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

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Date:   Wed, 9 Nov 2022 16:42:27 +0300
From:   Sergey Matyukevich <geomatsi@...il.com>
To:     Atish Patra <atishp@...osinc.com>
Cc:     linux-kernel@...r.kernel.org, Albert Ou <aou@...s.berkeley.edu>,
        Anup Patel <anup@...infault.org>,
        Atish Patra <atishp@...shpatra.org>,
        Guo Ren <guoren@...nel.org>, kvm-riscv@...ts.infradead.org,
        kvm@...r.kernel.org, linux-riscv@...ts.infradead.org,
        Mark Rutland <mark.rutland@....com>,
        Palmer Dabbelt <palmer@...belt.com>,
        Paul Walmsley <paul.walmsley@...ive.com>,
        Will Deacon <will@...nel.org>
Subject: Re: [RFC  4/9] RISC-V: KVM: Improve privilege mode filtering for perf

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