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

[Yicong Yang <yangyicong@huawei.com>]

On 2024/4/11 22:28, Will Deacon wrote:
> 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?
> 

I may misunderstand 'exclude_host' in the doc. Yes we won't include EL0 here
in the driver but we should handle it on guest enter/exit, which is missed
in this patch. Will see how to handle it properly on guest enter/exit and
respin a v3.

Thanks.

_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel