Re: [PATCH V7 3/6] arm64/perf: Add branch stack support in struct arm_pmu

Anshuman Khandual
2023-02-09T03:42:15Z

On 2/9/23 00:56, Mark Rutland wrote:
> On Fri, Jan 13, 2023 at 09:45:22AM +0530, Anshuman Khandual wrote:
>>
>> On 1/12/23 19:24, Mark Rutland wrote:
>>> On Thu, Jan 05, 2023 at 08:40:36AM +0530, Anshuman Khandual wrote:
>>>> struct arm_pmu {
>>>> struct pmu pmu;
>>>> cpumask_t supported_cpus;
>>>> char *name;
>>>> int pmuver;
>>>> + int features;
>>>> irqreturn_t (*handle_irq)(struct arm_pmu *pmu);
>>>> void (*enable)(struct perf_event *event);
>>>> void (*disable)(struct perf_event *event);
>>>
>>> Hmm, we already have the secure_access field separately. How about we fold that
>>> in and go with:
>>>
>>> unsigned int secure_access : 1,
>>> has_branch_stack : 1;
>>
>> Something like this would work, but should we use __u32 instead of unsigned int
>> to ensure 32 bit width ?
>
> I don't think that's necessary; the exact size doesn't really matter, and
> unsigned int is 32-bits on all targets suppropted by Linux, not just arm and
> arm64.
>
> I do agree that if this were a userspace ABI detail, it might be preferable to
> use __u32. However, I think using it here gives the misleading impression that
> there is an ABI concern when there is not, and as above it's not necessary, so
> I'd prefer unsigned int here.

Makes sense, will this as unsigned int.