Re: [PATCH v2 3/3] perf: arm_spe: Enable the profiling of EL0&1 translation regime

[Will Deacon <will@kernel.org>]

On Thu, Nov 30, 2023 at 03:46:09PM +0800, Yicong Yang wrote:
> From: Yicong Yang <yangyicong@hisilicon.com>
> 
> On a VHE enabled host, the PMSCR_EL1 will be redirect to PMSCR_EL2
> and we're actually enabling E0SPE and E2SPE in the driver. This means
> the data from EL0&1 translation regime of a VM will not be profiled.
> So this patch tries to add the support of profiling EL0 and EL1 of
> a VM. Users can filter data of different exception level by using
> the perf's exclude_* attributes. The exclude_* decision is referred
> to Documentation/arch/arm64/perf.rst and the implementation of
> arm_pmuv3.
> 
> Signed-off-by: Yicong Yang <yangyicong@hisilicon.com>
> ---
>  drivers/perf/arm_spe_pmu.c | 37 ++++++++++++++++++++++++++++++-------
>  1 file changed, 30 insertions(+), 7 deletions(-)
> 
> diff --git a/drivers/perf/arm_spe_pmu.c b/drivers/perf/arm_spe_pmu.c
> index 09570d4d63cd..a647d625f359 100644
> --- a/drivers/perf/arm_spe_pmu.c
> +++ b/drivers/perf/arm_spe_pmu.c
> @@ -316,21 +316,44 @@ static u64 arm_spe_event_to_pmscr(struct perf_event *event)
>  static void arm_spe_pmu_set_pmscr(struct perf_event *event)
>  {
>  	struct perf_event_attr *attr = &event->attr;
> -	u64 reg = 0;
> +	u64 pmscr_el1, pmscr_el12;
>  
> -	reg = arm_spe_event_to_pmscr(event);
> -	if (!attr->exclude_user)
> -		reg |= PMSCR_EL1x_E0SPE;
> +	pmscr_el1 = pmscr_el12 = arm_spe_event_to_pmscr(event);
> +
> +	/*
> +	 * Map the exclude_* descision to ELx according to
> +	 * Documentation/arch/arm64/perf.rst.
> +	 */
> +	if (is_kernel_in_hyp_mode()) {
> +		if (!attr->exclude_kernel && !attr->exclude_host)
> +			pmscr_el1 |= PMSCR_EL1x_E1SPE;
>  
> -	if (!attr->exclude_kernel)
> -		reg |= PMSCR_EL1x_E1SPE;
> +		if (!attr->exclude_kernel && !attr->exclude_guest)
> +			pmscr_el12 |= PMSCR_EL1x_E1SPE;
> +
> +		if (!attr->exclude_user && !attr->exclude_host) {
> +			pmscr_el1 |= PMSCR_EL1x_E0SPE;
> +			pmscr_el12 |= PMSCR_EL1x_E0SPE;
> +		}

Hmm, I don't understand this part. Doesn't this mean that setting
'exclude_host' to true will also exclude userspace (EL0) profiling for
the guest?

Will

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