>
> > ---
> >  drivers/perf/riscv_pmu_sbi.c   | 27 ++++++++++++++++++++++-----
> >  include/linux/perf/riscv_pmu.h |  2 ++
> >  2 files changed, 24 insertions(+), 5 deletions(-)
> >
> > diff --git a/drivers/perf/riscv_pmu_sbi.c b/drivers/perf/riscv_pmu_sbi.c
> > index 65d4aa4..df795b7 100644
> > --- a/drivers/perf/riscv_pmu_sbi.c
> > +++ b/drivers/perf/riscv_pmu_sbi.c
> > @@ -298,6 +298,27 @@ int riscv_pmu_get_hpm_info(u32 *hw_ctr_width, u32 *num_hw_ctr)
> >  }
> >  EXPORT_SYMBOL(riscv_pmu_get_hpm_info);
> >
> > +static unsigned long pmu_sbi_get_filter_flags(struct perf_event *event)
> > +{
> > +     unsigned long cflags = 0;
> > +     bool guest_events = false;
> > +
> > +     if (event->attr.config1 & RISCV_KVM_PMU_CONFIG1_GUEST_EVENTS)
> > +             guest_events = true;
> > +     if (event->attr.exclude_kernel)
> > +             cflags |= guest_events ? SBI_PMU_CFG_FLAG_SET_VSINH : SBI_PMU_CFG_FLAG_SET_SINH;
> > +     if (event->attr.exclude_user)
> > +             cflags |= guest_events ? SBI_PMU_CFG_FLAG_SET_VUINH : SBI_PMU_CFG_FLAG_SET_UINH;
> > +     if (guest_events && event->attr.exclude_hv)
> > +             cflags |= SBI_PMU_CFG_FLAG_SET_SINH;
> > +     if (event->attr.exclude_host)
> > +             cflags |= SBI_PMU_CFG_FLAG_SET_UINH | SBI_PMU_CFG_FLAG_SET_SINH;
> > +     if (event->attr.exclude_guest)
> > +             cflags |= SBI_PMU_CFG_FLAG_SET_VSINH | SBI_PMU_CFG_FLAG_SET_VUINH;
> > +
> > +     return cflags;
> > +}
> > +
> >  static int pmu_sbi_ctr_get_idx(struct perf_event *event)
> >  {
> >       struct hw_perf_event *hwc = &event->hw;
> > @@ -308,11 +329,7 @@ static int pmu_sbi_ctr_get_idx(struct perf_event *event)
> >       uint64_t cbase = 0;
> >       unsigned long cflags = 0;
> >
> > -     if (event->attr.exclude_kernel)
> > -             cflags |= SBI_PMU_CFG_FLAG_SET_SINH;
> > -     if (event->attr.exclude_user)
> > -             cflags |= SBI_PMU_CFG_FLAG_SET_UINH;
> > -
> > +     cflags = pmu_sbi_get_filter_flags(event);
> >       /* retrieve the available counter index */
> >  #if defined(CONFIG_32BIT)
> >       ret = sbi_ecall(SBI_EXT_PMU, SBI_EXT_PMU_COUNTER_CFG_MATCH, cbase,
> > diff --git a/include/linux/perf/riscv_pmu.h b/include/linux/perf/riscv_pmu.h
> > index a1c3f77..1c42146 100644
> > --- a/include/linux/perf/riscv_pmu.h
> > +++ b/include/linux/perf/riscv_pmu.h
> > @@ -26,6 +26,8 @@
> >
> >  #define RISCV_PMU_STOP_FLAG_RESET 1
> >
> > +#define RISCV_KVM_PMU_CONFIG1_GUEST_EVENTS 0x1
> > +
> >  struct cpu_hw_events {
> >       /* currently enabled events */
> >       int                     n_events;
> > --
> > 2.25.1
> >
> >