Re: [RFC 4/9] RISC-V: KVM: Improve privilege mode filtering for perf

Sergey Matyukevich
2022-11-09T13:42:48Z

Hi Atish,

> 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.

... [snip]

> +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;

IIUC we should inhibit host counting if we want guest events:
cflags |= guest_events ? SBI_PMU_CFG_FLAG_SET_SINH : SBI_PMU_CFG_FLAG_SET_VSINH;

> + if (event->attr.exclude_user)
> + cflags |= guest_events ? SBI_PMU_CFG_FLAG_SET_VUINH : SBI_PMU_CFG_FLAG_SET_UINH;

Same here.

> + 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;
> +}

Regards,
Sergey